25 



Fila erecta parce ramosa, 5 6^ lata, 

 cellulis diametro triplo vel 4 plo longioribus, 

 cylindricis, in parte superiori filorum cellulis 

 tenuioribus, 3 4// latis, chromatophorum, 

 ut videtur, parietale pyrenoide laterali 

 munitum continentibus. 



Sporangia monospora, fusiformia apice 

 truncate, sessilia aut pedicellata, sparsa 

 aut unilateraliter seriata, 4 5/* lata, 10 

 11^ longa. 



This small species was found upon 

 old leaves of C aider pa taxifolia. Only a 

 single tuft was met with growing in com- 

 pany with Acrochsetium seriatum and other 

 small epiphytes. 



It forms a dense low tuft up to about 

 400 it high. 



The basal part consists of creeping 

 filaments (Fig. 17 d) fusing more or less 

 together but, it would seem, easily separ- 

 able. The cells in these filaments are Fig.17. Acrocheetium netro- 



rather short, often nearly isodiametric but ca> 'P um nov. spec, a, b, c, 



J parts of filaments with 



much irregular in shape. From nearly all sporangia, d, base of the 



of these cells with the exception of those P^ 11 ,*;^ l a ' 3 nXX 1 '-,^*' c> 



4-r\() * J " ft |il )l | " | 



near the margin erect filaments arise. 



These (Fig. 17 a) are multilaterally ramified but not much so, 

 and taper somewhat towards the upper end (Fig. 17 c). They 

 consist of cylindric cells about 18 20// long; in the basal part 

 these cells are about 5 6 p broad while those at 

 the summit are only 3 4//. 



The shape of the chromatophore was not clearly 

 visible, so far as I have been able to see it was 

 parietal with a lateral pyrenoid ; the last mentioned 

 was more visible in the sporangia (Fig. 18). 



The latter have a very characteristic shape 

 (Figs. 176, 18) ; they are fusiform with a truncate 

 lg summit, about 4 5 p broad and 10 11 fj. long. 

 Acrochsetium They are mostly sessile but often also pedicellate. 



netrocarpum They occur more or less in a series or may be more 

 nov. spec. J 



Filament with scattered. 



sporangia. 

 (About 

 800 : 1). 



This species has only been found once namely at Chri- 

 stianssted, St. Croix. 



