NEW MYXOPHYCEAE FROM PORTO RICO 



71 



MiCROCHAETE TENERA tcnuior var. nov. 



Filaments scattored among- other algae, 4.8-6..") [^ diam., larg- 

 est at the apices ; trichomes 3.5-4.5 m diam. ; cells densely and 

 coarsely granular; resting spores 5-6 n diam., 7-11 n long, in the 

 central and upper parts of tlie tricliome in broken series of 2 to 

 16; spore wall smooth, brown. 



Growing among Hepaticae in company with other algae by 

 the road near Adjiintas, no. 1571, type. Collected by Elizabeth 

 G. Britton. 



The variety tenuior differs from the species in being smaller 

 in all of its measurements and in having the resting spores oc- 

 curring either singly or in broken series, variable in number, 

 and in size. Very little has been said of the spores in M. teuera. 

 Forti (in De Toni, Syll. Alg. 5; 483) says they are cylindrical 

 and seriate. 



Rivularia (Gloeotriciiia) flagelliformis sp. nov. 



Plate 14, figure 25 



Thallus globose to irregular, very soft and gelatinous or mu- 

 cilaginous in consistency, about 1 cm. diam.; trichomes a con- 

 siderable distance, from each other, constricted at the dissepi- 

 ments throughout except the terminal hair in the juvenile stage, 

 but on nearing maturity the condition disappearing except with 

 a few cells at the base, up to 1 mm. long, 5.5-6.8 p diam. at the 

 base before spore formation begins, tapering gradually from the 

 base to the apex, terminating in a long hair 1-1.8 \i diam. ; cells 

 granular, aeruginous, mostly quadrate, hair cells 4—6 times as 

 long as broad ; heterocysts hyaline, mostly spherical, 11-14 m 

 diam., others vary from ellipsoidal to conical; sheath undulate, 

 hyaline, visible for about 80 m, then vanishing into the common 

 transparent gelatinous tegument ; spores densely congested with 

 very fine granules, 11-14 m diam., up to 80 n long. 



Growing in a Avater reservoir near Eio Piedras, no. 126, type. 



Scytonema evanescens sp. nov. 



Plate 15, figure 26 



Filaments 450-650 p long, adhering by their gelatinous 

 sheaths into a dense stratum, mostly erect, considerably con- 

 torted and more or less parallel, 25-32 \\ (up to 40 m in the apical 

 region) diam.; trichomes clavate, the widest part at the apex of 



