136 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. lv. 



Criticism of the Views with regard to the Embryo-sac of 

 Angiosperms. By Gustav Mann, 



The author presented in the first instance a historical 

 sketch of the literature dealing with the structure and the 

 development of the emljryo-sac, from Malpighi's description 

 of the ovary of Amygdulis up to Westermeyer's paper on 

 the antipodal cells, showing how gradually our knowledge 

 has been a(jquired. "He then opposed the view that the 

 embryo-sac of Angiosperms is a raacrospore, and finally 

 called specially the attention of the Society to the fact that 

 in the formation of the secondary or definitive nucleus, the 

 fusion of the two nucleoli is the essential and final step in 

 the act of conjugation of two sexual cells. He said : — 



All leading botanists interpret the embryo-sac of Angio- 

 sperms as a macrospore, which by germination gives rise to 

 an eight-celled prothallus, in opposition to Warming and 

 Vesque, who regard tlie same as the equivalent of a special- 

 spore-mother-cell, and the eight nuclei within the embryo- 

 sac as two sets of four macrospores derived from two 

 sporocytes. As these opposing views are fully discussed 

 by Marshall AVard in two very able papers,"^ and as their 

 author has brought forward a new suggestion, namely, that 

 the eight nuclei correspond to two four-celled prothalli, 1 have 

 criticised the pro's and contra's given in the quoted papers 

 in the light of new facts discovered in my study of the 

 develoi)nient of the ovule of Myosurus minirmis. 



Warming, Strassburger and Ward state that only the 

 periclinal walls formed by the division of the embryo-sac- 

 mother-cell show a gelatinous degeneration ; but this is 

 decidedly not the case in Myomrus, a type wliich has also 

 been studied by these three authorities, since all the walls of 

 tiie embryo-sac-mother-cell, after its division into a row of 

 cells, undergo this peculiar change, the only sides excepted 

 being those abutting on the dermatogen and the plerome- 

 eleraents ; the reason of the latter side not undergoing the 



* Ward, ill Linn. Soc. .lourii. iiot., vol. xvii., and in Quart. Journ. 

 Microscop. Sc, .Januaiy 1880. 



