No. 454-] STUDIES ON THE PLANT CELL. 



751 



coenogametes is less perfectly uniderstood. The multinucleate 

 character of the fusing gametes is well known, but the later dis- 

 tribution and fate of the sexual nuclei has not been followed, and 

 it is by inference that we believe these coenogametes to behave 

 in essentially the same manner as those of Albugo and Pyronema. 



Coenogametes fall into two classes according as they involve 

 all of the protoplasm contained within the mother-cell or only a 

 portion of such protoplasm. The first group probably represents 

 the simplest and most primitive conditions. 



Coenogametes of the first class are found in the Mucorales 

 (Gruber :oi) and in the Gymnoasceae (Dale, :03). In these 

 types the entire contents of the terminally formed sexual cells 

 unite to produce the zygospore in the former group and the 

 fertilized ascogonium in the latter, from which arises the system 

 of ascogenous hyphse. 



Coenogametes of the second class contain only a portion of 

 the protoplasm in the mother-cell which is usually a terminal 

 structure. The protoplasm that is not involved in the coeno- 

 gamete proper generally bears some important relation to the 

 sexual element. Thus the periplasm of the Peronosporales 

 assists in the formation of the wall of the oospore and the con- 

 jugation tube of Pyronema becomes the path through which the 

 contents of the antheridium enters the ascogonium. But in 

 some forms the superfluous protoplasm is merely cut off from 

 the coenogamete as a sterile cell (Monascus). In Albugo and 

 Pyronema the sterile and fertile portions of the protoplasm are 

 so closely associated that the mother-cell really acts as a whole, 

 very much as the simplest types of coenogametes which shows 

 the close relationships between the two. Moreover the anthe- 

 ridia of these forms are types of coenogametes almost as simple 

 as those of the molds or the Gymnoasceae. 



The coenogamete is a type of sexual cell unknown in the 

 animal kingdom and among plants is probably restricted to the 

 Phycomycetes and Ascomycetes. The problems of its homol- 

 ogies and origin are very interesting. 



The simplest types of coenogametes (Mucorales and Gymno- 

 asceae) are cells situated at the ends of filaments in the same 

 position as the sexual organs of the Siphonales. The mother- 



