Shortest Day Research Articles

Small Poems For The Winter Solstice

SMALL POEMS FOR THE WINTER SOLSTICE / Margaret Atwood A clean page: what shines in you is not nothing, though equally clear & blue and I'm old enough to know I ought to give up wanting to touch that shining. What shines anyway? Stars, cut glass, and water, and you in your serene blue shirt Standing beside a window while it rains, nothing much going on, intangible. To put your hand into the light reveals the hand but the light also: shining is where they touch. Other things made of light: hallucinations & angels. If I reach my hands into you, will you vanish? FREE FALL is falling but at least it's free. I don't even know whether I jumped or was pushed, 18 · The Missouri Review but it hardly matters now I'm up here. No wings or net but for an instant anyway there's a great view: the sea, a line of surf, brown cliffs tufted with scrub, your upturned face a white zero. I wish I knew whether you'll catch or watch. 3. MOUTH TO MOUTH I'm bringing you back to life. Why did you drown like that without telling? What numbed you? What rose over your head was gradual and only everybody's air, standard & killing. Your head floats on your hand, on water, you turn over, your heart returns unsteadily to its two strong notes. I'm bringing you back to life, it's mutual. Towards my chill house in this sloppy weather, hands on the cold wheel, hoping there'll be a fire; slush on the grass, past an accident, then another. Somewhere there's one more, mine. In a minuet we just miss each other, in an accident we don't. Dance is intentional but did you miss me or not, was it too close to the bone for you, was that Margaret Atwood The Missouri Review · 19 pain, am I gone? Nothing's broken, nevertheless I'm skinless, the gentlest touch would gut me. Slowly, slowly, nobody wants a mess. I float over the black roads, pure ice. 5. No way clear, I write on the lines across this yellow paper. Poetry. It's details like this that drag at me, and the nasty little bells on the corners I pass on my way to meet you: singing of hunger, darkness & poverty. 6. The weeks blink out, the winter solstice with its killed pine branches and tiny desperate fires is almost upon us again & again, in fifty versions: the trees turn dull blue, the fields dun for the last time. We have a minute, maybe two in which we're walking together towards the edge of that evergreen forest we'll never enter through the drifted snow which is no colour, which has just fallen, which has just fallen, on which we will leave no footprints. 20 · The Missouri Review Margaret Atwood 7. This poem is mournful & sentimental & filled with complaints: where were you? When I needed you. I'd like to make a bouquet of nice clean words for you, hand it to you and walk away, function accomplished. I can't do it. This is the shortest day of the year, shrunken, blueveined & cold, deafmute. That's me on the corner, sleet down my neck, wordless. Where are you? You think I live in a glass tower where the phone doesn't ring and nobody eats? But it does, they do and leave the crumbs & greasy knives. In the front room dogsmells filter through the door dirty fur coats & the insides of carnivore throats. Neglect & disarray, cold ashes drift from the woodstove onto the floor. Cats with their melting spines festoon themselves in every empty corner. Who's fed them? Who knows? What I want you to see is the banality of all this, even while I write the doorbell pounds down there, constant assaults of the radio, one more blameless crushed face, another pair of boots drips in the hall. Margaret Atwood The Missouri Review · 22 There's no mystery, I want to tell you, none at all, no more than in anything else. What I do is ordinary, no surprise, like you no trickier than sunrise. 9. Some would...

Seasonal effects on the cropping-cycle of lettuce in glass-houses during the winter

Current information about the duration of the lettuce cropping-cycles in glasshouses during the winter is presented as linear functions which provide a simple model for crop planning. The data are also plotted against the date in the middle of each cropping-period, in order to show as accurately as possible the effect of growing-conditions on the duration of the cropping-cycle. Plotting the data in this way is based on the concept that the cropping-cycle depends mainly on seasonal radiation, presented by two-sided linear functions with a maximum value around the shortest day (21 December). The amount of radiation appears to be the dominant factor which determines the length of the cropping-cycle.

