Total Pollen Production Research Articles

Production and Viability of Pollen and Pollen-Ovule Ratios in Four Rabbiteye Blueberry Cultivars

Fruit set of rabbiteye blueberries (Vaccinium ashei Reade) can be pollen-limited under certain conditions. The objective of this study was to determine production, release, and viability of pollen, as well as pollen-ovule ratios in the rabbiteye blueberry cultivars Austin, Brightwell, Climax, and Tifblue. In vitro tetrad germination varied among genotypes, although, values were high (≥80%) in all cultivars. Pollen viability does not seem to contribute to reproductive failure in the cultivars studied. Total pollen production per flower averaged 8434 tetrads across all cultivars. On a per ovule basis, pollen production was very low relative to other xenogamous species. The low pollen-ovule ratio of rabbiteye blueberry (≈400) may be an indicator of the high efficiency of its pollen dispensing mechanism. Total pollen production varied among cultivars. Furthermore, a significant difference in pollen release was found between two cultivars with similar total pollen production per flower. The possible mechanism regulating pollen release in these cultivars is discussed.

Pollen biology in four Mediterranean Quercus species

Potential pollen production, viability and germination were studied in the most important species of Quercus in the mountains of Córdoba to determine the contribution of each species to the total amount of airborne pollen. The results were compared over two consecutive years with different rainfall patterns. The viability of pollen grains was determined at anther opening, and during the pollination period, in order to determine potential pollination capacity. Results indicated that there were differences in the number of pollen grains produced by stamen in the four species. Equally, there were differences in the number of flowers among the species, being Q. suber the species with higher number of catkins groups and flowers per individual tree. Total pollen production per tree can be summarized in the following proportion: 1: 3: 3: 6 (Q. coccifera, Q. ilex ssp. ballota, Q. faginea and Q. suber). Potential pollen viability was estimated using the Fluorochromatic Reaction (FCR) and a germination assay. The results have shown that Quercus potential pollen viability is high and declines slowly with time. Q. coccifera was the species with the highest percentage of germination, with Q. suber being the lowest.

Pollen production in the Poaceae family

Total pollen production per inflorescence was studied in the most important species of the Poaceae family in the city of Córdoba in order to further our knowledge of the partial contribution of each species of this family to the total amount of pollen released into the atmosphere. The contribution of grasses in a given area was estimated by counting the number of inflorescences in an area of one square meter. Four different representative areas of the city were selected. The number of pollen grains per anther and flowers per inflorescence was also estimated in order to obtain total pollen production per inflorescence. Pollen production per inflorescence ranged from 14,500 to more than 22,000,000 pollen grains, the amount being clearly higher in the perennial species. Pollen production per square meter was higher in the mountains near the city and lower in areas of abandoned crops. Only a few species are responsible for the majority of pollen produced. A phenological study is necessary in order to determine the temporal distribution of this pollen production and subsequent shedding.

Male phenology of three species of Cupressus: correlation with airborne pollen

A 3-year male phenological field study was performed on the represented species of the genus Cupressus in the city of Cordoba (Spain): Cupressus arizonica, C. macrocarpa and C. sempervirens. A new and complete description of the phenological stages of the male flower of Cupressus was obtained. Five phenological phases were described using internal and external bud/flower traits. In general, different pollination periods were recorded for the 3 years. C. arizonica flowered from 20 to 23 days before the others. C. macrocarpa and C. sempervirens flowered almost simultaneously, although the former appeared to flower slightly earlier. The total number of trees per square kilometre was estimated taking into account the total number of trees of each species in the city and surrounding area (5 km radius from the city centre). Data corresponding to total pollen production per tree were taken from a previous study in which the partial contribution of each species to atmospheric pollen was estimated. Considering all these parameters, a theoretical airborne pollen model was proposed. A correlation coefficient (R2) of 0.46 was obtained when comparing this model with the average airborne pollen concentrations for the last 18 years. According to the proposed model, C. macrocarpa trees accounted for 78% of total airborne pollen, while C. sempervirens and C. arizonica accounted for only 18% and 4%, respectively. The final objective of this study was to provide additional biological information on these species responsible for winter pollinosis in the Mediterranean area. Forecasting pollen emission and dispersion has an important application in public health warnings.

