OP ARTS AND SCIENCES. 57 



to be flat or tabular, with often a very irregular outline. They may 

 then, in a geiil-ral way, be said to be of a lenticular shape, although 

 they do not often approach the circular in form. They always 

 lie with their flattened faces presented to the interior surface of 

 the cystocarp, and consequently a vertical section, if it be not tan- 

 gential, always exhibits the cells in their fusiform appearance. The 

 amount of gelatinous intercellular substance between these cells is 

 much smaller than is found elsewhere, except perhaps in the growing 

 terminal part of the frond. 



It is on cells very like the ones just described, {)erhaps somewhat 

 thicker in proportion to their other dimensions, that the carpospores 

 are borne. The cells from which the spores arise lie directly inside of 

 the conceptacular wall, and are, as has previously been said, closely in- 

 terwoven with it. They have no peculiarities in shape or structure 

 which distinguish them from the sterile cells forming the wall. 

 They do not, however, like the latler, always present their flat 

 faces inwards, but are more irregularly arranged. The spores are 

 borne from the ends or angles of the cells, or from protuberances 

 arising from their flat surface (Figs. 15, 16). The entire surface of 

 the cavity is lined with the spores, except in the immediate neigh- 

 borhood of the carpostome (Fig. 14). They are not arranged in chains, 

 but are borne singly. In shape they are irregularly ovoid or pyri- 

 form, with tap»ring and sometimes acute apices. A small basal cell 

 is always found between the spores and the spore-bearing cells proper. 

 From the basal cell there arises a sterile filament that always appears 

 to be present (Figs. 15, 16). This paraphysis is usually somewhat 

 longer than the spore, but as it arises from the side, and not the top, of 

 the basal cell, it extends out no farther. Its contents are almost hya- 

 line, in contrast with those of the spore. In the mature cystocarp the 

 spores are directed inwards, and somewhat upwards, towards the carpo- 

 stome, almost completely filling the cavity. The ripe spores are highly 

 granular, somewhat darker in color than the other tissues of the plant, 

 and have distinct nuclei. That the cystocarps examined were ripe, 

 there can be no doubt. Some specimens collected on December 23d 

 were placed uninjured in sea-water on a slide ; when they were exam- 

 ined, some fifteen hours afterwards, many spores were found to have 

 made their way out of the cystocarp, and to be lying loose in the sur- 

 rounding water. Attempts were made to germinate the carpospores 

 as well as the tetraspores, all of which failed, owing, no doubt, to the 

 same causes suggested in the case of the tetraspores. 



Before leaving the subject of the cystocarps, it is necessary to de- 