Length of the Day in Jaina Astronomy

According to post-Vedānga pre-Siddhāntic Jaina canonical texts, 18 muhūrtas (1 muhūrta = 48 minutes) and 12 muhūrtas are respectively the greatest and the smallest lengths of daylight. The length of any day (daylight) of the year can be computed therefrom through a simple linear zigzag function. However, the ratio 3: 2 between the greatest and the smallest length of daylight holds good for a latitude 35° north very near to that of Babylon. This ratio is also propounded in Jyotisa Vedāngam. It is exposed here that the ratio 3: 2 holds equally good for Gandhāra, a renowned seat of ancient Indian culture. Gandhāra might have been used for purposes like those of a standard station for purposes of time-reckoning in ancient India. However, by applying a correction for the variable rate of flow of water through the orifice of a water-clock, it has been exposed that the actual ratio of maximum and minimum lengths of daylight measured in time-units is different from the ratio of the amounts of water to be poured into the water-clock on the respective days. It is revealed that the ratio 3:2 of the amounts of water to be poured into the water-clock on the longest and shortest days (daylights) is equivalent to the ratio √3: √2 of the actual time-lengths of the longest and the shortest days respectively. It refers to a latitude 19° 6 north, very near to that of Ujjainī, another renowned seat of ancient Indian culture.

Studies on the breeding season of Icelandic ewes and ewe lambs

SummaryThe paper reports on a study, conducted in four successive seasons, of sexual development and breeding activity in females of the Iceland breed, the only breed of sheep kept in the country. The ewe lambs normally attained puberty in their first year of life, on average at 7 months of age, with marked individual variation in both age and body weight at first oestrus. Ewe lambs always showed oestrus on average slightly later than mature ewes (2–9 years), the mean date of onset of the breeding season of the latter being 8 December, however, with considerable individual variation. Furthermore, ewe lambs had a shorter breeding season (1–4 months) than ewes (4–6 months) and they appeared to experience more silent heats resulting in less regular cyclic activity. There seemed to be a minor increase in the duration of the oestrous cycle with age and ewe lambs clearly exhibited shorter oestrus (heat) than ewes. With seasonal breeding activity ranging from November to May the mid-breeding season occurs some 4–7 weeks after the shortest day.

Attainment of puberty and reproductive performance in Clun Forest ewe lambs

SUMMARYCertain aspects of puberal development and reproductive performance in Clun Forest ewe lambs with a wide range of birth dates were investigated during the two seasons 1969–71. Of 33 ewe lambs born in the spring of 1969, 26 exhibited their first oestrus at a mean date of 8 November 1969 ± 2·5 days, the mean age being 228·3 ± 2·4 days and the mean body weight 36·3 ± 0·9 kg. The lambs which failed to breed in their first year, together with lambs born in the autumn of 1969, attained puberty during the autumn of 1970. Twenty-three ewe lambs carried foetuses to term in the spring of 1970 and had a mean lambing rate of 113·0 ± 7%. Of 84 ewe lambs born in the spring of 1970, 73 attained puberty in the first year of life at a mean date of 11 November 1970 ± 2·7 days, the mean age being 223·7 ± 3·0 days and the mean body weight 32·2 ± 0·5 kg. Cyclic activity of ewe lambs born in 1970 was recorded throughout their first breeding season. They experienced their last oestrus of the season at a mean date of 24 January 1971 ± 2·2 days, the mean age being 296·9 ±3·9 days and the mean body weight 32·4 ± 0·6 kg. The mid-breeding season was 18 December 1970, coinciding with the shortest days, and the mean number of heats exhibited throughout the season was 5·15 ± 0·24 per lamb.Marked individual variation existed in age and body weight at puberty and in breeding activity, largely due to differences in date of birth and growth rate during rearing. Ewe lambs born early tended to experience their first oestrus earlier in the season than late born lambs but they did so at a higher age and heavier body weight. Fast growth rate and earliness of puberty were associated with extended duration and enhanced regularity of cyclic activity. Time of birth was clearly of fundamental importance in relation to the onset and duration of breeding activity in the ewe lambs included in the present study.Adult rams of three breeds were found to vary consistently in the proportion of ewe lambs which they detected in oestrus, rams of the lambs' own breed being most efficient.