Low temperature induced spikelet sterility in rice. I. Nitrogen fertilisation and sensitive reproductive period

Low temperature during panicle development in rice increases spikelet sterility. This effect is exacerbated by high rates of nitrogen (N) application in the field. Spikelet sterility induced by low temperature and N fertilisation was examined in glasshouse experiments to clarify the mechanisms involved. In two glasshouse experiments, 12-h periods of low (18/13�C) and high (28/23�C) day/night temperatures were imposed over periods of 5–7 days during panicle development, to determine the effects of low temperature and N fertilisation on spikelet sterility. In one experiment, 50% sunlight was imposed together with low temperature to investigate the additive effects of reduced solar radiation and low temperature. The effect of increased tillering due to N fertilisation was examined by a tiller removal treatment in the same experiment. Pollen grain number and spikelet sterility were recorded at heading and harvest, respectively. Although there was no significant effect of low temperature on spikelet sterility in the absence of applied N, low temperature greatly increased spikelet sterility as a result of a reduction in the number of engorged pollen grains per anther in the presence of applied N. Spikelet sterility was strongly correlated with the number of engorged pollen grains per anther. Low temperature during very early (late stage of spikelet differentiation–pollen mother cell stage) and peak (second meiotic division stage–early stage of extine formation) microspore development caused a severe reduction in engorged pollen production mainly as a result of reduced total pollen production. Unlike low temperature, the effect of shading was rather small. The increased tillering due to application of high rates of N, increased both spikelet number per plant and spikelet sterility under low temperature conditions. The removal of tillers as they appeared reduced the number of total spikelets per plant and maintained a large number of engorged pollen grains per anther which, in turn, reduced spikelet sterility. The number of engorged pollen grains per anther determined the numbers of intercepted and germinated pollen grains on the stigma. It is concluded that N increased tillering and spikelet number per plant and this, in turn, reduced the number of engorged pollen grains per anther, leading into increased spikelet sterility under low temperature condition.

Response of an allergenic species, Ambrosia psilostachya (Asteraceae), to experimental warming and clipping: implications for public health

We examined the responses of an allergenic species, western ragweed (Ambrosia psilostachya DC.), to experimental warming and clipping. The experiment was conducted in a tallgrass prairie in Oklahoma, USA, between 1999 and 2001. Warming increased ragweed stems by 88% when not clipped and 46% when clipped. Clipping increased ragweed stems by 75% and 36% in the control and warmed plots, respectively. In 2001, warming resulted in a 105% increase in ragweed aboveground biomass (AGB), and the ratio of ragweed AGB to total AGB increased by 79%. Dry mass per ragweed stem in the warmed plots was 37% and 38% greater than that in the control plots in 2000 and 2001, respectively. Although warming caused no difference in pollen production per stem, total pollen production increased by 84% (P < 0.05) because there were more ragweed stems. Experimental warming significantly increased pollen diameter from 21.2 μm in the control plots to 23.9 μm in the warmed plots (a 13% increase). The results from our experiment suggest that global warming could aggravate allergic hazards and thereby jeopardize public health.

Pollen Mobilization in Selected Cucurbitaceae and the Putative Effects of Pollinator Abundance on Pollen Depletion Rates

Very little is known about the rate at which pollen grains are mobilized within insect-pollinated crop systems, and this is especially true the for commercial production of field-grown cucumber (Cucumis sativus L.), monoecious muskmelon (Cucumis melo L.), and triploid watermelon [Citrullus lanatus (Thunb.) Matsum. &amp; Nakai]. The rates of pollen depletion for these crops were therefore investigated on plots simulating commercial crop production using a mixed honey bee (Apis mellifera L.) and bumble bee (Bombus impatiens Cresson) pollinator complex. At anthesis, staminate cucumber, muskmelon, and watermelon flowers contained on average 10539, 11176, and 30739 pollen grains/flower, respectively. At the time flowers closed in the early afternoon (1300 to 1400 hr), only 61% of the total pollen produced had been removed from staminate cucumber flowers, 44% to 62% from muskmelon, and 81% from watermelon flowers. The results suggest that total pollen production in these crops may not necessarily reflect total pollen availability to floral visitors (bees). However, of the total amount of pollen actually removed per flower, &gt;57% occurred during the 2 h following flower anthesis of cucumber and muskmelon, and &gt;77% occurred during the 2 h following flower anthesis of watermelon. Thus, most of the accessible pollen was removed shortly after anthesis, which is when these crops are most receptive to pollination. Nonviable triploid and viable diploid watermelon pollen were removed at similar rates (P = 0.4604). While correlation analyses were not possible for the influence of variable bee abundance on pollen depletion rates, higher bee populations in one year appeared to increase the rate at which pollen grains were removed from staminate flowers.

