Mr. J. Ralfs on the Nostochinec. 327 
Tricnormus, Ad/man. 
Filaments simple, moniliform, distinctly jointed, aggregated into 
an indeterminate gelatinous stratum ; sporangia separated from 
the vesicular cells by the ordinary joints, which they more or 
less resemble in form. 
(Anabaina, Bory, Brébisson, Kiitzing, Montagne and others.) 
In Trichormus the stratum is indeterminate and very gela- 
tinous ; at first it is nearly colourless and transparent, and the 
filaments are only sparingly scattered through the matrix ; but 
the filaments rapidly increase in number, and the mass, gra- 
dually becoming more opake, acquires at length a deep bluish 
green colour, which is occasionally mottled with brown, especially 
beneath. 
The filaments are mostly short, distinctly moniliform, and fre- 
quently as much curved as those of a Nostoc. The cells are all 
more or less orbicular, and the sporangia differ less from the 
ordinary cells than they do in the following genera. Viewed 
under the microscope the filaments scarcely differ from those of 
a Nostoc. In both genera they are usually curled, their cells are 
orbicular, the vesicular ones are interstitial and terminal, and the 
sporangia are often uot apparent, or are known only by their 
denser endochromes. 
In some of the aquatic species the stratum separates into large 
floating gelatinous masses, and then can only be distinguished 
from Nostoc by the gelatinous portions having no definite form 
or size, and by the absence of an epidermis. 
Professor Kiitzing refers Monormia intricata, Berk., to this 
genus. I have never gathered that plant, and I was unable to 
determine the genus from recent specimens sent me by Mr. 
Thwaites from Bristol ; but, judging from Mr. Berkeley’s figures 
and description, I should suppose that the more definite frond 
and the elongated, solitary and peculiarly convoluted filament 
are sufficient to sustain the genus. 
As Professor Harvey has reminded us in his ‘ Phycologia Bri- 
- tannica’ that Bory’s name Anabaina has been appropriated to a 
genus of flowering plants, and it becomes necessary to choose 
another, L have adopted Professor Allman’s name Trichormus as 
next in priority. 
Trichormus differs from Dolichospermum in its sporangia, which 
are more or less orbicular, and from Spherozyga and C ylindro- 
spermum by the different arrangement of the sporangia and vesi- 
cular cells. 
1. T. Flos-aque (Lyngbye). Filaments flexuose or curved, monili- 
form ; cells orbicular, vesicular ones larger, terminal and interstitial. 
Nostoe Flos-aque, Lyngbye, Tentamen Hydrophytologiz Danicee, 