Breeding and Molt Schedules of the Rufous-Collared Sparrow in Coastal Perú

The Rufous-collared, or Andean, Sparrow (Zonotrichia capensis) occurs from the highlands of the state of Chiapas, M6xico, to Cape Horn, Chile, its range spanning approximately 73 degrees of latitude. Further, it is common over most of its range and is often the commonest small passerine where it occurs. A species with such characteristics is an ideal subject for a series of studies of breeding and molt schedules at various latitudes where the populations are subjected to different photoperiodic regimes. Such comparisons make possible an assessment of the relative and changing importance of photoperiod and other environmental features as proximate (timing) factors in the scheduling of the important events in the annual cycles of a single species in different parts of its range. By so doing, a better understanding of the ultimate (adaptive) factors underlying these various annual cycles in this and other species can be achieved. The first study of the annual cycle of Zonotrichia capensis was made in 1958-59 by the late Alden H. Miller (1959a, 1961, 1962) on a population near Cali, Colombia, at latitude 3' 30' N. There the longest and shortest days of the year differ by only 12 min and photoperiod may be disregarded as a proximate factor. More recently Wolf (1969) has reported on the annual cycle of this species near Las Varas, Costa Rica, at 100 10' N, where longest and shortest days of the year differ by 76 min. The present paper reports on the annual cycle near Chilca, Department of Lima, Perui, in the coastal desert at 120 30' S, where longest and shortest days differ by 91 min.

Effects of shading and time of year on net assimilation rates of young glasshouse tomato plants

SUMMARYMinimum and maximum net assimilation rates were determined from calculated curves of closest fit to data for 2 years. The minimum (14 g./m.2/week) occurred in mid‐December, immediately before the shortest day, and the maximum (78 g./m.2/week) between 27 June and 8 July, just after the longest day. The northern limit at which the tomato cannot maintain vegetative growth under glass in mid‐winter is probably latitude 59–60° and is determined by a limiting daylength of approximately 6 hr. The proportional reduction in net assimilation rate by shading was independent of the time of the year. The photosynthetic system of glasshouse tomato plants is not light‐saturated in midsummer in southern England.

The Deciduous Behavior of a Tropical Plant, Plumeria acuminata

AbstractThe deciduous behavior of the tropical perennial Plumeria acuminata Ait., cultivar Sherman White, was investigated. The temperature during the period of experiment varied only 3°C, the mean maxima and minima, respectively, being; 28.5° and 23.5°C for summer months and 25.5° and 20.6°C for winter months. The length of the day‐light period ranged from 14¼ hours on the longest day in June to 11¾ hours on the shortest day in December.Under naturally prevailing conditions of temperature and day‐lengths, cessation of leaf formation and shedding of foliage occurred during the longer‐night, autumn‐winter months. The shedding was manifested in two stages: from mid‐October to mid‐January there was a slow but steady decrease in the number of leaves per plant, and in late January there occurred an abrupt abscission of all remaining leaves. Light interruptions during the middle of each night prevented a net loss in foliage as well as the en masse shedding in late January.Stem elongation was retarded during the autumn‐winter months, but its rate was fully restored when the long nights were interrupted with artificial light. Flowering was unaffected by day‐length.On the basis of these observations it is concluded that the deciduous behavior of Plumeria and perhaps other tropicals, alike temperate climate species, is governed by photoperiod. Cessation of leaf formation and en masse shedding of foliage are induced by long nights. However, in contrast to temperate zone plants, in which deciduousness is an adaptation against the winter cold and freeze, deciduousness provides tropical plants a survival advantage, perhaps, against seasonally recurring droughts.