Mycorrhizal infection and high soil phosphorus improve vegetative growth and the female and male functions in tomato

Summary • To further characterize the effects of mycorrhizal infection and soil phosphorus (P) availability on plant fitness, this study examined their effects on the female and male functions, as well as vegetative growth of tomato ( Lycopersicon esculentum ). • Two cultivars of tomato were grown in a glasshouse under three treatment combinations: nonmycorrhizal, low P (NMPO); nonmycorrhizal, high P (NMP3); and mycorrhizal, low P (MPO). • Mycorrhizal infection and high soil P conditions improved several vegetative (leaf area, days until first flower and leaf P concentration) and reproductive traits (total flower production, fruit mass, seed number and pollen production per plant, and mean pollen production per flower). In general, mycorrhizal and P responses were greater for reproductive traits than vegetative traits. In one cultivar, these responses were greater for the male function than the female function. • Thus, mycorrhizal infection and high soil P conditions enhanced fitness through both the female and male functions. Similar trends were usually observed in the NMP3 and MPO treatments, suggesting that mycorrhizal effects were largely the result of improved P acquisition.

Production of allergenic pollen by ragweed ( Ambrosia artemisiifolia L.) is increased in CO 2-enriched atmospheres

The potential effects of global climate change on allergenic pollen production are still poorly understood. To study the direct impact of rising atmospheric CO2 concentrations on ragweed (Ambrosia artemisiifolia L.) pollen production and growth. In environmentally controlled greenhouses, stands of ragweed plants were grown from seed through flowering stages at both ambient and twice-ambient CO2 levels (350 vs 700 microL L(-1)). Outcome measures included stand-level total pollen production and end-of-season measures of plant mass, height, and seed production. A doubling of the atmospheric CO2 concentration stimulated ragweed-pollen production by 61% (P = 0.005). These results suggest that there may be significant increases in exposure to allergenic pollen under the present scenarios of global warming. Further studies may enable public health groups to more accurately evaluate the future risks of hay fever and respiratory diseases (eg, asthma) exacerbated by allergenic pollen, and to develop strategies to mitigate them.

Pollen productivity variations. Pollen-ovule ratio and sexual selection in Pinus roxburghii

Total pollen production, pollen-ovule ratio and the production of male-female strobili were recorded in Pinus roxburghii at two different altitudes during two successive years. The values of total pollen production per tree and per hectare varied between 1953.56 to 2727.16 2 10 9 and 2.91 to 4.26 2 10 14 (in 1999) at the lower altitude and 1247.5 to 1673.5 2 10 9 and 2.24 2 10 14 (in 1998) and 1599.89 to 2038.96 2 10 9 and 3.18 2 10 14 (in 1999) at the higher altitude. The pollen-ovule ratio in P. roxburghii has indicated the xenogamous type of breeding system The production of male and female cones per tree and per hectare ranged from 21.7 - 0.34 to 33.6 - 0.71 2 10 3 and 55.16 - 24.08 to 220.85 - 87.75 per tree and 32.55 to 70.56 2 10 5 and 2.76 to 26.50 2 10 3 per hectare respectively. However the production of female cones per 100 male cones oscillated between 0.25 to 0.66, which suggested the intense male competition among trees to pollinate their neighbours. A linear correlation was recorded between diameter and extent of the tree crown to the total production of strobili groups/strobili clusters, strobili, microsporophylls and pollen grains per individual tree. The ratio between the number of strobili per strobili group and the number of strobili groups per tree showed an inverse relationship; thus, the individuals with most strobili groups have the strobili groups with the least strobili and vice-versa. This ratio was also shown between the number of pollen grains per strobilus and the number of strobili per tree, as well as the number of pollen grains per strobili group and the number of strobili groups per tree.

Prediction of the beginning of the olive full pollen season in south-west Spain

Given the clinical and agricultural importance of the olive in SW Spain, we have carried out a study to predict the starting date of its full pollen season. The study covers 6 years of meteorological and palynological observations — the latter using a Cour sampler installed in Huelva (SW Spain). The results obtained show that olive full pollination begins when the plant has accumulated 731°C of daily temperature above 5°C from the end of its dormant period. The mean duration of this accumulation was 83 days. A positive relationship has been found between mean temperature of the months before the pollen season (February and March) and the date when the season starts (April). From the data available, rainfall registered between 1 September and 31 March (both before pollination), does not affect the starting date of the full pollen season, but can affect total pollen production, particularly in years with prolonged drought.

