Experiments conducted for three years in the greenhouse and for two years in the field at Manhattan, Kansas, proved that heavy infections of leaf rust greatly reduced the yield of wheat. In the greenhouse, the yield of Malakof CI 4898, a susceptible variety, was reduced 55.71%, while a reduction of 22.30%, was noted for Fulhard CI 8257, a resistant variety. In the susceptible variety, the loss in yield was due principally to a reduction in the number of kernels produced, although there also was a slight reduction in the number of heads per plant and in the size of the individual kernels. The loss in yield in a resistant variety, such as Fulhard, probably is due to the killing of many of the green leaf cells. This is visibly expressed in the form of flecking. In these experiments the loss in yield in the resistant variety was about one-third of that in the susceptible variety. No shriveling of the grain resulted from heavy leaf rust infection in the greenhouse. The seed from inoculated plants frequently contained many small kernels. These, however, were plump and well formed. Experiments conducted in the field with Prelude spring wheat and Turkey winter wheat substantiated the results of the greenhouse experiments. Partial control of rust in field plats by sulfur dusting at two-day intervals during the late spring resulted in an increase of 1.7 bushels per acre for Prelude and 2.3 bushels per acre for Turkey. Field experiments also indicated that at least part of the reduction in yield due to leaf rust was caused by the smaller size of individual kernels of the infected plants.

Due to the increasing importance of the wheat disease 'tarwehalmdoder' in the Netherlands, research was started on its occurrence and cause. An extensive literature review proved the identity of 'tarwehalmdoder' with take-all or whiteheads, which were caused by 0. graminis. The symptoms of the disease were root rot, decreased growth with drying of the leaves, blackening of the stem base and premature ripening.Other fungi found on the stubble of Ophiobolus-diseased plants were described.Ascosporous isolates of O. graminis and O. herpotrichus in pure culture were used in artificial inoculations. Inoculation with 0. graminis resulted in whiteheads. Only about half the isolates of O. herpotrichus were virulent on wheat and barley causing death of seedlings. This symptom was different from foot-rot and root-rot.The occurrence of O. graminis on many Gramineae was reported. Resistance did not occur in existing wheat varieties. Environmental factors influenced the severity of the disease. Good crop rotation and cultural practices could limit economic losses.

Due to the increasing importance of the wheat disease 'tarwehalmdoder' in the Netherlands, research was started on its occurrence and cause. An extensive literature review proved the identity of 'tarwehalmdoder' with take-all or whiteheads, which were caused by 0. graminis. The symptoms of the disease were root rot, decreased growth with drying of the leaves, blackening of the stem base and premature ripening.Other fungi found on the stubble of Ophiobolus-diseased plants were described.Ascosporous isolates of O. graminis and O. herpotrichus in pure culture were used in artificial inoculations. Inoculation with 0. graminis resulted in whiteheads. Only about half the isolates of O. herpotrichus were virulent on wheat and barley causing death of seedlings. This symptom was different from foot-rot and root-rot.The occurrence of O. graminis on many Gramineae was reported. Resistance did not occur in existing wheat varieties. Environmental factors influenced the severity of the disease. Good crop rotation and cultural practices could limit economic losses.

cum laude graduation (with distinction) | Due to the increasing importance of the wheat disease 'tarwehalmdoder' in the Netherlands, research was started on its occurrence and cause. An extensive literature review proved the identity of 'tarwehalmdoder' with take-all or whiteheads, which were caused by 0. graminis. The symptoms of the disease were root rot, decreased growth with drying of the leaves, blackening of the stem base and premature ripening. | Other fungi found on the stubble of Ophiobolus-diseased plants were described. | Ascosporous isolates of O. graminis and O. herpotrichus in pure culture were used in artificial inoculations. Inoculation with 0. graminis resulted in whiteheads. Only about half the isolates of O. herpotrichus were virulent on wheat and barley causing death of seedlings. This symptom was different from foot-rot and root-rot. | The occurrence of O. graminis on many Gramineae was reported. Resistance did not occur in existing wheat varieties. Environmental factors influenced the severity of the disease. Good crop rotation and cultural practices could limit economic losses.

The results on hybrid vigor in kernel weight among wheat crosses reported in this paper were obtained from 107 crosses among 28 lines and varieties of common wheat. These crosses included 7,527 selfed and 5,730 crossed kernels. When produced on the same spikes as selfed kernels, crossed kernels averaged 8% smaller and when produced on different spikes 10% smaller than selfed kernels. Selfed kernels were, as an average, about 5% larger than "incrossed" kernels, suggesting a slight error due to the method of crossing. Only 17% of the crosses studied showed some degree of increase; all others showed decreases of crossed as compared with selfed kernels, 22% of which were mathematically significant. Though the 2-year and 3-year data showed some inconsistencies, a general decrease in weight of crossed as compared with selfed kernels was evident. In general, the experiments reported in this paper showed no significant increase in kernel size which could be attributed to the phenomenon of xenia.

