A study has been made of some of the nitrogen fractions of the pegasse soils of British Guiana in virgin and exhausted conditions, that is, before and after cropping.

1. Preliminary field experiments on the virgin and exhausted soils adduced strong evidence in support of the complaints made by farmers that the productivity in yields of the pegasse soils after continuous cropping for a comparatively short period is considerably impaired.

2. The virgin soil showed an appreciable amount of nitrate nitrogen, while the exhausted sample indicated no nitrate. The latter soil, on the other hand, contained a higher amount of ammonia nitrogen measured by KCl extraction than the former soil.

3. Nitrification studies with added ammonium salts indicated that under optimum conditions the nitrifying power of the exhausted soil was extremely low. Additions of sodium nitrate indicated that the nitrate was partially reduced to ammonia by the worn-out pegasse soil. The virgin pegasse, on the other hand, showed an appreciable rate of nitrification.

1. A feeding trial is described including four groups of cattle fed on silage only, two mixtures of silage and roots, and roots, straw, hay and oats.

2. The live-weight gains made are recorded together with the rate of dry-matter intake.

3. The efficiency of the dry matter of the diets was calculated.

4. Silage fed alone produced a significantly greater rate of fattening than the other three diets.

5. Cattle receiving roots in the morning and silage at night consumed 10·78% more dry matter and made greater live-weight gains than cattle fed on silage in the morning and roots at night.

6. Calculation of the starch values of the roots and silage showed that these are higher when fed together than when silage is fed alone or when roots are fed with straw, hay and oats.

7. An experiment is described designed to determine the effect of the dry-matter percentage of the diet on dry-matter intake in ruminants and of sudden changes in dry-matter content on digestibility.

8. Sheep receiving 19·46% dry-matter silage consumed 16·7% more dry matter and 19·8% more starch equivalent than sheep eating 15·85% dry-matter silage.

9. When the dry-matter percentage of the silage fell from 19·46 to 15·77 the digestibility of the dry matter fell by over 10%.

10. The starch equivalent of the silage when fed alone was determined from the results of a digestibility trial and according to the performance of the cattle in the feeding trial. The values found were 65·88 and 66·15% respectively.

11. The losses suffered in silage-making in twentyfive silos are recorded and discussed. The loss of dry matter and crude protein both average approximately 40% of that ensiled. The need for finding methods of reducing these losses is again stressed.

1. Studies were made during the 1951 and 1952 seasons of the oxalate contents of the leaves of mangolds, sugar mangolds and fodder sugar beet.

2. In all varieties greater concentrations of total oxalates were found during the summer months, the amounts diminishing gradually as the season advanced. Up to 12% was found in the dry-matter of mangold leaves and 9% in fodder sugar-beet leaves in July, these levels falling to 3% by mid-winter. There is some evidence that these changes are due in part to loss of outer leaves.

3. Roughly one-third of the oxalates are present in water-soluble form. The addition of 1 part of chalk to 1000 parts of leaves, as has been generally recommended, is theoretically sufficient to render unavailable the soluble oxalates present during winter, but insufficient for leaves fed earlier hi the season.

4. A number of observations showed small reductions in the soluble oxalate contents of the leaves due to wilting, but there were exceptions to this, and these appear to be related to sampling periods rather than to varieties.

5. Insoluble oxalates appear to be unaffected by wilting and may show apparent increases in amount due to respiration losses of labile leaf constituents. The insoluble/soluble oxalate ratio is thus changed by wilting.

6. It is suggested that the undesirable effects sometimes resulting from the feeding of beet leaves to livestock may not be due to oxalates, but that other factors present, which are labile during wilting, may be involved.

1. Experiments were carried out to test the effects of the three main mineral fertilizers on the secretion of nectar by apple, mustard and buckwheat. Factorial designs were used, and data on plant growth were collected in order to attempt to relate growth to nectar production. Apart from the apple trees the plants were cultivated in clean sand to which known quantities of pure minerals were added.

2. Apple. The mean quantity of sugar per flower was significantly increased by extra potash; phosphate also tended to increase it. At the higher level of potash, nitrogen had significantly increased the crop of apples the previous year; it decreased the nectar yield. Potash increased nectar yield most when its effect on the crop had been small, and vice versa.

3. Mustard. In this experiment the quantity of water supplied to the plants was varied as well as the fertilizers. On the last sampling occasion nectar was more frequently obtained from plants with the lower dose of nitrate than from those with the higher dose. At the high level of water, and with low nitrate, extra potash consistently increased the mean quantity of sugar per flower but with the high level of nitrate it consistently decreased it. The phosphate level had no significant or consistent influence on nectar yield.

Treatments increasing nectar production tended (a) to decrease stem weight and total number of flowers; (b) to retard flower production, probably as a consequence of relatively slower growth; (c) to increase petal length, and (d) to increase the proportion of plants with orange or red pigment in the withering leaves.

