18 MINNESOTA BOTANICAL STUDIES. 



The procarp and cystocarp. Procarps are borne terminally 

 on cortical filaments having the aspect of the ordinary immature 

 filaments of that area. They were never found produced by 

 the primary cortical filaments of the growing point, but they are 

 often borne on some of the earlier formed secondary filaments 

 and are often abundant a very short distance behind the grow- 

 ing tip of a branch. They are also often produced on the 

 younger filaments of much older cortical branch systems, and 

 it is not uncommon to find procarps and mature cystocarps close 

 together in the same branch system of cortical filaments. In 

 the development of the procarp the wall of the terminal cell of 

 a young cortical filament becomes thickened, particularly about 

 the distal parts of the cell, and a terminal cylindrical outgrowth 

 appears {Figs, p, 10). This outgrowth, the trichogyne, increases 

 in length until, in the mature procarp, it may reach 150 mic. in 

 length, projecting beyond the gelatinous matrix of the frond. 

 In all immature procarps the protoplasm of the trichogyne 

 was continuous with that of the carpogonial cell. No entirely 

 mature and unfecundated procarps were seen. Many mature 

 procarps with attached sperms were found, and in these the 

 protoplasmic contents of the trichogyne were always much con- 

 stricted and often broken at intervals and separated from the 

 contents of the carpogonial cell. 



The carpogonial cell and the trichogyne are from the first 

 devoid of floridean starch. 



The cell immediately proximal to the carpogonial cell is 

 specialized as an auxiliary stalk cell (Figs. 10-16, a). During 

 the earlier stages of the development of the trichogyne, the cell 

 is scarcely to be distinguished from the sterile cells of the fila- 

 ment. As the trichogyne approaches maturity the auxiliary 

 stalk cell rounds up, becoming wider than the adjacent cells, 

 and it may be further distinguished from the proximal cells of 

 the filament by its dense cytoplasm, and by containing very 

 little floridean starch. It undergoes little further change during 

 the development of the cystocarp. 



After fecundation the trichogyne soon withers, but the basal 

 portion may persist for a considerable time (Fig. 14). Its 

 remains may occasionally be seen in the half developed cysto- 

 carp, but never when the cystocarp is mature. 



The fecundated carpogonial cell soon divides transversely 

 into two unlike cells. The proximal cell thus formed is almost 



