1. An in vitro method is described whereby it is possible to obtain the digestibility coefficient of silage cellulose. The apparatus and techniques used are described in detail and the reproducibility of the results obtainable is stressed.

2. The results so obtained on twenty-seven samples of silage of diverse nature, with regard to composition and method of production, show a reasonable degree of correlation with the corresponding figures for the digestibility coefficients of crude fibre obtained by feeding trial.

1. Laboratory incubation studies with topsoil samples of the Kikuyu red loam coffee soil have shown that active nitrification of the natural soil nitrogen stops at a soil moisture level just below the permanent wilting percentage. Ammonification of natural nitrogen in this soil does not cease at this moisture level and ammonia nitrogen accumulates substantially, although the values found at the end of the 32-day incubation period, and the rate of ammonification are significantly lower as the moisture level is decreased from ⅚ to of the permanent wilting percentage.

A range of populations of cereals and herbage grasses, mainly of Lolium, Phieum and Triticum, have been tested in the greenhouse for response to lowtemperature vernalization. Leaf number before heading was used as the measure of reproductive development.

A close correlation was found between the climatic or agronomic origin of each population and its response to low temperature. In the cereals, response to low temperature was found in one ecological group only, namely, the winter wheats from western Europe. In Lolium the duration of the life cycle is closely related to the response to vernalization. The annual strains, such as Westernwolths or Wimmera ryegrasses, head rapidly with little or no response, while most of the perennial strains have an obligatory requirement for low temperature. In Phieum none of the populations tested exhibits any marked response to, or requirement for, low temperature, but the rapidity of heading, as measured by leaf number, varies from strain to strain and shows a high correlation with persistency. Most of the weed species tested are short-lived annuals and show little or no response to low temperature.

For each population, the local climate and farming system determine the optimum life cycle, and response to low temperature forms one important mechanism whereby such a life cycle can be attained.

The value of these methods for varietal classification and identification was assessed by comparing the behaviour of the same material in two or more seasons or under two or more kinds of equipment. The type of lighting used to provide long-day or continuous illumination, and the date of sowing, have a differential effect only in Phalaris and Phleum. In the other material, while variations in sowing date produce slight differences in the leaf number, the interaction between strain and sowing date is small, and good discrimination between population samples is possible. It is important to keep the greenhouse temperature between 50 and 70° F. to avoid natural vernalization or devernalization of material. The use of probit diagrams for comparing truncated distributions is discussed.

It is suggested that the methods can also be used to assess the genetic variation within populations. In the present results, the effect of the breeding system on the storage of variation is well shown. In self-fertilizing species, little or no variation is carried within lines, or, in the one case tested, between stocks of the same variety; it can, however, be carried between lines in a local population. In outbreeding species, each population carries considerable variation, both as genetic differences between individuals and in the heterozygous condition within individuals.

1. A diluter for semen containing egg yolk, glycine, sodium citrate, fructose and glycerol is described.

2. 2005 inseminations gave an over-all conception rate of 65·7% (90–120 days non-returns) after periods of storage varying from 24 to 196 hr.

3. 401 inseminations after storage for 24–48 hr. gave a conception rate of 75·3%, compared with a conception rate of 60·0% on 398 inseminations after 96–144 hr. storage, using semen from the samecollections.

4. A possible use for modified glycine diluters for nominated service at A.I. centres is suggested.

1. Four replicated experiments were made to determine the rate of passage of meal through the alimentary tract of pigs on different feeding treatments. In each experiment stained meal was used and the results were expressed by means of excretion curves. From these, mean retention times (R values) were calculated. All the curves were of a similar sigmoid shape.

2. A significant inverse relationship was found between the mean retention time and the total weight (meal plus water) of the ration. This relationship was found when (a) the weight of meal was constant and the weight of water was varied, (b) the weight of water was constant and the weight of meal was varied, and (c) the total combined weight of meal and water (at the same ratio) was varied.

3. The digestibility of the dry matter and crudec protein in Exps. 1–3 was not altered greatly as a result of the different feeding treatments.

