272 MR. W. WEST ON SOME FRESHWATER 
The nearest species to this hitherto described is H. laminosus, 
Hansg. [‘ Ueber den Polymorph. der Alg.,” Botan. Centralb. 
1885, p. 48 (cfr. Bornet et Flah. Révis. des Nostoe. Heétéro- 
cyst. 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. lJaminosus are often broader. 
Like the latter, the threads are very variable, being sometimes 
similar to an Anabena, sometimes like a Lyngbya, 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 Svstematik einiger Stss- 
wasseralgen, p. 18). These bodies when fully formed appear 
to be thick-walled (figs. 23-28) and have a diameter of 6-13 p. 
The cell of the primary filament immediately under a branch 
always projects more or less into the sheath of the branch. 
25. HaPaLostPHON FLEXUOsUS, Borzi. (Alghe d’acq. dole. d. 
Papua, in Nuovo Notarisia, Apr. 1892, p. 43.) 
Crass. fil. 7°5-8°5 w; crass. cell. 5-5-6 u; long. cell. 4-4°5 p. 
Hab. In stream, Grande Soufriére, Dominica. No. 884. 
26. H. arporetvs, nov. sp. (Pl. XV. figs. 1-3.) 
H. inter alias algas repertus ; filis primariis flexuosis, passim 
ramosis uno latere e cellulis singulis formatis, vellulis diametro 
1-}3plo (rarius 2plo) longioribus, vagina arcta, tenui, et acvhroa ; 
filis secundariis brevibus, crassitudine filis primariis similibus sed 
subtenuioribus, cellulis diametro subequalibus ; heterocystis 
quadrato-oblongis, intercalaribus. 
Crass. fil. 7-103 crass. cell. 7-9°5 pe; heterocyst. 6-9 p 
x 9-11 p. 
Hab. On trees, summit of Trois Pitons (4500 ft.), Dominica. 
No. 903. 
The nearest species to this is H. fleruosus, Borzi (J. ¢.), 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 HORMOIDES, Bornet et Flah. (Révis. des Nostoc. 
HHétérocyst. p. 69.) [Seytonema hormoides, Auetz. Sirosiphon 
brevis, Awelz. Botan. Zeit. 1847, p- 196; Tabule phycolog. ii. 
