sulphureous properties, as if the hepatic gas were necessary
to its production and nourishment.” — Dillw.
5. T o ly p o th k ix r u f e s c e n s .
Plate L X IX . Fig. 7.
Char. Filaments minute, spreading in a thin slimy purplish
stratum.
Calothrix rufescens Carm.; Harv. in Hook. B. Flor. p. 368.;
Harv. in Manual, p. 158.
Ilab. On rocks under the spray of cascades, Appin: Cap-
tain Carmichael.
“ Crust or stratum of indefinite extent, and so thin as to
seem a mere discoloration of the rocks until the finger is
passed over it, when a certain sliminess detects the presence
of the plant. Filaments half a line in length, and so slender
as to appear mere lines under the highest power of the compound
microscope.”— Carm. M S .
b. Branches adherent to the main filaments.
6. T olypothrix D illwynii Hass.
Plate L X V I I I . Figs. 4, 5.
Char. Filaments tufted. Branches subulate, adherent to the
principal threads nearly their whole length. Striæ about
a diameter from each other.
Scytonema Dillwynii Harv. et Ralfs’ MS.
Hab. Dolgelly : Mr. Ralfs. Moist rocks, co. Antrim :
3Ir. Moore.
This species was named by Harvey Scytonema Dillwynii,
under the impression that it was the Microcoleus ? Dillwynii
of his “ Manual,” and the Conf. vaginata of Dillwyn, t. 99.
which it is difficult to conceive from Dillwyn’s description
tha t it really is. I felt much inclined to place this plant by
243
itself m a distinct genus, and perhaps this would have been
the correct course; it is, however, more naturally associated
with the genus Tolypothrix than with Scytonema. I t forms
little tufts two or three lines in height.
28. C A L O T H R IX .
Char. Filaments o f equal diameter, branched by apposition.
Derivation. From uabas, beautiful, and 0pi^, a hair.
1. Calothrix mirabilis.
Plate L X IX . Fig. 1.
Char. ^ Filaments tufted, ceruginous, black, articulated. Striæ
distant about the h a lf o f a diameter from each other, distinct.
Conf mirabilis DiUw. t. 96. Calothrix atroviridis Harv.
^ in Manual, p. 159. ; Harv. in Hook. B. Flora, p. 369.
Hab. ^ On mosses and in small streams, rare. Stream
which runs through the wood at PenUegare, near
Swansea: Dillwyn. — C. atroviridis in spring wells, near
Penzance : Mr. Ralfs. Aberdeen : Dr. Dickie.
Having had opportunities of examining, through the kind-
:^ss of Mr. Dillwyn and Mr. Harvey, authentic specimens of
Conf mirabilis and Calothrix atroviridis, I have no hesitation
in declaring th a t the two plants are identical. There
IS a close resemblance between C. mirabilis and Lyngbya
copulata, which species ought not to be far removed from each
other in a natural arrangement.