Mature Sporophytes Research Articles

Moss Capsules as Food of the Harvester Ant, Messor

Harvester ants, Messor spp., were observed feeding on moss capsules in a winter when no other food sources were available. The ants climbed up the seta, gnawed off the capsules and carried them to their nests. In the semiarid region where this phenomenon was observed, suitable climatic conditions for spore maturation are rare, and feeding of ants on moss sporophytes even more strongly reduces reproduction by spores. An ecological study carried out during the years 1977-80 included observations on the harvester ant (Messor spp.) as a seed collector. The locality for research was in the Northern Negev of Israel (20 km NW of Beer-Sheva), in a plain covered by loess, elevation 100 m a.s.l. with average annual rainfall of 250 mm. It is a semiarid annual grassland densely covered by mosses during the early winter. The mosses revive and their spores germinate following the first rain (which may occur between October and January), and they dry out with the desiccation of the upper soil layer. Periods between rains are usually too long to enable mosses to complete their life cycle and produce sporophytes before drying out. Winter of 1979-80 was exceptional in its prolonged and densely spaced rains. Conditions resulting from this were highly favourable for mosses, and sporophytes were formed abundantly. By the end of January and the beginning of February, mosses on the loess plain were bearing mature sporophytes, while phanerogams were still at their vegetative growing stage. The dense tufts of sporophytes that appeared simultaneously made them suitable for predators at a time when no seeds were available. The widespread mosses on the loess plain are Aloina aloides var. ambigua (Bruch & Schimp.) Craig, Crossidium crassinerve De Not., to a lesser extent Bryum bicolor Dicks., and some others. The majority of sporophytes of Aloina mature about two weeks before those of Crossidium (mid-January, instead of the beginning of February). Capsules of both species are borne on a straight seta (the setae of Aloina are longer and have larger capsules than those of Crossidium); in Bryum the seta is inclined. HARVESTING Observed for Aloina aloides, January 15, 1980. Harvesting ants (Messor ebeninus and a few colonies of M. semirufus) climb up the seta, check the capsules with their mandibles (possibly to judge size), turn their body downward and gnaw through the seta at the base of the capsule (Fig. 1, then both fall to the ground. The capsules are then carried to the nests. Observed for Crossidium crassinerve, February 1, 1980. In the meantime, all Aloina sporophytes had been harvested. The ants were found to be active in nearby patches of Crossidium. They climbed up the seta (shorter in this species) but did not turn around before cutting the capsules. Some large ants harvested the capsules while remaining on the ground. In Bryum bicolor, which is sparsely distributed, the inclined capsules were cut off by the ant in the two ways mentioned above, depending on the size of the ant and the sporophytes (Fig. 2). TRANSPORT Observed February 1, 1980. Ants transporting Crossidium sporophytes were seen to form a line, which in one case reached 15 m in length. The average pace of transport of capsules into the nest 007-2745/80/524-525$0.45/0 This content downloaded from 157.55.39.105 on Fri, 07 Oct 2016 04:53:56 UTC All use subject to http://about.jstor.org/terms 1980] LORIA & HERRNSTADT: MOSS CAPSULES 525 ~` 'C ~L ?__ -' ? ~`?t. r; i'~ ~R ?

Patterns of Sporophyte Maturation Dates in the Pottiaceae (Bryopsida)