Tages- und jahresperiodik der strahlenresistenz pflanzlicher zellen

The outer and inner epidermises of red onion scales of Allium cepa and leaflets of the moss Mnium cuspidatum show a marked diurnal rhythm of their resistance toward α- and u.v.-rays (Figs. 1 and 3). In the onion epidermises a-radiation resistance reaches its maximum at 12 noon, its minimum at 8 p.m. Mnium cuspidatum show the maximum of the α-radiation resistance at midnight and the minimum between noon and 4 p.m. In addition to it the diurnal changes of nuclear sizes of the inner epidermises of onion scales were measured (maximum: 12 noon, minimum: 8 p.m.). The curves parallel each other (Fig. 2). Both the cells of the onion scale and those of the leaflets of various mosses and liverworts also show a marked annual rhythm of resistance to α- and u.v.-radiation (Figs. 4-9). The bryophytes reach their maxima of radiation resistance in June and their minima in December, the onion epidermises are most sensitive to radiation in June and most resistant in December. The nuclear size of the inner epidermises of onion scales show also an annual rhythm beside the diurnal rhythm (Fig. 11). The nuclei reach maximum size in summer, minimum size in winter. While in the diurnal rhythm of the inner epidermises of onion scales the maxima of nuclear size coincide with the maximum radiation resistance of the cells, in the annual rhythm the cells show their greatest radiation resistance when the nuclei are smallest and their greatest sensitivity when the nuclei are largest (Fig. 10). The survival curves of α-irradiated outer epidermises of onion scales show a rapid drop within 24 hr after intensive irradiation, while in epidermises exposed to lower doses of radiation death occurs only after some days. Cell death within 24 hr is believed to be caused by direct damages of the cytoplasm, the slow death after some days, on the other hand, by injuries of the nuclei, which are caused by much lower doses and which have a gradually increasing harmful effect upon the metabolism of the cell. (6,24,25) Our observations refer, unless stated otherwise, to the radiation resistance of cytoplasm within 24 hr. The coincidence in the diurnal rhythm of the maxima of nuclear size and radiation resistance of the cytoplasm seem to contradict the observations of Sparrow and co-workers, (26, 27, 28, 29) according to which plants with smaller nuclear volumes show greater radiation resistance than plants with a bigger nuclear volume. Sparrow's determination of radiation resistance was, however, based on the observation of injury in development and growth made after a long period of time. The irradiation doses used by him were much lower, and he did not determine the radiation resistance of the cytoplasm itself, but the damage indirectly caused by injuries to the much more radiosensitive cell nuclei. Results similar to those of Sparrow could be found in long-term experiments with outer epidermises of red onion scales: at the times when the maximum of nuclear size (9 a.m., 418 μ 2) and the minimum (6 p.m., 339 μ 2) were observed, epidermises of onion scales were exposed to an irradiation series each covering a very wide range of doses (Table 1, Fig. 12, 13). Again, in the case of doses having a lethal effect within 24 hr, the maxima of nuclear size and radiation resistance coincided. After one to three weeks slices with nuclei which were smaller at the time of irradiation (6 p.m. series) now were more resistant than cells with bigger nuclei at the time of irradiation. The larger nucleus in the diurnal rhythm, which is probably more active, seems to have supplied the cytoplasm with substances (enzymes?) which, in spite of heavy damage to the nucleus itself, make it possible for the cytoplasm to survive higher doses within 24 hr. Lower doses, however, which no longer affect the less radiosensitive cytoplasm, damage larger nuclei—in accordance with Sparrow's findings—more than the smaller ones. Experiments concerning the causative factor of the annual resistance rhythm yielded the following results: ( a) On the other hand, the radiation resistance of bryophytes seems to be directly dependent on day length. Experimental shortening of the daylight period in summer with all other conditions remaining constant brought about a marked lowering of radiation resistance (Figs. 16-18). This would correspond to the fact that the maximum of radiation resistance observed in the annual rhythm of bryophytes in June coincides with the longest day of the year and the minimum in December with the shortest day (vice versa in the case of onions).

