40 



Fig. 36. Acrochsetium opetigenum nov. spec. 



a, Transverse section of Dasya elegans with basal 

 parts of three plants two of which fixed to the base 

 of a pinnule and showing the cuneate endophytic 

 process penetrating into the tissue of the host and 

 one fixed to the pinnule itself, b, basal part of an 

 older vigorous plant showing the endophytic cuneate 

 process and further two short epiphytic branchlets ; 

 from that to the left an erect filament is issued. 

 (About 200: 1). 



pedicellate examples 

 also occur. The spor- 

 angia are placed 

 upon the lowermost 

 cells of the branches 

 mostly only two or 

 three upon each fila- 

 ment ; but they also 

 occur upon the main 

 filaments. 



COLLINS has de- 

 scribed an Acrochse- 

 tium (A. Dasyae) also 

 found upon Dasya 

 elegans which seems 

 closely related to the 

 present species. It 



has for instance the same globular persistent basal spore but this 



emits, as described by COLLINS, "a short, descending process, some- 

 times branched, of a few small rounded cells, 



attached to the host". I have examined the 



specimens, distributed in Phycotheca Bor.-Am., 



No. 1342 and have seen these short, 2 3 celled 



branches. As far as I can observe these branches 



are not endophytic and they are upon the whole 



quite different to the descending process found 



in my plant. Besides this difference my species 



has a very different appearance, is much larger 



in all parts of the thallus, much more branched 



and the ramification is not secund. 



Found upon Dasya elegans in a depth of 



about 20 meters. 



St. Jan: Off Cruz Bay. 



12. Acrochsetium robusttiin nov. spec. 



Thallus ceespitosus, usque ad 1 mm longus, 

 e filis erectis et filis horizontalibus epiphyticis 

 compositus. 



Spora germinans in texturam hospitis pau- 

 lum penetrans ; a superiori parte, non immersa, 

 fila brevia repentia, plus minus lateraliter con- 



Fig. 37. Acrochse- 



tium opetigenum 

 nov. spec. Sporan- 

 gia-bearing filaments 



with chromato- 

 phores and pyreno- 

 ids. (About 400:1). 