Patterns of sporophyte maturation dates (SMDs) in the Potti- aceae correlate with sexual condition, latitude, date of regional precipitation maximum, habitat and taxonomic group. Most closely related species have SMDs at about the same time (at the month or season level of resolution), but many species complexes, sections, genera and suprageneric taxa have distinc- tive SMDs that may be used as taxonomic characters. An eurychronic group of mostly dioicous, largely hygrophilic species shows a relatively great dif- ferentiation of SMDs between geographic regions. A review of the literature on sporophyte maturation dates (SMDs) in taxa of the Pottiaceae was undertaken to determine its possible taxonomic value. Major floristic studies of the Bryopsida, since the time of-Hedwig, commonly give the season or month(s) of sporophyte capsule maturity as part of the species description, yet seldom is this characteristic used in distinguishing taxa. Near the turn of the century, several studies (Arnell, 1875, 1905; Grimme, 1903; Krieger, 1915) of moss phenology sought to compare dates of sporophyte maturation in taxa but were handicapped by the small number of species for which information was known. Since then, many floristic studies have included phenological information, and this paper summarizes the data on the family Pottiaceae given in 10 major floristic manuals concerning widely scattered areas of the North Temperate Zone of both Old and New Worlds. The probable intent of early authors was to provide data for mosses comparable to times of anthesis in flowering plants. However, because syngamy in mosses occurs up to one year or more before the date of capsule dehiscence, while in angiosperms it occurs just after anthesis, information about sporophyte maturation dates cannot be directly used to estimate degree of temporal reproductive isolation of taxa by different fertilization times. As has been emphasized by Forman (1965), Greene (1960) and Scott et al. (1976), species-specific variations in time of fertilization and of SMD have been described for relatively few mosses. Forman (1965) and Greene (1960) suggested notational systems for recording phenological stages of the life cycles. Previous large-scale studies comparing times of fertilization and of sporophyte maturation have dealt with only a few species of each of many families of mosses and involve only one or two floristic regions. Grimme (1903) compared Arnell's (1875) data from Scandinavia with that given by Limpricht (1890-1894) for Germany, Austria and Switzerland and found that sporophyte development in German mosses usually took a longer time than did Scandinavian mosses of the same species. Fertilization occurred one or two months earlier in Germany. This was apparently related to the longer growing season of the southern areas. He also concluded from his own obser-

Development of the Archegonium and Embryo in Lophocolea heterophylla

Details of sporophyte development are lacking for many hepat- ics. Thus, these data remain unavailable for taxonomic and phylogenetic con- siderations. Development of the embryo in Lophocolea heterophylla (Schrad.) Dum. was investigated in live material and in serial sections of preserved material. The ontogeny of the archegonium was also observed. The archego- nium of L. heterophylla (Schrad.) Dum. develops in a manner similar to all jungermannias. Unique features are its stalk and the occurrence of paraphyses in the terminal cluster. In the Jungermanniopsida, there are two general trends in early embryo development. The hypobasal cell may give rise to the foot and haustorium or it may give rise to only the haustorium. The embryo of L. heterophylla follows the latter trend. This is in agreement with the majority of reports for members of the Jungermanniopsida. The mature sporophyte in the Jungermanniopsida is extremely regular in its mor- phology. In all cases a distinct foot, seta and capsule are found. Because of the con- servative nature of this phase, specific characteristics of its anatomy and development are important in determining a natural classification of genera and families (Schuster, 1966). As specific anatomical characteristics vary in different genera and families, so also is the early ontogeny of the embryo variable. However, details of sporophyte anatomy and development are frequently unknown, due to inaccessability of material at the proper stage of development. Lophocolea heterophylla (Schrad.) Dum. is cosmopolitan in distribution. Since it is paroicous and forms sex organs throughout the year, it is an excellent species for studies of archegonium and embryo development. Although the hepatic archegonium is very uniform in its development, complete ontogenetic accounts are few. Further, its mature sporophyte generally typifies the anatomy common to the Jungermanniales. These features prompted its use in this study.

