Clathroptychium. 51 



very rudimentary, but in C. Berkeleyi are often broader than 

 the triangular portion, and recalling to mind the similar struc- 

 ture in Enteridium olivaceum. The triangular upright threads 

 almost invariably show traces of a central cavity, which cor- 

 responds to the intercellular space between the originally 

 cylindrical sporangia. The persistent apices of the sporangia, 

 when viewed from above under a low power, are seen to consist 

 of very slightly convex hexagons, rarely pentagons, so firmly 

 agglutinated together that the whole can be removed as a 

 continuous membrane ; if this is done, and the membrane then 

 viewed from the under side, after the spores have been cleared 

 away, the stumps of the triangular threads will be seen to 

 originate from the angles where the permanent apices of three 

 sporangia meet ; if this membrane is treated with potassie 

 hydrate, the apices separate from each other as do also the 

 triangular threads; this separation sometimes takes place in 

 water alone, when the apices with their threads appear as 

 represented in Rostafinski's figures 28 and 29. 



The above account applies to the typical structure, but both 

 species appear to be very variable. Zopf has figured an aberrent 

 form of C. rugulosum, having the threads supporting the apical 

 persistent portion of the sporangium varying in number, irregu- 

 larly branched and anastomosing. I have met with a similar 

 form, also another variety where the threads are branched and 

 anastomosing and not confined to the margin of the apical 

 portion, but originating from any portion of its under surface, 

 and approximating so closely in structure to certain forms of 

 the genus Perichaena as to be almost indistinguishable. 



Distrib. Europe; Africa; India; Ceylon; Australia; United 

 States : species 3. 



Clathroptychium rugulosum, Host. (f. 25 28). 



Hypothallus well developed, often extending as a whitish 

 membrane for some distance ; sporangia prismatic, apex slightly 

 rounded, and supported by five or six slender triangular per- 

 sistent threads, the fiat face pointing to the interior of the sporan- 

 gium rugulose ; colour of mass of sporangia reddish, bright 



