Photosynthetic rates of detached, mature tea leaves from four different sources were determined in excess CO2 and light of 4, 10, 16 and 32 klux intensities from a tungsten-filament lamp. Temperature was maintained at 25°C. The assimilation rates were significantly different for the four sources both in weak and in strong light. Neither thickness of the leaf lamina nor chlorophyll concentration could explain the cause of this difference.

The effect of shade adaptation on the subsequent rate of assimilation was examined in one of the four sources of leaf. Shade-adapted leaves had significantly higher rates of photosynthesis at the weakest light intensity of 4 klux and lower rates in 16 and 32 klux intensities than the corresponding sun leaves.

The chemical composition of plants depends on many things, the species, the type of soil, the climate, the manuring, and it also changes during the growing season as different results can be obtained from samples of the same plant taken at different times. For plant analysis to be used in assessing the nutrient status and manurial requirements of crops there is need for knowledge not only about the above factors which can affect the chemical composition of crops but also about others that are less obvious, such as ion interactions. Ions can interact in two ways called antagonism and synergism; antagonism means that the uptake of one ion decreases the uptake of another ion and synergism that uptake of one increases the uptake of another.

The ratios of S cations (Na + K + Ca + Mg in m-equiv./100g.):2 anions (N + P + Cl + S in mequiv./ lOO g.), R values, in over 100 samples of Italian rye-grass grown in the field ranged from 0-33 to 0-92. Italian rye-grass, grown in the greenhouse at 11 levels of a nutrient mixture, had R values ranging from 0-58 to 1-36.

Natural infection by Verticillium albo-atrum occurred in two experiments, one comparing test crosses of inbred parents, the other a complete set of crosses between non-inbred parents. Although the uncontrolled variation was rather large, significant differences between progenies were detected in both cases. The differences were mainly accounted for by differences in general combining ability among the parents but not entirely so in the second experiment.

1. After synchronization of oestrus by treatment with progesterone before tupping small groups of ewes were slaughtered at approximately monthly intervals from 5 weeks post-conception to around 3 months post-weaning on two widely differing Scottish hill farms. A few barren ewes were also slaughtered.

2. Ash analysis of the 3rd, 4th and 5th cervical vertebrae of the breeding ewes indicated that there was a striking similarity between the flocks in the mean percentage ash values of these bones and also in the decline in these values which occurred between early gestation and 12 weeks after lambing.

In East Anglia Piesma quadratum is rare on wild beet and absent from sugar beet; it lives on wild plants and is confined to the coast. Larvae of P. quadratum which hatched from eggs laid on sugar beet in the laboratory died in an early instar, but older larvae and adults survived on the plants. There is little prospect that crinkle disease will become established in England.

The ratios of sum of the cations: sum of the anions (R) of sixty-two agricultural and horticultural crops and pasture herbs were measured or calculated and found to be negatively correlated with % N in the plants. This suggests that the proposal that Italian rye-grass has a mechanism regulating the proportion of cations to anions taken up may also apply to other plant species. Dicotyledons had greater B values than monocotyledons at the same N level, but this is probably not because their roots have greater cation exchange capacity.

1. Groundnut meal and herring meal have been compared as protein sources for ruminants.

2. Herring meal caused less extensive formation of ammonia in the rumen than did groundnut meal.

3. Nitrogen-balance experiments showed that herring meal fed to lactating goats was used more efficiently than groundnut meal fed under the same dietary conditions.

4. Herring meal was superior to groundnut meal for milk production in dairy cows.

1. Groundnut meals subjected to different degrees of heat treatment during manufacture were fed to lactating goats on nitrogen-balance experiment. The ‘toasted’ groundnut meal was more effective than undenatured or air-dried meals in promoting nitrogen retention.

2. The heat treatment of the groundnut meals did not influence the digestibility of the protein.

3. The groundnut meals were typed by determining their salt-peptizability giving values ranging from 44% for the ‘toasted’ meal to 80% for the air-dried meal.

1. Floret samples of S321 perennial rye-grass (Lolium perenne L.), S215 meadow fescue (Festuca pratensis L.) and S352 timothy (Phleum pratense L.) were taken at 3-day intervals from inflorescence emergence to seed harvest. These were analysed for total chlorophyll content, chlorophyll a: chlorophyll b ratio and total anthocyanin content.

2. All varieties showed qualitatively similar patterns of total chlorophyll content. At emergence chlorophyll first increased on exposure to light and then fell as anther formation progressed. After fertilization a rapid increase in floret chlorophyll content coincided with early seed formation due to pigmentation of the expanding seed epidermis. Polymerization of carbohydrates to form endosperm starch resulting in increasing dry-matter content caused a concomitant fall in total chlorophyll when assessed on this basis. The final stages of seed maturation were accompanied by a further gradual decline to a very low level.

1. Six diets in which the percentage of hay varied from 0 to 100% and the percentage of flaked maize varied conversely from 100 to 0% were each given to three sheep and three steers in a series of 72 calorimetric experiments. In addition the fasting metabolism of each animal was determined on two occasions.

2. The loss of energy in the faeces increased linearly with the percentage of flaked maize in the diet, but the loss of N in the faeces did not, the loss being proportionately smaller for diets containing more than 60 % maize.

Thirty-two ewes (of which 22 were P.M.S.- treated) were individually mated, each one eitherto two different rams or to four different rams successively, at predetermined intervals of time during a single oestrus period. The onset of heat was determined by a raddled vasectomized ram with free access to the ewe flock. Since each ram used was of a different breed the genotypes of the resulting lambs denoted which of the matings on each ewe had been effective.

The nutritive value of a sample of artificially dried lucerne was determined calorimetrically in twelve experiments with three sheep.

1. A feeding trial involving sixty-four individually fed pigs was carried out to assess the effect of reducing the protein content of the diet at different live weights. The effect was examined at two planes of protein intake, 19 % falling to 14 % in the finishing stages, and 16 % falling to 12 %.

2. High protein levels improved growth rate and food conversion efficiency during the growing phase, and also improved carcass quality in terms of the lean content of the carcass, eye muscle area and length.

An objective appraisal system for intact lamb and mutton carcasses utilizing a fleshing index to relate carcass weight and length is presented. Gross fleshing index is defined as the number of pounds by which any carcass is heavier or lighter than the average carcass of its particular length. Penalty for overfatness is made when necessary by an estimation technique involving measurement of fat status at the level of the first lumbar vertebra on the intact carcass with the aid of a steel probe. The net fleshing index, a simple numerical expression of carcass fleshing, is arrived at by deducting the penalty for overfatness (when necessary) from the gross fleshing index. The greater the net fleshing index the greater the relative merit of the carcass.

1. The value of ‘worm-free’ sheep in the assessment of pasture is illustrated by an experiment in which the effect of internal parasites could only be distinguished by the use of ‘worm-free’ controls.

2. The effect of augmenting the initial pasture infestation (with nematodes parasitic in the sheep) was slight.

3. In an experiment with ewes and lambs at three lambing percentages and over a range of stocking rates: