EMBRYOGENESIS IN FLOWERING PLANTS 295 



emulsions of (i) the ethyl ester of indoleacetic acid and (ii) naphthalene 

 acetic acid at a concentration of 1000 p. p.m., a concentration which is 

 effective in inducing the parthogenetic development of the kernels 

 (Britten, 1950). These were compared with ears in which normal 

 pollination had been effected, and with ears sprayed with a water-lano- 

 line emulsion (as control). In the course of several days no significant 

 changes took place in the carbohydrate content of the kernels used as 

 controls, whereas in both the hormone-treated and pollinated kernels 

 there were marked and qualitatively comparable changes, i.e. an 

 increase in the starch content from its initial low level and in reducing 

 sugar, and a decrease in sucrose. The cob was similarly affected in 

 respect of these changes, indicating that the hormone effect is not 

 restricted to the developing kernels. The pollination and the artificial 

 hormone treatments also resulted in some increase in the hexose 

 phosphates in the kernels, suggesting that the production of these 

 substances was greater than their utilisation, notwithstanding the fact 

 that the ovary was in an active state of growth. In this experiment, 

 Marre and Murneek have thus been able to show that there is a close 

 similarity between the action of the hormones, or growth-regulating 

 substances, naturally released by the act of fertilisation and those 

 which can be applied artificially. In observations of this kind we get a 

 glimpse of the complex system of biochemical factors and metabolic 

 changes involved in the development of the embryo and endosperm. 

 With the improvement of techniques there can be little doubt that very 

 substantial progress will be made along these lines. Indeed, plant 

 embryologists of the future will almost certainly be largely preoccupied 

 with cellular physiology and, in particular, with the intricate details of 

 the action of hormones and kindred substances. The hterature thus far 

 available (reviewed by Murneek (1937), Wittwer (1943) and Britten 

 (1950) ) indicates that the developing seed should be viewed as a dynamic 

 system, conspicuous features of which are the localisation and utilisation 

 of the products of assimilation by the embryo. That auxin and other 

 growth-regulating substances play an important part in this process is 

 borne out by an increasing body of experimental data, (see Murneek, 

 1937; Avery et al, 1942; Wittwer, 1943; Haagen-Smit et al, 1946; 

 Britten, 1947, 1950). 



STARCH ACCUMULATION AND UTILISATION IN THE OVULE 



The literature of plant embryology contains only scanty information 

 on the translocation, utilisation and accumulations of nutrients. The 

 relation of nutrition to embryonic development has been explored by 

 Buell (1952) for Dianthus, a genus in which the suspensor consists of 

 two large basal cells. At the spherical embryo stage, the prevascular 