Pollen Removal and Deposition by Specialist and Generalist Bumblebees in Aconitum septentrionale

Pollen removal and deposition was studied in the specialised pollination mutualism between the perennial, partly self-incompatible, herb Aconitum septentrionale (Ranunculaceae) and the long-tongued specialist bee Bombus consobrinus (Apidae). Aconitum septentrionale was also visited by three less abundant generalist bumblebees. Bombus consobrinus was also visiting a few other plants before and after flowering of A. septentrionale. Workers of specialist and generalist bumblebees removed similar amounts of pollen per visit. Queens of the specialist species removed less than worker bees. Flower visit duration was the same for queens as for workers of the specialist. However, both workers and queens of the specialist made shorter visits and thus removed more pollen per unit time than did the two most frequent generalists. Thus the specialist showed a higher efficiency (net energy gain per unit time) as a harvester than the generalists. The proportion of the total pollen production removed by the specialist was similar to that found in other mutualism studies. The proportion of the variation in amount of pollen left in a flower after a visit that could be explained by the combined effects of total pollen production per flower and flower visit duration was less for B. consobrinus than for the two most frequent generalists and also less than seen in other comparable studies in the literature. Workers of B. consobrinus were the only abundant depositors of pollen in flowers of A. septentrionale. Visit duration to female phased flowers explained most of the variation in number of pollen deposited on stigmas. 1% of total pollen production reached conspecific stigmas. Thus B. consobrinus was the only quantitatively important pollinator of A. septentrionale.

Pollen production in anemophilous trees

Abstract A study was made of the total pollen production per individual tree in ten anemophilous arboreal species (including wild, cultivated and ornamental species) of considerable aerobiological importance: Pinus pinaster, Ulmus minor, Juglans regia, Platanus hispanica, Quercus rotundifolia, Salix atrocinerea, Populus nigra, Acer negundo, Olea europaea and Fraxinus angustifolia. For each species three isolated well-shaped specimens of medium height were chosen, and the number of flowers per individual tree and the number of pollen grains per anther was estimated. The values of total pollen production varied between a little over 1000 million grains in Juglans regia and more than 500,000 million in one single tree in Quercus rotundifolia. For the production of pollen grains per anther, the values oscillated between 3000 grains in Juglans regia and 100,000 in Olea europaea. There is an exponential correlation between the size of the anthers and the number of pollen grains they contain. A linear correlation is also evident between the volume of the tree crown and the total production of inflorescences, flowers, anthers and pollen grains per individual tree. Based on this, a mean coefficient of the number of grains/meter of diameter of the tree crown is obtained which varies between 3.4 × 108 for Juglans regia and 550.9 × 108 for Quercus rotundifolia. The ratio between the number of anthers per inflorescence and the number of pollen grains per anther carries out a hyperbolic function; thus, the inflorescences with the most anthers have the anthers with the least pollen and viceversa. This ratio is also manifest between the number of grains per flower and the number of flowers per tree, as well as the number of grains per inflorescence and the number of inflorescences per tree.

VARIATION IN POLLEN SIZE, FERTILIZATION ABILITY, AND POSTFERTILIZATION SIRING ABILITY IN ERYTHRONIUM GRANDIFLORUM.

The mean volume of pollen grains and total pollen production varied both within and among plants of Erythronium grandiflorum. The second flowers of two-flowered plants tended to produce smaller and fewer grains than first flowers, but there was no overall relationship between mean pollen grain size and production per flower. I evaluated the effects of pollen size differences within and among plants on two components of male reproductive success: pollen tube growth and postfertilization siring ability. Pollen tubes grown in media were longer for second flowers, but were not correlated with the mean size of pollen grains, suggesting that (1) internal resource content of pollen (i.e., carbohydrates plus lipids) was not associated with the hydrated size of pollen, and that (2) pollen from second flowers contained more resources. I analyzed the growth rate and the fertilization ability of pollen growing in styles. Growth rate differed among donors and recipients, but no effects of pollen or donor characters (i.e., pollen production, grain size, and flower position) were detected. In single donor pollinations, pollen size was negatively correlated with fertilization ability across donors, and positively correlated with postfertilization siring ability of donors. A second experiment used pairs of donors; within-plant differences in pollen size and flower position had effects similar to the single donor experiment on fertilization ability, but among-plant differences were not significant. The results corroborate earlier experiments that suggest that the growth of pollen tubes in the style is probably controlled by the recipient, since donor characters had minimal effects on pollen fertilization ability. Postfertilization siring ability was not affected by within-plant differences in mean grain size and production. For among-donor differences, the number of seeds set for each donor was positively correlated with the mean grain volume, and when a donor producing large pollen fertilized ovules in an ovary, there was increased seed abortion for seeds in the same ovary sired by a second donor. In addition, the total number of seeds produced by a fruit was decreased when both donors had large pollen, apparently due to increased postfertilization abortion. Postfertilization processes appear to be influenced by paternal differences that are expressed through competition among developing seeds for maternal resources.