Phenology of Selected Bryophytes in Southern Illinois

Maturity indices of Atrichum angustatum (Brid.) B.S.G., Diphys- cium foliosum (Hedw.) Mohr, Trichocolea tomentella (Ehrh.) Dum., Nowellia curvifolia (Dicks.) Mitt. and Lophocolea heterophylla (Schrad.) Dum. popu- lations in southern Illinois are discussed. Indices are based on biweekly ob- servations made over a period of a year and are correlated with vapor pressure deficit, temperature, light quality and quantity and daylength. Depending upon the species, these microenvironmental factors variously affect the veg- etative growth, gametangial formation, fertilization and subsequent growth of the sporophytes. Moisture conditions seem most critical to vegetative growth and survival, and photoperiodism seems to be the dominant factor in gametangia formation. Lophocolea is apparently a day neutral plant in ref- erence to gametangia formation while Diphyscium, Atrichum and Trichocolea are long day plants. Gametangia in Nowellia are also formed under long day conditions but their formation, once initiated, is continuous until dessication of the population. Environment can explain only in part a plant's occurrence in a particular habitat. How a plant responds, both vegetatively and sexually, to climatic and edaphic con- ditions may be as important. Since many bryophytes become dormant during part of the year, their microclimates can reflect both growing and dormancy conditions. Tim- ing of sex organ maturation and spore or gemma release also regulates a species introduction and survival at a particular site. The importance of such growth and reproductive responses to the distribution, radiation potential and evolution of bry- ophyte species necessitates understanding the relationship between phenology and seasonal microclimatic variability. Unfortunately, few such studies exist. Greene (1960) presented an account of gametangial and capsular cycles in six mosses. While pointing out some of the difficulties one may encounter in phenological studies, he also demonstrated the presence of three different sporophyte maturation stages in mosses. Forman (1965), utilizing 103 species from a single Wisconsin loca- tion, presented another system for studying moss phenology which is more simplified than Greene's. Other recent phenological studies of mosses include those by Johnsen (1969) on Orthotrichum anomalum Hedw., Clarke and Greene (1970) on Pohlia nu- tans (Hedw.) Lindb. and P. cruda (Hedw.) Lindb. and Hancock and Brassard (1974) on Buxbaumia aphylla Hedw.

GROWTH INHIBITION IN GAMETOPHYTES AND OAT COLEOPTILES BY THELYPTERIN A AND B RELEASED FROM ROOTS OF THE FERN THELYPTERIS NORMALIS

Gametophytes, when grown in the immediate vicinity of a Thelypteris normalis sporophyte—in soil or in sterile culture on agar—showed a reduced number of cells and an altered gross morphology. This is attributed to the action of the thelypterins, which are inhibitors released from T. normalis sporophytes. Growth inhibition of the gametophytes was greatest when thelypterins were added during early stages of gametophyte development. Removal of thelypterin A permitted resumption of growth. Thelypterin A noncompetitively inhibited auxin‐enhanced elongation of A vena coleoptiles. The growth of T. normalis root segments was not affected by thelypterins. The growth of young sporophytes of T. normalis was inhibited by mature sporophytes.

In vitro Studies on the Reproductive Biology of Riccia crystallina

In Riccia crystallina only a few spores germinated after 3-4 months in 4-5% of the cultures attempted. Cold treatment (8-150C) shortened the dormancy period to 15 days and increased the percentage of germination. In inducing the reproductive phase, temperature again turned out to be the critical factor. Day length did not seem to have much effect so long as a certain mini- mum period of illumination was provided. Fertilization took place in the normal way, and mature sporophytes were produced in vitro.

Genetical Features of Ferns as Contrasted to Seed Plants

pects. As Figure 1 shows, an angiosperm seed is a propagule which develops after meiosis and syngamy have occurred. This propagule contains the results of double fertilization; endosperm tissue and an embryo. Upon seed germination this embryo will develop into a mature sporophyte. The genotype of this sporophyte does not reflect its current isolation but rather is related to the breeding system of the parental sporophyte population. Thus it may be homozygous or very heterozygous. In contrast, an homosporous fern spore is a propagule that develops after meiosis but prior to syngamy. In this case only a single haploid cell is dispersed and upon germination undergoes a series of mitotic cell divisions leading to the development of a haploid, generally autotrophic plant, the gametophyte. This organism is functionally hermaphroditic, simultaneously developing male and female gametangia at some point during its life. Self-fertilization (intragametophytic selfing) results in a single diploid cell, the zygote, which is completely homozygous. This homozygous cell undergoes mitotic cell divisions leading to the development of an embryo and eventually a mature sporopbyte. Thus the establishment of a sporophyte from a single propagule in an homosporous fern results in a completely homozygous individual, whereas in a seed plant the sporophyte genotype may be heterozygous. Because of the above genetic distinctions between a seed and a spore, the evolutionary future of disjunct populations of homosporous ferns and angiosperms might predictably be very different. The angiosperm sporophyte, if it is perennial and dioecious, may live long enough to encounter a sporophyte of the opposite sex, outcross, and form progeny. These resulting progeny in all likelihood would be