4. Buckwheat. Nectar was obtained significantly more frequently from those plants which had received extra nitrate and extra potash. It is suggested that the nitrate effect was due primarily to the senescent condition at the time of sampling of some of the plants with the lower dose, especially those which also had the high level of phosphate, and to the interactions of nitrate with phosphate and potash in respect to nectar production. Such explanations do not account for the effect of extra potash. Extra nitrate and potash always increased the stem weight and number of flower sprays; phosphate had little effect.

1. The1951 clover experiment. No significant effects on the mean yield of nectar were obtained, but the higher dose of phosphate significantly increased the frequency of zero samples during August, the main flowering and sampling period; so also did the higher dose of potash in the presence of high nitrate. In general those treatments which depressed nectar secretion resulted in a larger proportion of flowers opening before mid-August. Accelerated flower production appeared to result from more rapid growth during August.

2. The 1952 clover experiment. The treatment effects on quantity of sugar per floret were compared with those on final stem weight. Treatment effects on sugar/floret on particular sampling occasions were compared with the effects on relative ‘growth rate’ during the preceding period. Additional phosphate always resulted in greater and more rapid growth, but it only reduced the nectar yield in the presence of the highest level of potash. In the presence of low doses of potash nectar secretion was consistently poor. Additional potash did not increase the nectar yield if it resulted in greater or more rapid growth; if it did not affect size or growth rate it increased the nectar yield. Clonal differences in nectar production were greater than treatment ones.

3. The responses of the four species used in this series of experiments are compared. The results of other workers on the effects of fertilizer treatments on nectar production are discussed in relation to those reported here. If the balance between different fertilizers and their effects on growth are considered, as well as nectar yields, contradictions between the results of various workers can be explained. It is suggested that when potash tends to limit growth nectar secretion is likely to be consistently poor, but that when growth tends to be limited by nitrogen or phosphate a relative surplus of potash will promote good secretion.

Reference is made to work on the relation of the sugar supply in plants to nectar secretion and on the relation of fertilizers to the sugar supply. Tentative recommendations are made which require confirmation in field tests.

1. A series of grazing behaviour observations on 10 sets of lactating identical twins is described. Four fortnights distributed over the main lactation period were covered. In three of the fortnights, the observations were made on six 24 hr. periods, while in the remaining fortnight the cows were observed on all 14 days.

2. Anoutstanding feature of the grazing behaviour of dairy cattle is its variability, due to external and internal conditions.

3. Of the external factors, climate (in a temperate zone) is relatively unimportant.

4. The quantity and quality of the herbage offered are of importance in modifying the grazing behaviour of dairy cattle. Under adverse pasture conditions there is, in general, an increase of total working time (grazing + ruminating): grazing time increases with scarcity of herbage and with mixed quality, while ruminating time is prolonged by poor quality grass.

5. Ruminating time is strongly dependent on the quantity and quality of the ingested grass, but the relationship is, for various reasons, obscured in a field trial such as the present.

6. The adaptation of grazing habits to new conditions is very rapid.

7. Feed requirement for milk production is the most important internal factor determining variation in the length of grazing time.

8. Inheritance × environment interactions as a source of variations in grazing times are due to the following factors:

(a) Differences amongst twin sets in lactational persistency, which presumably cause parallel differences in feed requirements.

(b) Differences in the response of high and low producing twin sets to varying pasture conditions.

(c) Non-analysable idiosyncrasies common to the members of some twin sets.

9. Twin sets graze and ruminate at a characteristic rate.

1. The numbers of Streptococcus bovis in the rumen of a heifer and a steer, each having a permanent rumen fistula, were shown to remain relatively constant within the range 105 to 107 per ml. rumen liquid (strained rumen contents) over a period of more than 3 years.

2. The numbers of Strep. bovis were little affected by the change in diet from stall-feeding (oats, beans, hay and straw) to grass or vice versa.

3. There was a slight increase in the numbers of Strep. bovis following each meal when the animals were stall-fed, but no appreciable variation in numbers throughout the day when the animals were at grass.

4. Strep. bovis has also been isolated from the rumen of freshly slaughtered cattle and sheep from different parts of the country, from the rumen of goats and calves and from the faeces of cattle, goats and in small numbers associated with Strep. equinus from horse dung.

5. Strep. bovis was found in the contents of the omasum, large intestine and caecum of three cattle, but in the small intestine of only one of these animals. Very small numbers of Strep. bovis were detected in the abomasal contents of only four of twelve animals examined.

6. The characteristics of these strains of Strep. bovis have been described. The synthesis of an iodophilic polysaccharide by Strep. bovis has been demonstrated.