Seasonal fluctuations in the sexual activity of Awassi, German Mutton Merino, Corriedale, Border-Leicester and Dorset Horn rams:IV. Seasonal changes in the spermatogenic activity of Awassi rams and their relationship to the fructose and citric acid contents of semen

Exhaustion tests were carried out with two Awassi rams 4 times a year for 2 years. The maximum sperm number was obtained in October and the minimum in January. If we consider that the time needed for one spermatogenic cycle and for the migration of the sperm cells through the epid i dymal canal is over 2 months, we may assume that the spermatogenic activity changes with the length of day and reaches its maximum and minimum values during the longest and shortest days, respectively, whereas its androgenic activity is delayed by 3–4 months after the length of daylight changes.

A Consideration of the Seasonal Trends in the Growth of the Fruit of Glasshouse Tomato Plants in Relation to Day-Length

Seed of the Potentate variety of tomato was sown at weekly intervals for 56 weeks and weekly measurements of the diameters of every fruit were made to provide estimates of fruit volume production. Development of the plants could suitably be divided into the following periods : (a) from germination to the start of fruiting, (b) an initial lag in fruit volume production, (c) rapidly increasing production, (d) declining production and (e) arrested development, when fruit swelling virtually ceased.The duration of the period from germination to the start of fruiting was related to day-length.The condition of arrested fruit development occurred from approximately the shortest day to the vernal equinox in mature plants that had already attained a maximal rate of fruit volume production ; in juvenile plants it occurred, and was maintained, from approximately the autumnal equinox to the vernal equinox, i.e. when the duration of darkness exceeded that of the light. In both juvenile and mature plants the condition of arrested fruit development ceased when the duration of the light exceeded that of darkness, and a period of increasing fruit volume production ensued.The rate of fruit volume production during this period of rapid increase was related to day-length and the relation was curvilinear. It continued to increase as long as the days continued to lengthen. When the day-length began to decline so also did the rate of production and the relation with day- length was linear.

The ΚΛΙΜΑΤΑ In Greek Geography

Theclimataplayed an important role in Greek geography. As used in the mathematical geography of Hipparchus and Ptolemy the worddenotes a narrow belt or strip of land, 400 stades wide, on each side of a parallel of latitude; inhabitants of the sameclitmawere assumed to be situated in the same geographical latitude, since, for practical purposes, the celestial phenomena, lengths of the longest and shortest days, and general climatic conditions did not change appreciably within this distance. We may compare the modern conception of arbitrary zones each possessing its own standard time; but whereas these are belts of longitude contiguous to each other, theclimatawere belts of latitude not necessarily contiguous.

Studies on the breeding season and reproduction of the ewe Part III. The breeding season and artificial light Part IV. Studies on the reproduction of the ewe Part V. Mating behaviour and pregnancy diagnosis

During the course of three breeding seasons, daily observations of oestrus were undertaken on the following groups of ewes, all of which were running with ochred rams. One hundred and twenty ewes (pure bred and first-cross) of different breeds and ages, running with vasectomized rams under natural conditions. Twenty-eight grade Suffolk ewes fed on a submaintenance diet. Eighteen grade Suffolk ewes running with a fertile ram. Twenty ewes of several breeds exposed to artificial light.The effects of heredity (breed and individual), environment (season, year and nutrition), age and artificial light on the breeding season and related phenomena have been investigated. The results and conclusions were as follows:1. (a) There are breed differences in the extent of the breeding season, cycle length, incidence of silent heat and duration of heat (Table 29). (b) The duration of the breeding season is related to the geographical origin (latitude and altitude) of the breed, (c) The duration of the breeding season of the first-cross is intermediate between that of the two parents, (d) Individual differences in the number of oestrous cycles per ewe per season were more marked in the mountain breeds.2. (a) Of the ewe lambs, 79% exhibited oestrus during the shortest days only of the first breeding season. Their breeding season is not spread evenly about the shortest day as it is with adults. (b) The occurrence and length of the breeding season in ewe lambs is associated with early birth dates or with higher growth rates.3. (a) Significant differences exist between breeds in the age at first oestrus. (b) Ewe lambs born early in the season showed their first oestrus at later age and heavier weight than those born late.4. Annual differences in the duration of the breeding season, cycle length, incidence of silent heat and occurrence of first oestrus were negligible.5. (a) Submaintenance diet had no effect on the onset of the breeding season, but it converted oestrus into silent heat. Conception occurred less frequently after periods of underfeeding. (b) At high latitudes nutrition has only a minor effect on the breeding season of the ewe.6. (a) A constant high ratio of artificial darkness (8 hr. light: 16 hr. darkness) hastened the onset of the breeding season some 57 and 27 days in the two experimental groups. (b) A constant high ratio of artificial light (16 hr. light: 8 hr. darkness) hastened the end of the breeding season some 104 days on an average (in one experimental group), (c) There were breed differences in the latency of initiation and of cessation of the induced breeding season, (d) In the induced breeding season cycles of ovulation preceded the first oestrus, (e) Two thresholds of pituitary activity are suggested, one for the onset of ovulation, and the other for the manifestation of oestrus.7. (a) A high frequency of cycles outside the normal range (14–19 days) was observed in the mountain breeds and in ewe lambs. (b) The shortest average cycle length coincided with the shortest days of the year.8. A high frequency of silent heats (during the breeding season) was observed in the mountain breeds, in ewe lambs and during the second half of the breeding season.9. Oestrus was of longer duration in adults and yearlings than in ewe lambs.10. (a) Post-partum heat occurred in 56% of Suffolk ewes with an average lactation anoestrus of 35 days. (b) There is a relationship between the early onset of the breeding season and the incidence of post-partum heat, (c) Conception post-partum is partly inhibited by lactation.11. Mating behaviour was observed in animals of several breeds and ages (three patterns were recorded for ewes and eight patterns for rams).12. Irregular columnar cells in the vaginal smear of the ewe characterized late pregnancy.In addition, the breeding season of wild and domestic sheep was reviewed in relation to the environment with special reference to the length of daylight.

Sexual season in ewe lambs.

THE sexual season of ewe lambs lasts only a quarter to a third as long as that of adults1. In ewe lambs, sexual activity starts during November and December in Cambridge (N0)2, while it starts during June in New Zealand (S0)3; and consequently the sexual season coincides with the shortest days of the year irrespective of the hemisphere. Their sexual season, which varies with the breed, is not spread evenly about the shortest day as it is with adults4. The onset of the sexual season in ewe lambs varies with the month of birth2,5; data regarding the cessation or extension of the sexual season are notably lacking.

