PDF file (text) - Cryptogamic Botany Company

REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 37
easily distinguished under the microscope, C. confervicola being darker colored, the filaments thicker,
and only furnished with heterocysts at the base, whereas in C. crustacea the heterocysts are scattered
through the filament, often solitary, but sometimes as many as eight together, and frequently truncate.
C. crustacea is also common on rocks.
b. Species forming expansions.
C. SCOPULORUM, Ag.‚ Phyc. Brit., Pl. 58 b; Ner. Am. Bor., Part III, p. 105.
Filaments forming strata of indefinite extent, flexuous, usually branching, .008-12 mm
in diameter, heterocysts basal and intercalary, sheaths thick, striate.
Var. VIVIPARA. (C. vivipara, Harv., Ner. Am. Bor., Part III, p. 106.)
Nahant, Wood’s Holl, Mass., W. G. F.; Rhode Island, Bailey; Europe. Var. vivipara at
Nahant, W. G. F., and Seaconnet Point, Bailey.
Forming indefinite-shaped patches on rocks, on Rhizoclonium, and other prostrate algæ. Apparently
much less common than the two preceding species. It differs from C. crustacea in the flexuous habit of
the filaments, which are loosely twisted around one another, in the much rarer occurrence of
intercalary heterocysts, and in the color of the filaments, which is not a bright green, but generally
brownish. The sheaths, too, become thick, dark, and striated. As is the casein all species of Calothrix
where the filaments are closely interwoven, the diameter of the filaments is greater and that of the
sheath less, proceeding from within outwards. The variety vivipara is only a luxuriant form of the
typical species.
C. PULVINATA, Ag. (C. hydnoides, Harv.)
Filaments densely packed, forming a dark green spongy layer, united at the surface
in tooth-like masses, flexuous, .006 mm to .0115 mm in diameter, heterocysts
intercalary.
Exs.—Alg. Am. Bor., Farlow, Anderson & Eaton, No. 50.
Wood’s Holl, on wharves. Common. Europe.
In this species the filaments are much more densely interwoven and flexuous than in any of the
preceding species. It forms patches looking like a honeycomb, or like a small Hydnum, and can be torn
from its attachment in pieces of considerable size.
C. PARASITICA, Thuret. (Rivularia, Chauvin.—Schizosiphon, Le Jolis.) Filaments
loosely united, forming a velvety film, bulbous at base, simple or only slightly
branching, about .008-10 mm in diameter, heterocysts basal, obliquely truncate.
On Nemalion multifidum, Newport, R. I.; Europe.
Easily recognized by its bulbous base and obliquely truncate heterocysts, and its peculiar habitat.
RIVULARIA, Roth.
(Named from the fluviatile habitat of many of the species.)
Frond gelatinous, more or less globose, filaments radiating, attenuated, furnished
with distinct sheaths, branching, a heterocyst at the base of each branch.