4. In Exp. 4, similar rates of passage were found in pigs fed on the two rations of widely different digestibilities.

5. The dry-matter content of the faeces of the pigs was remarkably constant over a wide range of water and food intakes when using the same meal.

1. The live-weight gain of lambs initially infected at five different levels was compared with that of similar but worm-free animals, under conditions of set-stocking at a high rate per acre.

2. Over a period of 9 months the worm-free controls gained 67·7% more weight than the total infected group, but the live-weight gains of the five levels did not appear to be related to their original infection or to their egg counts.

3. Although a few nematode eggs were detected in the faeces of some control lambs, reinfection was negligible under the conditions of this experiment.

4. It was concluded that a marked depression of productivity may be associated with an egg count as low as 114 e.p.g. in sheep 4–7 months of age.

1. The rate of loss of weight has been determined for eggs from aged hens and from pullets by methods which used both an incubator at 102° F. and a desiccator at room temperature.

2. For both lots of eggs the weight loss per unit area of shell was about three times greater in the incubator than in the desiccator.

3. For the same method the eggs from the aged hens lost one and a half times as much weight per unit area as the eggs from pullets.

The possibility was examined of supplying vitamin A to chickens from the first days of life as carotene in green plants. Growth experiments were carried out with chickens till the age of 8 weeks. Different kinds of forage (horse-beans, Berseem clover, green oats, sweet potato leaves, cow-peas, corn-leaves) were given in quantities calculated to supply 300 μg. carotene per 100 g. feed; control groups received fish-liver oil, given at the level of 500 i.u. per 100 g. feed. Weight gains and extent of vitamin A storage in liver served as an indication of the utilization of carotene from different sources. The utilization of carotene from all the plants examined was sufficient to support normal growth, only in the groups receiving clover was growth found to be somewhat slower. Remarkable differences were found in the extent of liver storage, and that was taken as an indication of differences in activity of the carotene from the different sources.

Attempts to determine the reasons for these differences in liver storage capacity of the carotene from the various plants did not reveal the presence of any plant components enhancing or depressing vitamin A storage.

Similarly, no correlation could be found between digestibility coefficients of carotene in the different plants and liver vitamin A storage. This correlation seemed likely in sweet potato leaves only, the rather low digestibility coefficient found in these leaves may account, at least partially, for the low activity of this plant.

The stereoisomeric composition of the β-carotene of the different plants and the xanthophyll/carotene ratio are very similar in all plants tested and cannot account for differences in carotene activity of the plants studied.

The results of this work show that it is possible to satisfy the requirements of chicks for vitamin A from the first days of life by supplying certain forage plants. In practice, because of the variability of the carotene content in such plants, care has to be taken when estimating the amounts to be given. Green plants should be given to chickens freely or at least in liberal amounts.

1. The results of five experiments, comparing the wool production of worm free and infected sheep, are described.

2. Worm-free sheep produced (a) 12·0–38·8% higher total fleece weights and (b) 17·2–43·2% more clean, dry wool per unit area than infected sheep. None of the infestations was higher than occurs naturally in the field, but the greatest effects were associated with a low level of nutrition.

3. It is suggested that the precise effect of worm infestation on wool production will depend upon the age of the host when first infected, the size of the infestation and the rate of wool growth at the time when the infestation is at maximum.

1. Lucerne seed samples of known harvest history were treated by dry heat at various temperatures and durations; their germination capacity, emergence and establishment were tested by laboratory, greenhouse and field establishment tests on heavy Boil during 1952–6 at Cambridge.

2. A successful and safe heat treatment was 42° C. for 5 days, increasing the germination by as much as 44% up to about 90% at the cost of hard seed.

3. The establishment obtained on heavy soil from treated seed samples, although varying from season to season, was significantly higher (P > 0·001) at all seed rates than that obtained from untreated control samples.

