F am. X IV . R IV Ü L A K EÆ .
Char. Frond usually gelatinous, lubricous, and definite, in
which are embedded idwaQ'siis often fla g elliform, simple, or
spuriously branched, hilted below, the hilts being formed
o f an enlarged cell, connected to the filaments by a narrow
neck, and filled with endochrome. Sheaths in which the
filaments are enclosed, sometimes saccate beloio, above attenuated
and open.
No very exact observations have as yet been made upon
the reproduction of this family. Do not the enlarged cells
which terminate the base of the filaments correspond in
function with those of the Nostochineoe ? In the setigerous
elongation of the filaments a resemblance to Choetophora is
manifested. Certain species exhibit a relation to the Scytonemea.
31. R IV U L A R IA .
Section i. R iv u l a r ia Roth.
Char. Yroriàwart-shaped, rarely encrusting, coriaceous. Filaments
close, set firmly, adherent, spuriously branched,
radiating.
Linhia Lyngb.
1. R iv u la r ia P isum Ag.
Char. Frond globose, smooth, shining, dark green. Filaments
dichotomous, firm ly united.
Harv. in Hook. Br. Fl. vol. ii. p. 392. ; Berk., Glean. Alg.
t. 2. p . 2.
Hab. On aquatic plants in subalpine streamlets, Appin:
Captain Carmichael. Cheshunt Common : A. H. H.
%
“Fronds a line in diameter, scattered or confiuent, of a dark
green colour and fieshy firmness. Filaments radiating from
the base, dichotomously branched and alternate, the apices
free.” — Carm. I have no hesitation in referring all the
British specimens which I have seen of this species to Rivularia
botryoides, and these again to R. granulifera, which species
I consider R. Pisum to be in the earliest period of its
developement, and Rivularia botryoides that species in the
middle period of its growth.
The following is Carmichael’s description of R. botryoides,
which, like the preceding, is found attached to stones, &c., in
streamlets.
“ Fronds about a line in diameter, hemispherical, wrinkled
and cartilaginous, scattered or running together like a bunch
of grapes. Filaments cohering firmly, obscurely striated,
dichotomous. Colour, when fresh, black; on drying, darkly
ferruginous.” — Carm.
2. R iv u la r ia g r a n u l if e r a Carm.
Plate L X V . Figs. 1. 4.
Char. Frond large, convex, becoming hollow underneath,
fleshy, lubricous, brownish olive, often including stony
particles, never petrified. Filaments slender, firm ly adherent,
furnished with a broad sheath.
Harv. in Hook. Br. Fl. p. 393.; in Manual, p. 151.
Hab. On cliffs exposed to the trickling of water, common,
annual, A p p in : Captain Carmichael. — Yax. botryoides
in streamlets, attached to rocks and stones, co. A n trim :
Mr. Moore.
“ Fronds from a line to half an inch in diameter, often confiuent,
convex, and at length concave underneath, fieshy,
dusky olive green, and extremely slippery. Filaments rather
thick, repeatedly dichotomous. In the substance are generally
enclosed a number of stony particles. This species
comes nearest in size and form to R. calcarea, but is never
like that petrified with calcareous m a tte r; and it is moreover
s 4