210 



MONOGRAPH OF THE LABOULBENIACEiE. 



single " antheridial cell," or a group of such cells, the latter of a single naked or thin- 

 walled cell. 



If we separate the genera of Laboulbeniacece, on the basis above outlined, into 

 forms with endogenous and those with exogenous antherozoids, it will be found that 

 it is only in two aquatic genera that the forms included in the first-mentioned cate- 

 gory occur : Zodiomyces and Ceratomyces being the only instances in which this type 

 has been definitely observed. In general the antheridial branches are not highly 

 differentiated even in the more typical instances; while were the demonstration of 

 the existence of male elements of this type dependent on the data afforded by the less 

 well-marked examples, one might be inclined to doubt the presence of any sexuality 

 in such cases, despite the presence of a well-developed trichogyne. In Zodiomyces, 

 however, the antherozoids are produced in the form of buds which arise from the tips 

 of short special branches (Plate XXIII, figs. 21-23) which assume a rod-like form and 

 eventually fall from their attachment. These bodies have a definite wall and seem to 

 be sought by the tip of the trichogyne in a fashion to which reference will be made 

 below. A second well-marked instance is found in Ceratomijces rostratus, from the an- 

 theridial branches of which are developed rods of definite form and size, which 

 become separated and adhere to the trichogyne. In this instance the rods are formed 

 successively from a definite point at the distal end of the fertile cells of the anthe- 

 ridial branch (Plate XXIV, figs. 23-24), each rod usually becoming detached from its 

 point of origin before its successor has begun to form. In other species of the genus, 

 however, these bodies are not so clearly differentiated, and seem to be replaced by 

 slender, often long, filaments which eventually break up into rods that are presum- 

 ably functional as antherozoids. The adherence of the antherozoids to the mother- 

 cell, or to one another, as in the last two instances mentioned, may be assumed to 

 render fertilization more certain ; since it is evident that were such bodies separated, 

 as soon as they were mature, from a plant growing, as in the present instance, on an 

 isolated and rapidly swimming host, the chances of their ever coming in contact with 

 and adhering to the trichogyne would be reduced to a minimum. In view of the fact 

 that this separation does not seem to take place at once, and that the long slender 

 trichog}me must, from its position, inevitably be continually brought into contact with 

 them while still in situ, through the motion of the plant which would necessarily 

 result from the activities of its host, it seems quite probable that such antherozoids, in 

 order to be functional, must become detached at the moment when they come in con- 

 tact with and adhere to the trichogyne. 



In all other genera of the family the antheridia are more complicated in 