4. Significant differences were obtained in germination capacity and establishment between samples harvested at different conditions. High moisture content of seed and high percentage of dark brown seeds was associated with late harvest. Brown seeds had a significantly lower germination capacity than yellow seeds. Only samples with a high initial moisture and high percentage of brown seeds showed a substantial decrease in germination capacity during the storage period of 3 years.

5. Although the mean number of plants established is significantly higher for higher seed rates the mean percentage of plants established decreases significantly with higher seed rates and the greatest wastage of seeds occurred at the high seed rate of 15 lb; per acre.

6. The viability of seed and speed of germination and of emergence were the most important factors in determining the successful establishment of a crop on heavy soil.

7. Hard seed is viable and could germinate and produce seedlings by the end of the season, but only a very small percentage of it could normally be established under field conditions. With untreated seed no significant correlations were established between laboratory germination and field establishment or between laboratory germination and greenhouse emergence, yet there were highly significant correlations in these cases for treated seed. With increased duration of laboratory germination test, corresponding to a decrease in the proportion of hard seed, values of r increased. Correlations between field establishment at three seed rates and greenhouse emergence were significant in the case of both untreated and treated seeds.

8. When the hard seeds were added to germination or establishment the relationships between the results of these tests were very close and highly significant correlations were established for both lots of seed, untreated and treated. The high proportion of hard seeds was the main limiting factor preventing a close relation between tests for untreated seed.

1. The reflex ejaculation responses of cocks to lumbar massage have been examined, and some basic reactions described. A list of the crude fluid components obtained by the massage technique of semen collection is given.

2. From these observations, and a chemical test on the contents of the hen's vagina after natural and artificial insemination, it was deduced that the normal ejaculate of the cock is composed mainly of contents from the vasa deferentia, with some secretions from the mucosal glands of the vascular bodies and lymph folds. The blood plasma transudate sometimes expelled into the semen is obtained as a result of compression of the terminal organs during the collection procedure.

3. Points emerging from the observations on ejaculation, and the search for the normal constituents of semen are discussed.

Equipment for milking sows by machine and the technique employed are described.

The writer wishes to express thanks to Mr H. S. Hall, of the National Institute for Research in Dairying, for assistance in the selection of suitable teat cups, and to the Avon India Rubber Co. Ltd, for kindly supplying the liner tubing.

1. The diploid species Secale cereale (2n= 14) is self-incompatible, Aegilops longissima (2n = 14) and A. caudata (2n = 14) are self-compatible. A. longissitna is usually self-pollinated and A. caudata is usually out-pollinated.

2. Meiotic behaviour, constancy of chromosome number and seed fertility have been examined in the three octoploid amphidiploids derived from crosses of Triticum vulgare variety Holdfast (2n = 42) with S. cereale A. longissima and A. caudata respectively.

3. All the amphidiploids had cells in which some chromosomes were unpaired at first metaphase of meiosis. This meiotic irregularity is not, therefore, related to the breeding system of the diploid parent.

4. The fertility of the amphidiploids was not related to their meiotic regularity.

5. The least fertile amphidiploid was derived from the self-incompatible diploid S. cereale. The most fertile amphidiploid was derived from the selfcompatible, self-pollinating diploid, A. longissima.

6. It is suggested that the infertility of the wheatrye amphidiploid may result from interactions between genotypes adapted to different breeding systems, rather than from the homozygosity in the amphidiploid of deleterious recessive genes derived from the outbreeding rye parent.

7. The demonstration of the independence of meiotic regularity and fertility will complicate selection work on wheat-rye amphidiploid material.

1. A series of experiments designed to compare the effects on the succeeding wheat crop of five different methods of treating the aftermath of a Broad Red Clover ley is described and the results discussed.

2. There was little consistent difference in the effects of using the second crop for hay, for grazing or for green manure by ploughing it in. Bastard fallowing immediately after the first hay crop and taking the second crop for seed both showed large seasonal fluctuations in their effects, but there was insufficient evidence to show if these were due to seed-bed differences.

3. In no season was taking the second crop for hay outyielded by any other treatment.