EXPERIMENTAL EMBRYOLOGY 



383 



no known method of overcoming this trouble, it is not necessary to 

 discuss the point further. 



Embryo Culture. In the preceding section we have considered 

 the methods for overcoming some of the barriers to fertilization. 

 It has frequently been observed, however, that even after gametic 

 fusion has taken place something may arrest the growth of the 

 embryo so that the resulting seeds are nonviable (see Sachet, 1948). 

 Recent research has shown that in such cases it is frequently possible 

 to excise the young embryos from the ovules and grow them in 

 artificial media (Figs. 204-208) — a process not unlike the famous 



Fig. 205. Excised embryo being transferred to sterile culture bottle. 

 Randolph, 1945.) 



(After 



Caesarean section in which an immature animal embryo is removed 

 from the body of the mother and grown in an incubator. 



In tracing the development of this new technique of embryo 

 culture, we find that Hannig (1904) was the first to make a success- 

 ful attempt of this kind. Using certain crucifers (e.g., Raphanus 

 and Cochlearia) as the objects of his study, he tested a variety of 

 nutrient media containing sugars, mineral salts, plant decoctions, 

 certain amino acids, and gelatin. Mature plants were reared from 

 embryos that were only 1.2 mm. in length at the time of their 

 excision, but presumably the radicle, plumule, and cotyledons had 

 already been formed at this stage. Following Hannig, Stingl (1907) 

 grew embryos of several cereals, but instead of placing them in 

 culture media he transferred them to the endosperms of other genera 



