ioo Morphology BOOK i 



as it approached the embryo sac. Pringsheim and Stras- 

 burger compared it to the canal-cell in the archegonium 

 of the Cryptogams. Sachs held as they did, that the 

 two germinal vesicles corresponded to two archegonia, 

 the basal rounded part of each being the oosphere, and 

 the elongated apex the canal-cell, which became separated 

 from the other only after impregnation. 



The antipodal cells were recognized quite early, but no 

 account of the method of their formation was given for 

 some years. Pfeffer held them to be a rudiment of the 

 true prothallium. 



More exact knowledge of the true condition of things 

 came to light in the years 1877-81, when, through the 

 concurrent investigations of several workers, the progress 

 of the development of the sexual apparatus was ascertained. 

 Among the many writers who treated of the subject may 

 be mentioned Warming (1877), Vesque (1878-9), Strasburger 

 (1879), Fischer (1880), Marshall Ward (1880), Treub and 

 Mellink (1880), and Guignard (1881). Their accounts agreed 

 in all essentials, and were confirmed and extended by many 

 researches in more recent years. 



The homologies of the egg apparatus and the antipodal 

 cells in the light of the new discoveries were sought for 

 in two directions. Warming and Vesque considered that 

 the cell which develops into the embryo-sac is equivalent* 

 to one of the spore mother-cells in the sporangium of a 

 Pteridophyte, and without regarding the probability of a 

 prothallial development, held that the early accumulation 

 of four nuclei at each end indicated a tetrad of spores. 

 How fertilization of one of them was possible, if such was 

 their nature, remained unexplained. 



. Strasburger put forward the other hypothesis : he 

 considered the embryo-sac to be a spore mother-cell which 

 develops into a single megaspore, and the structures 

 arising later to be its prothallium. He held these to 



