102 Morphology BOOK i 



Various curious appearances of the development of 

 different parts of the embryo-sac, and particularly of its 

 antipodal contents, suggested that haustoria are often 

 developed, generally after fertilization. Cases were observed 

 by Guignard in 1885, and by Johnson in 1889. Other 

 instances have been noted since the close of the century. 



The prothallus of the Gymnosperms and its homology 

 with the endosperm of Selaginella and Isoetes were known 

 to Hofmeister. It is interesting, in the light of the possible 

 sexuality of the synergidae, to find that in 1898 V. H. Black- 

 man determined the ventral canal cell of Pinus sylvestris to 

 be an arrested gamete. Chamberlain came to the same 

 conclusion in 1899, as the result of a study of Pinus 

 Laricio. The details of the development of the archegonia 

 and the separation of the ventral canal cell from the 

 oosphere were studied in 1879 by Strasburger. 



The details of the process of fertilization were not known 

 with any accuracy in 1860. The fusion of the cells had 

 been observed, but there was no clear idea of what the 

 fertilizing substance consisted. Sachs said in the Lehr- 

 buch as late as 1874, that fertilization consists of a union 

 of the fertilizing substance of the male cell with the proto- 

 plasm of the female. The entrance of the antherozoids of 

 the Cryptogams into the archegonium was observed by 

 Hofmeister, but their penetration as far as the oosphere 

 was first observed by Strasburger. The penetration of 

 the embryo-sac by the pollen tube not having been seen, 

 except in the solitary instance of Canna, Sachs suggested 

 that in Phanerogams a union by diffusion takes place of 

 some substance contained in the pollen tube with the 

 germ cell, and that the contact of the tube with the apex 

 of the embryo-sac is sufficient for its transmission. 



The part played by the nuclei was first observed by 

 Schmitz in studying the conjugating cells of Spirogyra in 

 1879, and their fusion in Angiosperms was discovered by 