The Value of Ferns in an Understanding of the Alternation of Generations

during its life history: the small, simple, haploid gametophyte and the large, morphologically complex, diploid sporophyte. In the typical fern life cycle the two generations are isolated from each other by meiosis and fertilization. The initial cell of the gametophytic generation, the spore, is a product of meiosis occurring in the sporangium on the mature sporophyte. The zygote, the initial cell of the sporophytic generation, forms in the archegonium on the gametophyte by the union of sperm and egg. The successive formation of gametophyte and sporophyte in the typical fern life cycle produces both an alternation of morphologies and levels of ploidy. The heteromorphic alternation of generations in ferns offers numerous opportunities for study. One important question is the understanding of the ontogeny of the alternation. At the present time knowledge about the morphogenetic control of the alternation remains incomplete. Basically, it requires a comprehension of how the same genetic constitution can produce plants of such morphological dissimilarity. It is the role ferns (Filicinae) can play in determining the morphogenetic control of the alternation of generations which will be considered.

Experimental investigations into the controlling effects of light conditions on the development and growth of Desmarestia aculeata (L.) Lamour

Abstract Culture experiments designed to test the apparent correlation between the seasonal behaviour of Desmarestia aculeata and light conditions in the sea suggest that light intensity and daylength interact in their effect on development and growth, and that it is the total quantity of light energy received per day that is important in this resptect. Maturation of gametophytes took place between 54 lx and 1,540 lx mean daily illuminance (MDI) but was inhibited at lower levels. Mean daily . The rate of maturation of gametophytes increased with increasing MDI up to 615 lx. Similarly, the developmental rate of young sporophytes increased with increasing MDI, but there was no light saturation effect up to the maximum of 1,540 lx tested. The ability of gametophytes to produce young sporophytes was not impaired by a period of 93 days at a very low light intensity, since sporophytes developed at once with increased illumination. Marked elongation of regenerating branches on mature sporophytes took place at th...

MORPHOGENETIC STUDIES ON THE FERN TODEA BARBARA. III. EXPERIMENTAL EMBRYOLOGY

DeMaggio, AugustusE. (Rutgers · The State U., Coll. of Pharmacy, Newark, N. J.), and RalphH. Wetmore.Morphogenetic studies on the fern Todea barbara. III. Experimental embryology. Amer. Jour. Bot. 48(7): 551–565. Illus. 1961.—A study of the various stages in the life history of the fernTodea barbara(L.) Moore has shown that young embryos can be removed from the surrounding prothallial tissue, within which they normally develop, and successfully grown in culture. It was possible, therefore, to investigate the manner in which the embryo develops when it is freed from the restraint of surrounding cells. Embryos excised 20 days after fertilization could be grown to mature sporophytes in a liquid culture containing mineral salts and sugar. Younger embryos, excised 17 days after fertilization, required the addition of whole coconut milk or a mixture of sorbitol and inositol, components of the “neutral” fraction of coconut milk, to complete their development. Embryos excised prior to the appearance of the first division wall, 4–5 days after fertilization, did not develop into the usual, 3‐dimensional, diploid or sporophytic plant. Instead they become irregular, rather 2‐dimensional, thalloid structures, remarkably similar to the early haploid or gametophytic plant. These findings are considered in relation to the environmental conditions of growth with particular reference to nutritional and physical factors.

