1. Twenty-one varieties of pasture grasses, including ten bred varieties, were grown on fertile soil for 3 years. Figures are presented of the rate of production of herbage cut every 3or4 weeks. Plots were cut in staggered sequence to permit growth intervals to overlap and to allow frequent assessments of the rate of production.

During the interval from seed set to advanced shedding in a crop of S24 perennial ryegrass, a study was made of: seed drying, the increase in germinating capacity and weight of seed, and the shedding of ilorets. The seed in early-emerged heads dried more rapidly than that in later heads, and the seed In the upper parts of each spike was drier than in the lower parts. Seeds in early heads attained maximum germination values about 18 days after anthesis. The maximum value was lower in later heads and was not reached until approximately 26 days. Seed in early heads was 67'^,, heavier than that iti late heads and the basal florets in each spikelet contained heavier seed than more distal ones. The maximum weight of individual seeds was reached al about ihe same time in early-emerged and intermediate heads, at about 22 to 26 days after anthesis. Seed in late heads continued to inerease during the whole interval studied. Shedding began before seed reached maximum dry weight and continued at a constant rate. The combination of these processes led to the maximum yield of seed, of lOO' *,, germination, being obtainable over a period between 20 and 26 days after anthesis. Criteria are given which would permit this stage to be recognized.

1. Swards of perennial ryegrass (S 24) were grown under conditions of high fertility and were cut at intervals of (a) 3 weeks, (b) 6 weeks, (c) 3 weeks changing to 6 weeks at later points in the growing season.2. The rate of herbage production (kg D.m./ha/day) was higher throughout the season (April to November) under the longer cutting interval. Plots which were changed from 3- to 6-weekly cutting intervals subsequently showed the same rate of production as those cut every 6 weeks throughout.Inflorescences emerged from a higher proportion of tillers after long growth periods; this could explain the higher rates of production up to July.

In a seed crop of S24 perennial ryegrass the processes of anther exseriion and seed formation were measured in inflorescences which emerged early, intermediate and late. The peaks of anther exsertion in the three groups were simultaneous, although the proportion of heads showing anthers was lower in late heads.Two-thirds of all Horets set seed, but the proportion was lower in late heads than in the earlier groups. There was a slight fall in floret fertility in the upper spikelets, compared with those in the middle and at the base of the spike, and a marked reduction in fertility in the outer florets of each spikelet.Factors likely to affect the efficiency of the pollination and fertilization process are discussed.

It has been found that the rate of herbage production from perennial grass swards, cut at a stage suitable for grazing, is lower in midsummer Ihan in late spring. This occurs even with an abundant supply of water and fertilizer. The growth rate of green material was measured in swards differing in leaf area and light interception, Results did not suggest that higher growth rates could be obtained by attention to this relationship. Examination of the tiller population of grass swards showed that, in summer, herbage yields from cocksfoot and timothy were correlated with the average tiller size. This was not so in either of 2 varieties of perennial ryegrass. During May, June and July there were changes in the erectness of the swards as measured by the proportion of the crop which could be harvested with a mowing machine. This proportion was maximal when the highest rates of production of herbage were recorded.The importance is discussed of the change from a phase when mature tillers are forming inflorescences to one when herbage is derived from young, vegetative tillers formed in the same summer.