REPRODUCTION IN THE EWE

Summary1. The relative low prolificacy of the ewe is a factor severely limiting the sheep's ability to compete with other forms of livestock production in intensive agriculture. This article is an attempt to examine critically all the available information on the reproductive physiology of the ewe, with particular emphasis on the factors controlling the various phenomena and the possibility of increasing prolificacy.2. All breeds exhibit, to a greater or less extent, a breeding season which is under light control. Available data on the extent of this season are tabulated.3. The ‘height’ of the breeding season corresponds roughly to the shortest day of the year, and the ‘depth’ of anoestrum to the longest day.4. This and other data suggest a seasonal fluctuation in pituitary gonadotrophic activity controlled by, and roughly inversely related to, the period of daylight relative to dark. It reaches a maximum when the days are shortest and a minimum when they are longest.The ability of some breeds to come into oestrus and conceive shortly after parturition depends on the breeding season being sufficiently long to permit ewes mated early in the season to lamb well before its end. Provided then that the lactation anoestrum, the length of which appears to vary according to the stage of the breeding season, does not run into the true anoestrum the ewes can mate and conceive again while lactating.6. The onset of the breeding season is preceded by an ovulation without heat–‘silent heat’. The evocation of heat with ovulation appears dependent on the presence of a waning corpus luteum.7. Seasonal variation in the reproductive capacity of the ram is evident but is not as marked as in the ewe.8. The literature on the dioestrous cycle, ovulation, fertilization, attachment and subsequent development of the embryo and foetus is reviewed. Very loose attachment to the cotyledons occurs at about 11 days after ovulation, which attachment remains loose up to the 30th day. Full placentation is not completed until the middle of pregnancy.9. Embryonic mortality within the first 21 days accounts for an appreciable number of the ova fertilized. While the number of ova shed is probably the main factor controlling the number of lambs born, this mortality must be considered.10. The use of gonadotropins in anoestrum to obtain early pregnancies is fully discussed and the literature reviewed. While, in general, results have been disappointing there appears to be a definite pattern of behaviour depending on the state of the ovaries at the time of injection.11. An interesting report on the use of pregnant mare's serum (PMS) in inducing fertile matings shortly after parturition within the breeding season is discussed. If this can be confirmed, it may be of value in obtaining two pregnancies within a year.12. The subcutaneous injection of 500 i.u. of PMS 12 days after the preceding oestrus will result in multiple ovulations at the ensuing heat period 4 or 5 days later. However, the individual response to any given level of PMS is extremely variable, from two to nine ovulations having been observed following 500 i.u. Mating at this oestrus results in a high proportion of fertilizations and attachments. Subsequent embryonic mortality within the first 21 days following ovulation results in a reduction in the number of embryos surviving to two or three, occasionally four and rarely five or six. Up to four live young have been obtained at Cambridge and five in Russia. The number of lambs born in a small group of Suffolk ewes treated at Cambridge was greater than in the control group. However, some were born dead and the number weaned was similar in both groups.13. There appear to be breed differences in the number of embryos surviving the first 3 weeks of pregnancy following such PMS treatment, probably due to differences in uterine environment.14. Overstimulation with gonadotropins results in accelerated tubal transport of the ova, with lack of fertilization and complete failure to attach.15. Taking a long‐term view, increase in prolificacy can probably be best obtained by selection for a long breeding season and for multiple births. In most breeds there is sufficient variation in these characteristics to offer considerable hope of success.

Sexual season of the ewe and daylight environment.

AN exact knowledge of the duration of the breeding season of improved breeds of sheep in relation to daylight changes has an important bearing on the export of such breeds overseas, determining the areas in which different breeds can be used. Transferring sheep from one latitude to another even within the same hemisphere has been shown to have an effect on the ovarian rhythm through the change of light environment1,2. J. Hammond, jun.3, states that the breeding season of Suffolks is evenly spaced around the shortest day over a period when the length of daylight is 11½ hours or less. J. Hammond, sen.4, relates breed differences in the duration of the breeding season to the geographical origin of breed. Yeates5 reports that the onset and end of the breeding season occurs 10–14 weeks after the seasonal daylight curve changes over to shorter or longer daylight hours, respectively.

