Ewes of three breeds, Devon Longwool, Kerry Hill and Welsh Mountain were injected with different levels of Pregnant Mare Serum Gonadotrophin (PMSG) for 3 consecutive years. Within the levels of PMSG examined (0–1500 i.u.) the highest mean litter size was obtained at 1000 i.u. for the Devon Longwool (2·10) and the Welsh Mountain (2·33), and at 1500 i.u. for the Kerry Hill (2·41). This represented a response of 0·66, 1·28 and 0·56 extra lambs born for the Devon Longwool, Welsh Mountain and Kerry Hill breeds, as untreated ewes of these breeds produced 1·44, 1·05 and 1·85 lambs/litter. The lambing percentage attained was, however, lower than the response in litter size indicated, due to the incidence of barren ewes and of lamb mortality.

Though the Devon ewes were heavier than the Kerry's, twin lambs out of the latter were bigger than twins from the Devon's. The relationships of body weight and of natural fertility to optimum dosage of PMSG are considered. There is discussion of the maximum litter size and minimum birth weight compatible with the production of viable lambs.

The amount of dry matter produced and N taken up by seven grass species and varieties grown in a glasshouse were compared with perennial ryegrass (S. 23) and Italian ryegrass (S. 22) at different day-lengths and light intensities.

The ryegrasses Westerwolds, Italian (S. 22) and Perennial (S. 321) yielded more than S. 23. At the smallest light intensities, Westerwolds, Italian (S. 22) and Perennial (S. 24) (S. 321) ryegrasses and Meadow fescue (S. 215) took up more N than S. 23. Westerwolds and Perennial (S. 24) (S. 321) ryegrasses should be useful alternatives to the S. 23 or S. 22 strains as test crops in nutrient experiments in the glasshouse, especially when grown in the dim light during winter.

Two methods have been used previously to resolve the ‘mineral’ and ‘organic’ fractions of the cation exchange capacities of soils. Williams (1932) and Hallsworth & Wilkinson (1958) used multiple regression analysis to relate cation exchange capacity (CEC) in several soils to percentage organic matter (OM) and percentage clay, and thence to calculate the average values of the CECs of OM and clay. For individual soils, Davies & Davies (1965) and Clark & Nichol (1968) measured the CEC before and after oxidizing the OM with hydrogen peroxide.