NEW MYXOPHYUEAE FROM PORTO RICO 



35 



ments; cells quadrate to one-half or one-third as long- as the 

 diameter in rapid division; cross walls very conspicuous, at 

 times as thick as the length oL' the adjacent cells; end cell 

 rounded, wall not thickened. 



Growing on nmd and floating among other algae in a pool 

 near Laguna Gruanica, no. 1822, type ; in a pool four kilometers 

 north of Mayagiiez, nos. 1312 a, 1327 h, and 1329 ; on damp rocks 

 about twelve kilometers north of Utuado, no. 1514 h. 



This species of Oscillatoria is well marked by the conspic- 

 uity of the cross cells. They are very white and relatively wide, 

 giving the trichomes the appearance of being jointed. It ap- 

 pears to be a relative of the tenuis group. 



Oscillatoria articitlata circinata var. nov. 

 Plate 7, figure 65 



Trichomes short and circinate, making several complete 

 turns, otherwise as the species. 



Growing about four kilometers north of Mayagiiez, no. 

 1329 u, type. Specimens of this form have been seen in collec- 

 tions under various numbers but the cause of the peculiar habit 

 of rolling up 1 am unable to explain. 



Comparable perhaps with Oscillatoria gloiopliila Grun. but 

 is smaller and lacks the granules at the cross walls reported in 

 that species. 



Oscillatoria tenuis levis var. nov. 



Plate 1, figure GG 



Plants not forming a definite stratum, but distributed among 

 other algae ; trichomes 6.8-7.8 n diam., not constricted, end walls 

 decidedly thickened; contents homogeneous or with a few scat- 

 tered tine granules in rapidly dividing cells. 



Floating among numerous other algae, both Chlorophyceae 

 and Mj^ophyceae, in the Turabo River near Caguas, no. 486 a, 

 type ; in a ditch along the way to the Playa, Fajardo, no. 696 h. 



Most of the plants referred to 0. tenuis Agardh do not have 

 the end walls thickened. Gomont does not figure them in his 

 monograph of the Oscillariees as having capitate or thickened 

 ends, although according to his description the end wall should 

 be slightly thickened. 



The plants described here vary from the species in having- 

 decidedly thickened end w^alls, in not being constricted at the 



