272 ME. W. WEST ON SOME FEESHWATEE 



The nearest species to this hitherto described is H. laminosiis, 

 Hansg. [" Ueber den Polymorph, der Alg.," Botan. Centralb. 

 1885, p. 48 {cfr. Boriiet et Flah. Eevis. des Nostoc. Hetero- 

 cjst. p. 55)], from which it differs, however, in not being 

 calcified in any way, in being a little larger, in having its single 

 and. unfrequent branches of a similar thickness to the primary 

 filaments without any attenuation, and. in its peculiar habitat. 

 The heterocysts are of the same breadth as that of the cells (or 

 narrower), whilst those of H. laminosus are often broader. 

 Like the latter, the threads are very variable, being sometimes 

 similar to an Anabcena, sometimes like a Lynghya^ while at other 

 times the cells are quite irregular and somewhat inflated. Some 

 examples showed the rounded granulose bodies noted by Hansgirg 

 in H. laminosus (Bemerkungen zur Systematik einiger Siiss- 

 wasseralgen, p. 18). These bodies when fully formed appear 

 to be thick-walled (figs. 23-28) and have a diameter of 6-13 /u. 



The cell of the primary filament immediately under a branch 

 always projects more or less into the sheath of the branch. 



25. Hapalostphon FLExrosus, Borzi. {Alghe d'acq. dole. d. 

 Bapua^ in Nuovo Notarisia, Apr. 1892, p. 43.) 



Crass, fil. 7'5-8*5^ ; crass, cell. 5-5-6 ;u; long. cell. 4-4'5 /i. 

 Hah. In stream, Grande Soufriere, Dominica. No. 884. 



26. H. AEBOEEUs, nov. sp. (PI. Xy. figs. 1-3.) 



H. inter alias algas repertus ; filis primariis flexuosis, passim 

 ramosis uno latere e cellulis singulis ibrmatis, eellulis diametro 

 1-1 ^plo (rarius 2plo) longioribus, vagina arcta, tcnui, et achroa ; 

 filis secundariis brevibus, crassitudine filis primariis similibus sed 

 subtenuioribus, cellulis diametro subicqualibus ; heterocystis 

 quadrato-oblongis, intercalaribus. 



Crass, fil. 7-10^; crass, cell. 7-9"5 /ii ; heterocyst. 6-9 /x 

 x9-ll^. 



Hah. On trees, summit of Trois Pitons (4500 ft.), Dominica. 

 No. 903. 



The nearest species to this is H.Jlexuosus, Borzi (/. c), from 

 which it differs in not possessing flexuose intricate branches on 

 every side ; it is also a rather larger species, with cells often a 

 little longer than broad and never depressed. 



27. Stigonema noEMOiDES, Bornet et Flah. {Bcvis. des Nosfoc. 

 Heteroci/sf. p. (ID.) [Scytonema hormoides, Kurtz. Sirosiphon 

 brevis, Kuetz. Botan, Zeit. 1847, p. I'JG ; Tahulce phycolog. ii. 



