Grinnellia americana, Harv. 15 



formed in the plane of the frond, growth begins in the third 

 plane, producing a papilla-like thickening in these portions 

 (Fig- 13)- 



The procarp consists of three cells and arises as a lateral 

 branch from one of the large joint-cells in the plane of the 

 frond (Fig. 14). In the haematoxylin preparations of mature 

 procarpic cells it is found that each contains a well-defined 

 nucleus within the densely granular, protoplasmic contents, 

 and that these cells are connected by open pores which 

 perforate their delicate cell-walls. The granular material 

 passing through these pores gives a beaded, strand-like 

 appearance to the protoplasmic connexion between adjacent 

 procarpic cells. The basal procarpic cell is frequently the 

 smallest in the branch and is connected with the supporting 

 cell by a pore, and not by a pit as are the four contiguous 

 thallus-cells which, with the supporting cell, form a charac- 

 teristic group in the floor of the young cystocarp. 



It is possible that the early connexions between the cells of 

 the procarpic branch were pits which became open pores by 

 the absorption of the delicate cell-wall at the points of 

 communication. 



The uppermost cell of the procarpic chain becomes the 

 carpogonium from which the trichogyne develops (Fig. 14 tr). 

 The trichogyne is subject to considerable variation. In some 

 instances it is branched and much elongated (Fig. i"] b); in 

 others it is simple, twisted, and of moderate length (Fig. 15). 

 The granular protoplasmic contents of the trichogyne are in 

 marked contrast to the clear gelatinous sheath enveloping it. 

 Just above the carpogonium, a knee-shaped enlargement 

 frequently occurs (Figs. 14 and 17 k). At this point the 

 longitudinal axis of the trichogyne changes its direction and 

 makes an angle of 30° to 40° with its former axis. This 

 enlargement on one side of the basal region may be the 

 cause of the changed direction of growth in the trichogyne, or 

 may be an accompanying phenomenon due to the resistance 

 which the young trichogyne must overcome when pressing 

 between the cells of the rapidly-forming pericarp. 



