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With 3 figures in the text) Brown (1906) has described the results of an early investigation on the ability of mature, isolated cereal embryos to utilize organic forms of nitrogen. He reported that ammonium sulphate, aspartic acid, glutamic acid, potassium nitrate and asparagine, at concentrations supplying equivalent quantities of nitrogen, showed progressive increases in their capacity to increase the dry weight and nitrogen content of barley embryos cultured for a period of one week. Out of these nitrogen sources only asparagine produced an increase in the growth in length of the roots, while all, with the possible exception of ammonium sulphate, produced an increase in the length attained by the shoot system. Phenylalanine, tyrosine and leucine were distinctly inhibitory to growth. So far as the author is aware, there have been no other recent reports of comparable studies on the ability of isolated cereal embryos to utilize organic forms of nitrogen for growth.The purpose of the present investigation was to assess the value of amino acids as sources of nitrogen for the growth of mature oat embryos isolated from their endosperm. Particular attention has been given to interactions occurring between amino acids in their effects on the growth of the embryos. A note on some of the experiments described has appeared elsewhere (Harris, i9S3a). METHODS Method of establishing culturesVictory oats of the 1949 harvest, kindly supplied by Messrs, Webb, Stourbridge, were used throughout the experiments. Dehulled grains were surface-sterilized by shaking in 0,1 per cent mercuric chloride solution for 20 minutes. They were then rinsed four times in sterile distilled water and placed in sterile petri dishes each containing a piece of filter paper moistened with 5 ml, distilled water. The grains were germinated in the dark at a temperature of 25 ± 1° C, for 16 hours. The embryos were then excised under aseptic conditions in a transfer room. A sharp-pointed scalpel was used to make an incision in the outer tissues of the grains along either side of the scutellum. The embryo could then be levered away from the endosperm without injuring its tissues.Each isolated embryo was transferred to a separate culture vessel containing 50 ml, of liquid culture medium. The culture vessel employed (Eig. i) consisted of a Pyrex glass tube fitting into the mouth of a 100 ml. Pyrex wide-necked conical flask. The tube was held in position at the mouth of the flask by a collar of non-absorbent cotton wool surrounded by a piece of surgical gauze, A plug of cotton wool, also protected by a piece of gauze, was fitted into the upper end of the tube. The embryo was supported at the surface of the culture medium on a piece of gauze held in position across the lower end of the

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Treatment of tomato plants with (2-chloroethyl)trimethylammonium chloride (CCC) reduced their growth in height and d. wt and increased the number of flowers formed in the first inflorescence. In plants grown at a high temperature with low light, application of CCC reduced the incidence of flower abortion in the first inflorescence. Effects of a-cyclopropyl-a-(4-methoxyphenyl)-a-(pyrimidin-5-yl)methanol (ancymidol) were similar to those of CCC while a third growth retardant, A'-dimethylaminosuccinamic acid (B-9), was effective in reducing growth in height but was without apparent effect on flower number or flower abortion.An interaction occurred between CCC and GA 3 such that effects of CCC on growth and flowering were reduced when GA 3 was also applied. Yields of diffusible gibberellin-like substances from the shoot tips were markedly reduced by treating plants with CCC but were apparently not affected by treating plants with B-9. It is suggested that effects of CCC on flowering in tomato are mediated, in part at least, through changes in levels of endogenous gibberellins.