MONOGRAPH OF THE LABOULBENJ ACEM. 



211 



structure, consisting of highly specialized cells, or groups of cells, within which the 

 antherozoids are formed endogenously and from which they are discharged through a 

 special orifice in the form of free, naked, or nearly naked protoplasmic masses. 

 Among such antheridia two distinct classes may he clearly distinguished, which 1 have 

 (culled simpk&nd compound, respectively: although instances occur in which antheridia 

 of the " simple " type are so closely associated that they may he regarded as tran- 

 sitional forms between the two types. In the first class, the simple form is character- 

 ized by the fact that the antheridial cell is quite independent of any similar cells, 

 however closely they may be united to it, and discharges its antherozoids into the 

 surrounding medium through its proper mouth. In the second instance, on the other 

 hand, several such cells, closely associated to form a specialized organ, discharge their 

 antherozoids into a common cavity from which the latter make their escape into the 

 surrounding medium through a single aperture. 



The simple antheridium (Plate II, fig. 15) is usually a more or less flask-shaped cell, 

 which may be solitary or associated with similar cells grouped together with or with- 

 out regularity. Although in Amorphomyces, a genus wholly destitute of appendages, 

 it results from the direct modification of the terminal portion of the germinating 

 spore (Plate V, figs. 20 and 23), it originates in other genera as a terminal or lateral 

 outgrowth from the appendage or its branches. In a majority of genera, if it does 

 not terminate the appendage or one of its branches or branchlets, the antheridium is 

 itself a branchlet, as, for example, when it is sessile ; but in a few instances this termi- 

 nal character is lost and the organ is formed as a definitely intercalary cell, as in 

 Rhadinomyces. In the compound type, these cells seem always to be intercalary 

 in origin, although material has not been available for the study of their development. 



The form of the simple antheridium is remarkably constant, the single cell of which 

 it is composed being distinguished, more or less abruptly, into a basal, somewhat in- 

 flated portion or venter ; and a terminal, more slender, usually sub-cylindrical portion, 

 the neck, originally developed as a terminal outgrowth, which, at maturity, becomes 

 perforate at its apex for the discharge of the male elements. The cavity of the ven- 

 ter is separated from that of the neck by a kind of diaphragm, abruptly distinguished 

 on the venter side, and much less so on the neck side. This diaphragm, which seems 

 to be formed by the deposition of a ring of cellulose in the position indicated, is per- 

 forate in the middle so as to allow the contents of the venter to pass out into the neck 

 through an opening which is much smaller than the diameter of the cavity of the 

 neck itself (Plate I, fig. 26). The cavity of the neck therefore, which may be 

 conveniently called the canal, though of about the same diameter throughout the 



