336 Mr. J. Ralfs on the Nostochinee. 
night, rays an inch or more in length. Filaments elongated, 
comparatively stout, visible to the naked eye, under the lens full 
green when grouped, but bluish green when scattered. Ordi- 
nary joits orbicular. Vesicular cells elliptic, broader than the 
ordinary ones. Sporangia near the middle of each series of 
ordinary joints, most frequently solitary, rarely more than two 
together, at first oval, afterwards oblong, finally cylindrical, and 
about six times longer than broad. In their early state they 
resemble the vesicular cells in form ; but the presence of granular 
matter and the absence of junction-globules reveal their true 
character : the longer ones are frequently contracted at the mid- 
dle, a circumstance I have occasionally noticed in those species 
which have elongated sporangia. 
Dolichospermum Ralfsii is distmguished from D. inequale by 
its elliptic vesicular cells (which are comparatively less broad), by 
its more orbicular ordinary joints and by having fewer sporangia. 
PuaTeE IX. fig. 2. 
3. D. Thompsoni ( ). Filaments spirally curved ; ordinary and 
vesicular cells spherical ; sporangia oblong, curved, usually solitary. 
Anabaina Flos-aque, Harvey, Manual of Brit. Algze, p.186 (1841); 
Hassall, British Freshwater Algee, p. 282. t. 75. fig. 2. 
* Floating like powdered verdigris on one of the small Lochs Ma- 
ben, Dumfries-shire,”’’ Mr. W. Thompson. 
A specimen of this plant, given me by Mr. Thompson, forms 
on paper a thin stain of a bluish green colour. Filaments mo- 
niliform and loosely spiral. Ordinary and vesicular cells orbi- 
cular, and so much alike in form and size that in the dried state 
I am unable, with absolute certainty, to distinguish the latter 
from ordinary cells which have lost their granular matter. Mr. 
Thwaites however informs me, that by a careful adjustment of 
the lens, he has detected the puncta in the vesicular cell, in which 
also he finds the membrane firmer than in the others. Sporangia 
solitary (rarely two together) in each series, two or three times 
longer than broad, curved, so as to appear somewhat reniform, 
and more rounded at their ends than is usual in this genus. 
This species is easily distinguished from the others by its 
curved filament and reniform sporangia. Its moniliform, spiral 
filament agrees better with Trichormus than with Dolichospermum, 
but in its elongated sporangia it differs from every species of the 
former. 
Puate IX. fig. 3. 
4, D. Smithii* (Thwaites MS.). Filaments straight, each included in 
* For the description of this and the following species I am indebted to 
Mr. Thwaites. 