On the breeding season in the sheep

Ewes. There was some variation from year to year in the times of onset and end of the breeding season; on the average it was evenly spaced on either side of the shortest day. Occasionally ewes were served and became pregnant at times well outside the normal limits of the breeding season. Lambs were allowed to suckle the ewes for as long as they would; when lambing occurred more than about 100 days from the start of the season there was no delay in onset of heat in the ewe. When lambing was later there was some delay, but the duration of the lactation anoestrum shortened to a minimum near the middle of the season and then lengthened again.In the first half of the season the period of the oestrous cycle lengthened slowly and steadily; in the second part it became more variable, there was first a slight shortening, but upon the whole it continued to increase in length. From the start of the season the frequency of twinning increased quickly to a peak in about November and then declined for the rest of the season. At the end of the season there was a high proportion of services not fertile.Lambs. Growth in the first 2 months was greatest in those born in May; in the fourth to sixth months it was greatest in the earliest born and least in the latest, the highest weight at 6 months old being reached by those earliest born.

EFFECT OF VARIATION IN LENGTH OF DAY ON GROWTH AND DORMANCY OF TREES

One of the outstanding characteristics of the woody plants that are native to the temperate zone is the periodicity of their growth. This periodicity has commonly been assumed to depend largely if not entirely on the periodicity of temperatures favorable to growth. There are reasons, however, for doubting that temperature is the only important factor affecting the length of the growing season. Even in the tropics where the temperature is always high enough to permit growth, many species show a definite periodicity. In the temperate zone the growing season of most species is relatively short, growth ceasing and in some cases leaf abscission beginning long before the occurrence of frosts. Even evergreen species have a limited growing season which usually ends before the advent of temperatures low enough to check growth appreciably. Furthermore, many species of trees brought into the greenhouse in the summer and kept there during the autumn and winter cease stem elongation and the production of new leaves as soon as trees of the same species that are left out-of-doors. Dormancy in such cases is evidently not the result of decreasing temperature, but is caused by some other factor which operates inside as well as outside the greenhouse. The only such factor which varies with the season is length of day. In the latitude of Durham, North Carolina, where these observations were made, there is a difference of about five hours between the longest and the shortest days of the year and this, difference becomes progressively greater with increasing distance from the equator. As a result of the work of Garner and Allard (6, 7) and others, it is well known that the length of day or photoperiod is an important factor in determining the time of flowering and amount and nature of vegetative growth of many species of herbaceous plants. References to the extensive literature on this subject are given in the papers of Garner and Allard (6,7), Kellerman (11), Laurie and Poesch (16), and Ramaley (21), so no review of the work on herbaceous plants will be made here. Klebs (13) was one of the first to investigate the effects of length of day on woody species. He reported that beech, oak, ash, and hornbeam grew all winter when placed under continuous electric light. Garner and Allard (7) also experimented with several species of woody plants, including apple, yellow poplar, box elder, winged sumac, and smooth sumac. They found that yellow poplar, given daylight supplemented by electric light

GROWTH STUDIES ON FRUITS. RESPIRATION OF TOMATO FRUITS

The measurements of respiration here reported have been made as a part of a general study of the growth of tomato fruits. The fruits used have partly come from plants grown in the open during the regular growing season and partly from plants grown in the greenhouse during the winter. The plants grown in the greenhouse have been supplied with additional light during the period of shortest days. The fruits from these plants have been normal in all respects so that comparisons can be made between fruits grown out of doors and indoors. The experiments have been conducted and the amount of carbon dioxide determined as reported by Hover and Gustafson in another paper (6), except that the length of time of each experiment has been much shorter. In all of the experiments cited only one fruit was used in each container, so that the figures given are not averages for several fruits, but rather values for individual fruits. In all of these experiments the fruits were picked from the vines about a half hour to an hour before the experiment was started.

Star-Land

THE new edition of this popular work on astronomy, based on lectures addressed to a juvenile audience, calls for little remark. A few additional illustrations have been introduced, but we are astonished to find that some of the original diagrams have not been amended. Fig. 17, for example, shows a large sun-spot far outside the sun-spot zone; and Fig. 23 shows the altitude of the sun at noon on the shortest day much too great in comparison with the position indicated for the longest day. If the author's name were unknown, diagrams like these would certainly suggest a want of personal acquaintance with astronomical phenomena.