Evans: Air chambers of Grimaldia fragrans 241 



are shown, but the cells enclosed present a very different appearance. 

 They are not only much more numerous but are, with a few excep- 

 tions, more or less firmly united, and the entire chamber is thus 

 divided up into smaller chambers, some of which seem entirely 

 cut off while others show their connections with other chambers. 

 The seven cells shown on the right of the left-hand partition in 

 Fig. 3 are represented in FiG. 4 by seven united cells, showing at 

 once that these seven cells are not the cross sections of filaments 

 but simply the cross sections of teeth, like those shown in Fig. 2. 

 Similar conclusions would be created by comparing other apparently 

 free cells in Fig. 3 with their representatives in FiG. 4. It thus 

 becomes established that there are no free filaments in the cham- 

 bers. It will be noted further that FiG. 4 presents a much more 

 complicated condition than Fig. 3 and that the boundaries of the 

 air chamber would be hardly 

 distinguishable except through 

 comparison with the simpler fig- 

 ure. It is probable that a sec- 

 tion like the one shown in Fig. 4 

 was responsible for Schiffner's 

 statements, which it certainly 

 strongly supports. 



In Fig. 5 a section from 

 another thallus is shown, cut at 

 a still lower level. This section 

 shows a loose spongy tissue, two 

 of the chambers being connected 

 by a passageway. Cellular out- 

 growths are very infrequent, but 

 a single cell, apparently free, is 

 shown in one of the chambers, 

 and a single short outgrowth in 

 another. When compared with 



Fig. 4 the spaces are relatively larger and fewer and the tissue in 

 consequence much less compact. Sections cut farther down show 

 elongated spaces, similar to those represented in Fig. 2, while 

 sections beneath these show the ventral parenchymatous tissue 

 without spaces of any sort. 



Fig. 5. Section parallel with the 

 surface below the dorsal layer of cham- 

 bers, X 270. 