How much pollen can thrips destroy?

ABSTRACT. 1. A laboratory technique for measuring the number of pollen grains consumed by thrips is described.2. Thrips imaginis Bagnall and Thrips obscuratus (Crawford) (Thripidae) were studied particularly on pollen of the kiwifruit Actinidia deliciosa (A. Chevalier) Liang &amp; Ferguson in New Zealand, and Echium plantagineum L. in Australia.3. Mean daily feeding rates (in grains per thrips per day) ranged from 29 to 843, with an individual rate as high as 1626 for T.imaginis larvae II on E. plantagineum.4. The time taken to feed on a single grain was proportional to grain volume, and decreased with temperature.5. Daily feeding rates were significantly different between pollens, and were higher for smaller grains. The total volume of pollen contents consumed and the total time spent ingesting this volume per thrips per day may be constant with respect to pollen species.6. Daily feeding rates were equivalent to 0.2–0.7% of the average total pollen production of a flower per thrips per day.7. Extrapolation of the daily feeding rates suggests that pollen damage by thrips could sometimes be reducing crop yield or plant fitness.

Effects of Water Stress on Pollen of Phaseolus vulgaris L.

Abstract Pollen of plants of Phaseolus vulgaris L. ‘Red Mexican’ is affected adversely by water stress. The critical stress period occurs 10-13 days after emergence, during the transition from the vegetative to the reproductive phase of development. The transition phase is characterized by the presence of tiny green buds (&gt;0.5-2.0 mm in length), bearing anthers that contain tetrads or free microspores. Pollen abortion of plants stressed during the transition phase is significantly higher than that of pollen from nonstressed plants or from those stressed during later phases of reproductive development. The percentage of pollen germination and total pollen production also are reduced in transition phase-stressed plants. Exine development is abnormal. This abnormal development is particularly interesting because the exine is regarded as so genetically stable that it is regularly used for species identification. Results of these experiments raise questions about the infallibility of identifications, since an environmental stress (such as water) imposed at a critical time of gametophytic development can markedly alter exine patterning.

Late Quaternary vegetational history of the Enga province of Upland Papua New Guinea

Late Quaternary vegetational history of the Enga province of Upland Papua New Guinea

Interaction of Genetic Factors for Fertility Restoration in Hybrid Wheat1

Four different sources of genes for fertility restoration in wheat, Triticum aestivum L. em Thell., were intermated to study the interaction of these genes in the heterozygous condition compared to their homozygous parents. Parents and hybrids were evaluated for pollen production and dispersal in the laboratory on excised spikes from plants grown under field and greenhouse environments. Seed set was also evaluated in diverse controlled environments.Parental restorer sources showed variation for pollen production and dispersal as well as for seed set. Hybrids heterozygous for restorer genes from single sources were inferior to their homozygous parents and to the restorer ✕ restorer hybrids. Most combinations of the different sources of fertility restoration in the hybrid were equal or superior to their homozygous parents for pollen production and dispersal and for seed production. The best combinations of restorers were of Triticum timopheevi/ *3‘Marquis’ parents with parents TBR 26 or TBR 76.Both general combining ability and specific combining ability were highly significant for pollen production characters and for seed set. General combining ability for all characters except total pollen production made up the major portion of the total genetic variability.