Morphogenetic Studies on the Fern Todea barbara. III. Experimental Embryology

DeMaggio, Augustus E. (Rutgers · The State U., Coll. of Pharmacy, Newark, N. J.), and Ralph H. Wetmore. Morphogenetic studies on the fern Todea barbara. III. Experimental embryology. Amer. Jour. Bot. 48(7): 551–565. Illus. 1961.—A study of the various stages in the life history of the fern Todea barbara (L.) Moore has shown that young embryos can be removed from the surrounding prothallial tissue, within which they normally develop, and successfully grown in culture. It was possible, therefore, to investigate the manner in which the embryo develops when it is freed from the restraint of surrounding cells. Embryos excised 20 days after fertilization could be grown to mature sporophytes in a liquid culture containing mineral salts and sugar. Younger embryos, excised 17 days after fertilization, required the addition of whole coconut milk or a mixture of sorbitol and inositol, components of the “neutral” fraction of coconut milk, to complete their development. Embryos excised prior to the appearance of the first division wall, 4–5 days after fertilization, did not develop into the usual, 3-dimensional, diploid or sporophytic plant. Instead they become irregular, rather 2-dimensional, thalloid structures, remarkably similar to the early haploid or gametophytic plant. These findings are considered in relation to the environmental conditions of growth with particular reference to nutritional and physical factors.

An Occurrence of Gametophytes of Equisetum in Cheboygan County, Michigan

Matzke (1941) found gametophytes of E. arvense L. growing in an empty iron mine pit at Orehill, Connecticut. Of the habitat Mr. Matzke writes, slopes are fairly steep, but the width of the pit is so great that there is little shading of the bottom, except in early morning and late afternoon. Consequently the fine soil at the base becomes alternately inundated in wet weather and more or less baked, though never completely so, in dry periods, cracking into characteristic 'cakes.' It was on this substratum that hundreds of gametophytes were found several hundred yards distant from mature sporophytes. Miss Walker (1921, 1931, 1937) studied the gametophytes of several species, some of which were growing in the wild. Other fairly recent reports on the morphological detail of Equisetum gametophytes include those of Kashyap (1914), Campbell (1930), Goebel (1930), Eames (1936), and Smith (1938). The Colonial Point Hardwoods represents a maplebeech forest climax area. It is only recently that the road shown in Figure 1 was cut through in connection with lumbering operations, and it was in this area that

A Study of the Plastids in the Cells of the Mature Sporophyte of Isoetes

1. The visible structure of the chloroplasts of Isoetes is unaltered by the action of various killing agents. 2. The structure of chloroplast and leucoplast includes a network of grana and connecting fibers. The network is distributed through the stroma of the plastid. 3. The red-staining granules observed in the plastids of Isoetes are refractive hila of young starch grains. 4. The grana are the centers about which starch is deposited within the plastids. 5. There is only one plastid in each "resting" meristematic cell of the sporophyte. 6. Division of the mother plastid within such a meristematic cell begins while the nucleus is still in the metabolic phase. The division of the plastid may initiate nuclear division. 7. The two daughter plastids thus formed function in the formation of the achromatic figure. The fibers of the achromatic figure terminate at the inner surface of each daughter plastid and appear to be attached to that surface. 8. The transition from the broad spindle poles at prophase to the pointed spindle poles at metaphase is brought about by a shortening and bending of the plastids at the spindle poles. 9. Plastids of meristematic cells are variable in form and function. In dividing cells the division of the plastid follows a definite sequence of changes in size, shape, and position until cell division is complete. 10. In maturing cells the plastid and its progeny may divide several times without indication of plastid polarity. The daughter plastids thus formed may metamorphose into the chloroplasts of the mature photosynthetic cell or the starch-containing leucoplasts of storage tissues. 11. Plastid polarity has been observed in all the meristematic regions of the sporophytes of I. macrospora and I. muricata var. braunii. 12. Plastids found in the cells of the mature sporophyte are derived from pre-existing, fully formed plastids. The individuality of the plastid in these cells is at the same level as the individuality of the nucleus.

