﻿324 BOTANICAL GAZETTE [may 



Golenkln's (1899) studies of Sphaeroplea are incomplete in cer- 

 tain cytological details of oogenesis, and the fact that the eggs 

 of some forms are uninucleate suggests caution before laying 

 emphasis on the multinucleate condition. It is possible that 



further study will relate the multinucleate eggs to the uninucle- 

 ate, as in Saprolegnia. 



What evidence have we of the second possibility, /. ^., the 

 origin of the coenogamete from a multinucleate gametangium 

 which, ceasing to form uninucleate sexual cells becomes itself a 

 coenocytic gamete ? Most important is the exceedingly interest- 

 ing series of four species of Albugo described with so much 

 detail by Stevens (1901). We cannot take up this investigation 

 except to notice that the four species form a well-graded series 

 in which the evolutionary direction is clear and very important 

 for the conclusions that we are striving to establish. The 

 oospheres of Albugo Bliti and A, Portidacae contain many func- 

 tional gamete nuclei, that of A. Tragopogonis several potential and 

 several functional, and that of A, Candida several potential and 

 one functional. In this series the coenocentrum Is very small in 

 A, B/itt 3.nd A, Portidacae, larger in A. Tragopogonis, and very large 

 and strongly chemotactic in A, Candida. A fifth form has been 

 added to this series by Ruhland (1902), who finds that Albugo 

 Lepigoid is even more highly specialized than Albugo Candida, 

 since it contains an extraordinarily large coenocentrum. The 

 evolution in complexity is plainly from A, Bliti to A, ca?idida 



'pigofii 



the uni- 



» 



although it sacrifices a large number of nuclei in the conjugating 

 tube (trichogyne), and by this specialization presents conditions 

 more complex than the molds. 



nucleate. And this series offers the most striking evidence 

 against the evolutionary possibility considered in the previous 

 paragraph. 



Now, the multinucleate eggs of Albugo are not the most 

 primitive types of coenogametes, because they contain only a 

 portion of the total number of the nuclei in the gametangium, 

 many of the sister nuclei passing into the periplasm. They are 

 not as simple as the coenogametes of the Mucorales, nor yet as \ 



primitive as the oogonium of Pyronema, which has no periplasm 



f 



