NEW MYXOPHYCEAE FROM PORTO RICO 



59 



definite outline. The triehomes are relatively straight and short, 

 and the gelatinous matrix is not very firm, conditions commonly 

 met with in Anahaena. Knowledge of the developmental stages 

 may shed light upon the subject of its generic position. It be- 

 longs to the Dolichospernium section of the genus, having affini- 

 ties with A. inaequalis (Kuetz.) Born. & Flah. It differs from 

 that species in being smaller in all of its measurements. 



Anabaena unispora sp. nov. 



Plate 12, figure 8 



Stratum thin, slightly mucous, or triehomes intermixed with 

 other algae ; triehomes short, for the most part straight, slightly 

 attenuated for several cells ; cells cylindrical, slightly constricted 

 at the dissepiments, 4r4.5 m diam., 1.5-2 times as long as the 

 diameter, containing few to many small granules; terminal cells 

 blunt, heterocysts slightly larger in both dimensions than the 

 cells, one, or rarely two, in a trichome ; spores single, developing 

 at one side of the heterocyst, narroAvly to broadly ellipsoidal, 

 variable in size, 20-34 p long, 13-20 \\ broad, with a smooth thin 

 hyaline membrane, or at times the inner layer slighth' brownish 

 in color. 



Growing in a pool among other algae and debris near the 

 Park, Santurce, no. 49 a, type, no. 44 c, and no. 51 d. 



The very conspicuous character of this species of Anahaena 

 is the production of a single resting spore by each plant. The 

 large majority of plants produce but a single heterocyst, al- 

 though there are occasionally two in a plant. In case there are 

 two usually one is located near the end of the trichome and the 

 other near the center in its characteristic position. However, 

 no plants were seen with more than one spore. In number 47 c 

 of the collection, and in scattered filaments in several other col- 

 lections, the plants are young and the spores are sparse, but in 

 number 51 d the material is thoroughly mature and the spores 

 are numerous. It is difficult to ascertain its nearest relatives. 



Anabaena subtropica sp. nov. 



Plate 12, figlt.e 9 



Triehomes relatively straight and short, deeply constricted 

 at the dissepiments, 3.5-4.5 n diam. ; cells subcylindrical, approxi- 