LYCOPODIUM COMPLANATUM VAR. FLABELLIFORME FERNALD: ITS ANATOMY AND A METHOD OF VEGETATIVE PROPAGATION

Lycopodium1 comnplanatumli var. flabelliformai Fernald is the familiar pine, found on juniper hillsides, on the outskirts of hemlock ravines, and in birch associations. It is a decorative ground cover, and is also used in making Christmas wreaths. It is not a rare plant, and is sold by nurseries. However, in the past, efforts to propagate it have proved singularly unsuccessful; the spores take eight years to develop to a mature gametophyte, and portions of the mature sporophyte transplanted from their natural environment or obtained from nurseries have generally failed to live. The work presented here was undertaken in an effort to discover the cause of this difficulty in the propagation of the mature sporophvte, and, if possible, to overcome it. Very little literature has been found dealing, especially with Lycopodiunm comItplanatunt var. flabelliforme Fernald, although considerable work is available on other species of the genus. Russow (I872) and Jones (1905) present discussions of Lyco podium,n com planaturn var. flabelliformie Fernald, Chamberlain (I932) mentions the similarity of the internal anatomy between root and stem (previously discussed in Russow's paper), and Campbell (I928) refers briefly to Lycopodiunlm corniplanatuin var. flabelliforme Fernald in connection with leaf arrangement and sexual organs. Valuable material about other species (many of which closely resemble L. corplanatullt var. flabelliforme Fernald) may be found in publications of Haberlandt (1914), Engler and Prantl (I902), Campbell (I928), Holloway (I909), Bower (I908), and Jones (1905). The last two named are particularly valuable, and in the introduction to Jones' paper is found a review of material on the genus published up to I905.

MORPHOLOGY OF THE MEGAGAMETOPHYTE AND THE EMBRYO SPOROPHYTE OF ISOETES LITHOPHILA

Isoetes has long been the subject of investigation and discussion, but Hofmeister (io), as a result of his investigations on Isoetes lacustris, gave us in I862 the first detailed account of the life history of the genus; and in most particulars his interpretations have stood as correct up to the present time. He called special attention to the similarities existing between Isoetes and the Lycopods, and pointed out some of the homologies existing between Isoetes and certain Spermatophytes, especially the Conifers. Later morphological studies on Isoetes have been made by Bruchmann (4), Belajeff (2), Kienitz-Gerloff (i i), Farmer (8), Campbell (5), Arnoldi (i), Goebel (9), Scott and Hill (T4), Smith (I5), Stokey (i6), West and Takeda (I7), and, in a limited way, by others. But accounts of detailed studies of the female gametophyte and the embryo sporophyte are pretty well limited to the work of Hofmeister (io), Kienitz-Gerloff (ii), Farmer (8), Campbell (5), and Arnoldi (i). Hlofmeister investigated I. lacustris, a species found in the British Isles and in North and Central Europe. This species, according to Pfeiffer (I3), has megaspores 500-700 microns in diameter. Kienitz-Gerloff also used I. lacustris in his study of the embryo. Campbell worked on I. echinosporca var. braunii (I. brauniii), whose megaspores measure from 420 to 580 microns in diameter. Farmer studied material of I. lacustris, but 'most of his account deals with the development of the organs of the mature sporophyte. Arnoldi made a study of the female gametophyte of I. mtalinvermiana. This form is limited in its distribution to Piedmont, in Italy, and has large megaspores ranging from 66o to 88o microns in diameter. Isoetes lithophila Pfeiffer, used in the present investigation, is apparently limited in its distribution to a sma'l area in Central Texas, and has very small megaspores ranging in size from 290 to 36o microns. The mature gametophyte of this species exhibits a striking abundance o-f rhizoids after the first leaf of the embryo has appeared, as well as a conspicuous protrusion of gametophytic tissue, which for a time encloses the first leaf of the embryo and later remains as a sheath about the base of the leaf until the gametophyte disintegrates. Observation of ftiese prominent features led to the present investigation, and as it progressed, several interesting morpho-

A Study of Preissia quadrata

1. Twelve to sixteen archegonia are borne in each female receptacle, usually three to four in each quadrant, although as many as six were counted in a single quadrant of a receptacle. 2. Although fertilization is probably 100 per cent, the number of mature sporophytes in a single receptacle varies from one to six, the average number for over 100 heads was 2.98, the dominant number being four sporophytes to each head. 3. The sporogenous cells which metamorphose into elaters seem to be sister cells to the spore mother cells; therefore the number of spores is four times the number of elaters. 4. The number of spores to each capsule was estimated at about 3000; the average number for each head, therefore, would be nearly 9000. 5. The spores, although much less numerous than in Marchantia, are decidedly larger. Their diameter is about 75 μ, while the diameter of the spore of Marchantia polymorpha is not over 18 μ. The elaters of Preissia are smaller than those of Marchantia, although their number is greater in...