Behaviour of a sex-differential fertility gene in hermaphrodite populations

In genera of flowering plants that contain closely related gynodioecious and near dioecious species, near dioecy has probably evolved from gynodioecy by gradual reduction of seed set on hermaphrodites, caused by the action of several genes for partial female sterility. A literature survey shows that several types of sex-function differential fertility effects are widespread in hermaphrodite plants, so that a model of such variation may be of interest both as a model of normal hermaphrodite populations, and for the above evolutionary process. Such a model is presented where there is a dominant or non-dominant gene p for partial female sterility (ovule fertility values w3, w5 t1. Numerical results are given for equilibrium populations and include some cases of complete female sterility for comparison. These results show that frequencies of subhermaphrodites decrease with increased selfing. The heterozygous subhermaphrodite is the fittest, and the homozygous subhermaphrodite the least fit genotype. The fitness of the heterozygous subhermaphrodite decreases, and that of the hermaphrodite increases, with increased selfing. Except for males, proportions of ovule offspring decrease with increased selfing, and again with this exception and with t1 ≠ 1, t2 is highest for heterozygous subhermaphrodites, and for this type is > t1 whereas t2 is least for hermaphrodites. The total ovule production of the population increases, and total pollen production decreases, with increased selfing.

Studies in hay fever: Clinical observations including a botanical and air survey of the Utah region

A study of the literature showed that the cause of hay fever varies widely in different sections of the country and that there is no uniformity in the atmospheric pollen concentration. It has been found, therefore, of increasing importance to make botanical surveys of the patients' environment, including the plant distribution and pollen production as well as the sensitivity of the patients. Many such studies have been made throughout the United States and Europe. Blackley's studies, published in 1873 and 1880, are outstanding pieces of research on hay fever. To Blackley belongs the credit for the method of pollen determination now still in use and also the method of cutaneous testing for the sensitivity of patients. Scheppegrell in 1917 devised a formula for the determination of the pollen content of the air, in grains per cubic yard, and this has been used by many investigators, but, because ragweed pollen is the chief cause of hay fever, practically all the reports thus far published have stressed the ragweed pollen content of the air. Since no reports were available regarding the wind-borne pollens of the Rocky Mountain region, I made botanical and air analysis studies in 1928, 1929, and 1930. Six test plots were chosen in which flora representative of the entire intermountain states was found; that is, alkali flat, desert, swamp, canyon, farming land, and high-grade residence property. From the results (Table I) it was evident that ragweed was neither the most abundant plant in the region nor the chief cause of hay fever as determined by cutaneous tests on hay fever patients. A total atmospheric pollen survey of Utah as a typical intermountain state was undertaken, therefore, rather than merely a ragweed survey. Pollen counting stations were established in four Utah towns. The results were graphed (Chart 1) and showed that the peaks of pollination fell in late July and early August when the grasses were beginning to wane and the weeds reached their maximum. Secondary peaks occurred in September when the sages pollinate. The total pollen production was estimated for the plants found (Table II). The most important anemophilous plants of this region proved to be as follows: (1) Graminaceae. (2) Chenopodiaceae—Russian thistle, salt bush, summer cypress. (3) Artemisia—sages. (4) Ambrosiaceae—ragweed. From cutaneous tests on 1,801 hay fever patients in this area, it was determined that 54.4 per cent of them reacted to the pollen of Russian thistle, 33.7 per cent to sagebrush and 31.4 per cent to common ragweed (Table III). The pollen abundance and the reactions of patients were compared, as below. PER CENT REACTING POLLEN RATING TO 2 PER CENT POLLEN EXTRACT Russian thistle 150 54.4 Sagebrush 130 33.7 Common ragweed 100 31.4 Timothy 40 26.4 Marsh elder 50 25.2 Blue grass 160 24.1 Box elder 35 21.1 Lambs quarter 20 19.1 A scratch reaction of 1:5,000 histamine was used as a positive control and no reactions from cutaneous scratch tests smaller than the histamine wheal were regarded as positive. Scrub oak was proved to have low toxicity. The box elder in spite of low abundance and pollen production accounted for 21.1 per cent of the patients. The fact that ragweed is not so important a factor in the hay fever of this region is due to its low distribution. The sensitivity tests on patients are shown in Table IV which demonstrates the high percentage of patients sensitive to more than one pollen and the low percentage of those whose hay fever is due to a single pollen. There is a considerably higher percentage sensitive to weed pollen than to tree or grass pollen, while nearly a third are sensitive to more than one group. In connection with this work an incidental study was carried on with regard to the effect of travel on hay fever symptoms. Pollen counts were made on vehicles of various types to determine the amount of pollen entrapped on petrolatum-coated slides. All counts were equated to a twenty-four-hour basis for purposes of comparison. Using the counts obtained in Salt Lake City as unity the following ratios for pollen concentration were obtained: Pullman coach 2.7 Chair car 3.8 Automobile 4.7 Electric train 6.2 Locomotive cab 7.2 Observation platform 8.0