In a 4-year grain rotation, on a fertile soil, the accumulations of nitrogen during the period of sod, brought about by non-symbiotic fixation, together with that supplied by the clover roots, is sufficient to meet the normal demands of the grain crops. This is true only when lime, phosphorus, and potassium are liberally supplied. Thus in 40 years the application of 1,440 pounds of nitrogen on plat 28 has resulted in a total increased yield of only 62 bushels of corn, 16 bushels of oats, 68 bushels of wheat, and 1,400 pounds of hay in excess of the PK treatment. This is true in spite of the fact that no lime was used during the 40-year period. The fact that nitrogen is not a serious limiting factor in such a rotation is further emphasized when it is realized that a total of 1,440 pounds of nitric nitrogen applied during the 10 rotations has caused total increased yields of only 12 bushels of corn, 3 bushels of oats, 27 bushels of wheat, and 70 pounds of hay in excess of an application of 480 pounds of nitrogen applied to plat 26. The results of a supplementary phosphate experiment suggest that heavier applications of superphosphate on the PK and PKN treatments would have brought about a somewhat higher level of crop yields which, in turn, would have resulted in a more economic utilization of the applied nitrogen. It is true, however, that the major limiting factor for crop production is that of moisture distribution during the growing season rather than the lack of plant food. Thus, in 1928, when ample rain fell during the summer months, plat 28 produced 82.7 bushels of corn compared to an average annual yield of 58.3 bushels.

The present piece of work deals with the externa morphology of two species of thrips, Aptinothrips rufus and Limothrips cerealium; and the internal anatomy of some of the species representing the two suborders of Thysanopter, Aptinothrips rufus Gmelin, is the common grass inhabiting species and occurs either singly or mixed up with its variety stylifera Trybom. These two varieties are chiefly distinguished by the number of antennal joints. Females are found throughout the year. Males are very rare and only few A4rufus males were collected. No stylifera males were found by me. The larvae also occur on grass and are common. pre_pupae and pupae are found with great difficulty. No male larval, pre-pupal or pupal stages ever came to notice. The other species, Limothrips cerealium Haliday, is the well known corn thrips, which has been believed to cause sterility in oats and wheat. It is found during spring and summer on grasses, wheat and oat plants. The eggs are laid in slits made in leaves and the larvae after hatching go inside the leaf-sheaths or ears of corn. Almost all the stages are found simultaneously on wheat and oat plants in summer. A review of the previous literature shows that except a short description of adult stages, the young forms of A. rufus, and L. cerealium have never been completely described. The female pre-pupae of A. rufus and the male pre-pupae and pupae of Limothrips cerealium are described here for the first time. The collection of Aptinothrips rufus revealed the presence of certain unusual antennal deformities, which are also described here in detail. The mouthparts of L. cerealium were studied, and are described here, establishing the homology as far as possible. A short note on the embryology of L. cerealium is also included. The internal anatomy of Thysanoptera has been very little studied. This is partly due to the minute size of insects. Most of what is known is due to the pioneer work of Jordan (1888), Uzel (1895) and Buffa (1898). In 1915, Peterson made a study of the salivary glands and head-glands in H. femoralis and Cepha.lothrips quccae. In 1926, Klocke published a paper on the anatomy and histology of Thysanoptera. But his work does not present a connected view of the different internal parts. Ten common species were taken for dissection purposes which are :- AEOLOTHRIPIDAE :_ 1. Melanthrips fuscus(Sulzer). THRIPIDA.E :_/ THRIPIDAE : 1. Aptinothrips rufus (Gmelin); 2. Odonto_ thrips ulicis (Haliday); 3, Limothrips cerealïum (Halidayl; 4, Heliothrips haemor.. rhoidalis (Souché); 5. Taeniothrips vulgat.. issimus(Haliday); 6, Taeniothrips atratus Haliday; 7, Thrips tabaci (Lindemann 8. Kakothrips robustus (Uzel) PHLOEOTHRIPIDAE: 1, Haplothrips distinguendus (Uel). The digestive system presents some peculiarities and in order to homologies the parts in the three families of thrips, with the typical digestive system of other insects, certain new nomenclature has been introduced where considered necessary, So far only four rectal glands were known to occur in thrips and I also found usually four in most species; but in Melanthrip fuscus, five rectal glands were found for the first time in Thysanoptera. The salivary glands also show difference of form and attachment, and in the course of anterior ducts, The female reproductive organs are more uniform except the difference in the form of receptaculum seminis; but the male reproductive organs show sometimes great dissimilarity. In Odonto_ thrips ulicis, a third kind of unpaired gland is found and in Taeniothrips atratus, the two testes are con_I netted by a commissure. These structures are not found in other species of thrips examined, Besides other minute details of form, and internal structures or their abnormalities are noted and described. The work was done in the Department of Agricultural Zoology, University of Edinburgh, under the super- vision of Dr 0.B. Williams. I am greatly indebted to him for suggesting this work to me and for placing at my disposal, all his collections and literature on Thysanoptera without which the present paper could not have been written. I am also grateful to Dr G.D. Morison for identifying a few species of thrips for me, and for sending me a specimen of the male of Aptinothrips rufus var stylifera.

