56 PROCEEDINGS OP THE AMERICAN ACADEMY 



The ripe cystocarpic fronds can usually be distinguished from the 

 others by the fact that they are more or less lobed, each lobe con- 

 taining a single cystocarp (Fig. 2). This is not a very reliable dis- 

 tinction, however, for when a frond contains only one cystocarp, 

 which not infrequently happens, its shape closely resembles that oF a 

 tetrasporic or sterile frond. On the other hand, the other fronds are 

 sometimes lobed, from abnormal conditions of growth, in manner not 

 unlike the cystocarpic specimens. Thus it will be seen that it is im- 

 possible to tell certainly, without microscopic examination, in what 

 state any particular frond may be. In the majority of the cysto- 

 carpic fronds there are several — from two to five — cystocarps pres- 

 ent, though a considerably larger one is, as has already been said, 

 often found in place of many. 



Although it might seem to indicate, from the division of the frond 

 into lobes, that the cystocarps are in this instance external, closer 

 search shows that this cannot be considered to be the fact ; the growth 

 of so large a body as the cystocarp in so small a frond naturally neces- 

 sitates the condition found, and even as it is the lobes represent more 

 than merely the couceptacles themselves, for the ordinary tissues of 

 the frond go in part to make them up (Fig. 14). The cystocarps are 

 ovoid to almost spherical in shape, with the smaller end external. 

 They may be readily separated from the surrounding cells by a little 

 careful dissection, when they appear as small white dots, scarcely 

 visible to the naked ey%. From a vertical section of a cystocarp a 

 very good idea of its structure may be obtained (Fig. 14). The cells 

 surrounding the cavity in which the spores are borne are seen to be 

 more closely compacted than those of the rest of the frond, and of 

 a different shape. This closely compacted wall consists chiefly of 

 st'erile cells, with which on the inner surface the spore-bearing cells 

 are intricately associated. The conceptacular wall is always thickest 

 at the inner end of the cystocarp, gradually becoming thinner as it 

 approaches the outside, being represented in the region of the carpo- 

 stome by a single layer of cells. The carpostoine, which has always 

 been seen in these cystocarps, consists of a small circular opening 

 throush the cellulose covering of the frond. It is situated at the 

 small end of the cystocarp, where it approaches nearest the exterior 

 of the frond. The cells which compose the wall of the cystocarp, 

 when viewed in vertical section, are seen to be either spindle-shaped 

 or very thin and almost fiiliform (Fig. 14). This is due to the 

 collection of the protoplasm of the cell at the centre, leaving but 

 a small amount at the extremities. Other aspects show the cells 