7. A possible role of Strep. bovis in the decomposition of starch and other carbohydrates in the rumen is discussed.

1. The development of the fleece and follicle population was studied in six Herdwick and two Herdwick × Swaledale sheep on their native farm in Cumberland. Six of these sheep survived the first 14 months of the experiment, and four were kept under observation for a further 12 months. Growth in body weight, body surface area, and area of tattooed squares was recorded and discussed.

2. Fibre type arrays (at the mid-side positions) were ‘Plateau’ in all but one of the pure Herdwick lambs, and ‘Saddle’ in the remaining three animals.

3. The earliest fibres of the array (halos and coarse super-sickles) were mostly ribbon-shaped in their pre-natal and early post-natal portions, below which they became cylindrical. These fibres were ‘birth coat kemps’ and were shed about 10 weeks after birth. At this time later-developed fibres (sickles and curly-tips) showed ‘crisis thinning’ but did not shed, whilst late curly tips and histerotrichs were not affected. These three groups gave rise to three corresponding groups of fibres in the adult fleece, namely kemps, hairs and fine fibres.

4. Two generations of kemp fibres were grown each year, ‘spring kemps’ commencing growth about April and shedding by July; and ‘autumn kemps’ commencing growth in July and forming ‘brush-roots’ in the autumn and early winter, although the majority remain in their follicles until the following spring.

5. The majority of the curly tip fibres of the birth coat grow into long hair fibres, which are of hetero-typical shape. In summer they are more or less coarse, and medullated, whilst in winter they become fine and lose their medulla; many cease growth during the middle of the winter period after producing a short length of fine fibre, and commence growth again in the spring. The late curly tip and histerotrichs fibres continue to grow as the fine undercoat fibres of the fleece, without any medullation.

6. A large proportion of both primary and secondary follicles shed their fibres during the winter months. When this proportion is sufficiently high this leads to a severe ‘winter break’ in the wool staple. The visible ‘break’ is the result of the combined effect of the winter fining of heterotype hairs and the shedding of some of all types. Fibres traversing the break were found to be either long heterotypes or long fine fibres.

7. The adult colour of any individual Herdwick sheep is the result of the interaction of several factors of which the main ones are: (1) later fibre types tend to be less pigmented than early types; (2) less vigorous growth of an individual fibre tends to reduce its pigmentation; (3) a more or less extensive acromelanic pigmentation; (4) the white areas may be affected by various degrees of speckling or roaning; (5) the kemp-like hairs of the face and legs are black at birth, and these are eventually shed and replaced by similar but unpigmented fibres.

8. Numerical data on the fibre and follicle population are presented. The mean proportion of the three main fibre types (all sheep, all seasons) was: coarse 18%, medium 25%, fine 59%. The mean adult follicle density was 1012 per sq.cm. and the mean adult S/P ratio was 3·37:1.

This paper, which forms part of a series of investigations on the potato crop, presents evidence obtained from experiments reported in the literature on the relation between seed rate and yield of maincrop potatoes. The available experiments are sufficient to indicate what is the average relationship between seed rate and yield, but are insufficient to demonstrate any clear differences between different parts of the country, soil types or even different varieties.

Using this average relationship, optimum seed rates are presented for a range of prices of seed and produce. These optimal rates are compared with estimates from surveys of the actual amounts planted by growers in different parts of the country.

Provided the optimum seed rate is attained the precise combination of seed size and spacing distance appears to be of minor importance; that is, a grower should aim to plant at the optimum seed rate regardless of seed size. There is, however, an upper limit of spacing between sets which should not be exceeded however large the seed may be.

The optimum rate of planting at 1952 prices of ‘A’ or ‘H’ certificate seed is estimated to be 16–17 cwt. in most of the main potato-growing areas of the country, though it may be a little higher where a grower has a market for once-grown seed. Surveys indicate, however, that the normal planting rate of certified seed is over a ton to the acre in these districts.

For a grower's own once-grown seed, on the other hand, for which the cost is not more than the price received for ware, the optimum seed rate is at least one ton per acre, whilst the average weight of seed actually planted is only about 17 cwt. per acre. It is estimated that the average loss per acre due to this failure to plant at the optimum seed rate amounts to 20–25s. per acre planted with certified seed and 10–15s. per acre for once-grown seed.

1. Follicular fluid was collected by aspiration from the ovaries of cows which had been treated with pregnant mare serum, and were killed 3–4 days after heat.

2. Various chemical determinations have been carried out with samples of follicular fluid which, amongst others, was found to contain 39–43 mg./ 100 ml. of glucose, between 13 and 95 mg./100 ml. of lactic acid, and 0·8–3·0 mg./100 ml. of ascorbic acid.

3. The effect of follicular fluid upon sperm fructolysis was examined; however, no effect other than that due to the glucose content of the follicular fluid, could be observed.