During the season of 1929, studies were conducted with barley under field conditions to determine the relation between uniformity of spacing seed and development and yield of the crop. Information on this relation under American conditions was specially desired because of the observations of Engledow and his associates that yields of wheat fields in England were greatly influenced by the regularity of spacing seed. Two methods of planting were adopted in this study. In one, seed was planted in such manner that each foot of row received kernels evenly spaced and equivalent in number to a seeding rate of 10 pecks per acre, this being termed the uniform method. In the second, or variable, method, the average rate of seeding was 10 pecks per acre, but consecutive sections of the row were planted at different rates, equivalent to 6, 9, 11, and 14 pecks of seed to the acre, and a random distribution of the four rates was provided. Three rows of each method of seeding alternated throughout the test field, and observations were confined to the center rows to eliminate competition between unlike methods of seeding. A total of 140 foot sections of row were harvested from each of the uniform and variable methods of planting, and a detailed comparison was made of plant development and yield. Yields of grain and straw increased with the seeding rate when the component rates of the variable method were considered. However, the increase in yield was far from proportional to population density, because of the reduced development for individual plants at the closer spacings. The data indicate that the barley plant has considerable ability to modify its development in response to the soil resources available. The average yield of grain from the variable method of seeding was slightly greater than for the uniform method. No reduction in average straw yields resulted from irregularity of stand. Correlation coefficients between yield of grain for each foot section and the average rate of seeding of surrounding sections indicated that thickly populated areas draw on the soil resources of neighboring sparsely populated areas. The balance of the adjustment necessary for normal yields was brought about by increased development of individual plants in thin stands. Root studies indicated that root systems of this crop were not confined to the vertical zone occupied by the aerial portions, and that top growth of individual plants was correlated with root development. The conclusion is drawn that crops, such as oats, wheat, and rye, which are reported to develop more extensive root systems than barley, are probably even more capable of completely utilizing the soil resources in spite of considerable irregularity of stand. The variability of the soil was found to be a far more important factor in determining yields of units of the planted row than population density. Mean values of individual plant characters were not appreciably changed by the irregularity of spacing seed, nor was the reliability of the mean values significantly affected. Because of soil variation, a comparatively large number of samples of the crop will be required to represent fairly conditions in the field being examined. American grain drills, when functioning normally, may be assumed to distribute seed of small grains satisfactorily so far as total yield of crop is concerned. The factor of regularity in spacing seed may be largely ignored in conducting rate-of-seeding tests, even though the variation in seeding rate varies as much as 40% from the mean in consecutive sections of the row.

1. Because of slight variation in size, seed wheat for rod rows can be as well measured as weighed. A porcelain crucible, 16-cc capacity, holds about 11 grams of seed which, planted in rows 12 inches by 17.5 feet, equals a rate of 1 bushel per acre. 2. Slight differences in rates result whether seed be counted, weighed, or measured. Counting seed for large scale operations becomes too laborious and, even if counted, variation in germination may occur. 3. Oats vary in size more than wheat and the preferable method of determining the amount of seed has been by weighing for each row. The present paper is a study of methods and a comparison of results when seed oats axe counted, weighed, or measured. 4. In a comparison of weights of measured fine, medium, and coarse oats, the average weights respectively were found to be 13.1, 13.2, and 12.6 grams per measure (porcelain crucible 26- to 27-cc capacity). These weights are equivalent to about 2.4 bushels per acre, which is near the standard rate of seeding (10 pecks). Should a heavier rate be desirable a slightly larger crucible could be substituted. 5. Counts of these measured fine, medium, and coarse oats showed the average number per measure to be, respectively, 754, 584, and 516 seeds per measure. For oats as fine as 754 per measure, a smaller measure could be used, but the tests reported herein show little need of this substitution. 6. Similar counts on seeds of 10 varieties of spring oats showed only an allowable variation within a variety or even between the varieties. The extreme range in all was 468 to 734 seeds, but within a variety no range above 102 was found. The averages varied from 520 in Fulghum to 684 per measure in the Iogren variety. 7. In a test of rate of seeding of the fine, medium, and coarse seeded oats with from 100 to 700 seeds per row, the results showed that rates of 400 or more seeds per rod row gave the better yields. The number of heads per row was closely related to the number of grams per row, but neither one apparently was so closely correlated with the number of seeds used. 8. Results with counted (400), weighed (11 grams), and measured (26 to 27 cc) seeds of Fulghum oats showed a slight-difference in favor of the measured oats which indicates perhaps that a slightly heavier rate than with the counts and weights used is desirable for this variety. In another test this difference was not found. 9. With 10 varieties, Fulghum included, no difference of note existed in number of heads per row or yield in grams per row as between methods of weighing or measuring the seed, except with the Elite variety, in which the measuring method gave the poorer results. 10. The conclusion can safely be drawn that for the varieties tested the seed may as well be measured as weighed. This being carefully done will lighten the work of nursery planting.