300 EMBRYOGENESIS IN PLANTS 



adventive embryos; no endosperm was formed, however, and there 

 was no further embryonic development. From these experiments it 

 could be concluded that growth-regulating substances have some part 

 in the induction of adventive embryos, but that, in the absence of 

 endosperm, the general or special nutrients required for the further 

 embryonic development are not available. 



EMBRYO CULTURE 



In growth and other studies of embryos, it is desirable, if not 

 essential, to be able to induce ovum development and to culture embryos 

 of all ages in media of known composition. Maheshwari (1950, 1951) 

 has summarised the literature on embryo culture from its inception at 

 the hands of Hannig (1904) to the present day. Hannig showed that 

 crucifer embryos, about 1-2 mm. long and therefore fairly well 

 developed, could be grown to adult plants in nutrient media containing 

 sugars, mineral salts, amino-acids, plant extracts and gelatin. Stingl 

 (1907) found that the embryos of various species of Gramineae could 

 be excised and successfully implanted in the endosperm of other genera. 

 Camara (1943) has recently confirmed these observations: indeed, he 

 observed that embryos of Triticum vulgare grew better when implanted 

 in the endosperm of Secale than in that of T. durum or T. turgidum. 

 Dietrich (1924) has recorded the successful culture of immature embryos 

 of a number of species in Knop's solution enriched with 2- 5-5-0 per 

 cent cane sugar and 1-5 per cent agar. Growth in such media had the 

 effect of eliminating some of the 'normal stages' of development, the 

 excised embryos growing directly into seedlings. It thus appears that 

 the normal morphological development of an embryo is largely deter- 

 mined by the nutritional status of its environment. Laibach (1925, 

 1929), while making some interspecific crosses in the genus Limim, 

 found that the cross L. perenne x L. austriacum yielded fruits of 

 approximately normal size; but the seeds were greatly shrunken and 

 only about half as heavy as the normal seeds. By dissecting out the 

 embryos and placing them upon damp blotting paper he was able to 

 induce their germination and the resulting plants flowered and fruited. 

 The reciprocal cross L. austriacum x L. perenne was more difficult, for 

 here the fruits were shed prematurely, the seeds being then only one- 

 thirteenth of the weight of normal seeds and incapable of germination. 

 However, embryos from this cross, if excised when about a fortnight 

 old and placed on cotton wadding containing 10-1 5 per cent cane sugar, 

 continued to grow. A couple of weeks later, when the embryos were 

 removed from the sugar solution and placed on moist blotting paper 

 they germinated within a few days and eventually yielded normal 

 vigorous plants. These observations have important implications, 



