r
320 rR O T O C O C C EÆ . HÆ M A TO C O C C U S . 321
»1
1. B otridina tulgaris Breh. in lit.
Plate L X X X I . Fig. 2.
Char. “ Fronds small, spherical, aggregated, often confluent,
green, solid, with minute globose or subangular globides.
“ Nostoc botryoides Ag., Syn. p. 135. Palmella botryoides
Lyno-., Hydrop. p. 205. No. 6.; Ag. Syst. p. 14. No. 5.;
g L v . Scot. Crypt. Fl. t. 5. No. 243. ? P. Grevillei
Berk., Glean, vol. i. p. 16. t. 5. f. I . - V ’ - Meneghmi.
Botridina vulgaris Meneghini, in Monograph. Nosto-
chinearum.
“ The fronds of various sizes, rarely surpassing the head
of a p in f df a subspherical form, aggregated in considerable
quantity, cover the stems of mosses with a pulverulent
blackish green stratum, which Agardh first well delin^ted.
The granules in the beginning solitary, here and there athxe
subspherical or slightly angular, scarcely equal m their
greatest diameter the five hundredth part of a millimetee ;
gradually they increase in size, and when they have arrive
at the two hundredth part of a millimetre, they manifes.t an
internal granular substance; at a later period having acquired
a form exactly spherical, the internal substance is seen aggregated
or collected into the centre, and the granules surrounded
by a peUucid margin. Again they increase in size, and
the interior granules are seen converted into vesicles filled with
lesser granules. These vesicles increased m number and magnitude,
the greatest dimensions of the frond being attained,
occupy its entire substance, and at length the diaphanous
marrin disappears. The whole frond is then constituted ot
vesicles closely heaped together, and enclosing m the centre
granules. The primitive membrane, enclosing m its midst
the interwoven or cellular structure, is so closely united with
the peripheral stratum of vesicles, th a t it can m no way be
separated from it. The last developement having been accomplished,
the peripheral stratum of vesicles altogether looses
its granules : whether these disappear by absorption, or escape
outwardly, I have never been able to perceive. In this manner
the frond again obtains a diaphanous margin, hut different
from that with which in the beginning it was surrounded.”—
Menegh.
49. H iEM A TO C O C CU S Ag.
Char. ^ Cells spherical or oval, o f various sizes, each invested
with one or more concentric vesicles or membranes, multiplied
either by division or by granules formed within the
parent cells.
Derivation. From a i g a , hlood, and k o k k o s , a berry.
Agardh has evidently included in his genus Hcematococcus
productions generically distinct; as, for example, H .^ ig u in e u s
and HcEm. or properly Protococcus nivalis : he therefore would
appear not to have entertained any precise ideas In reference
to his genus beyond the fact of the contents of the cells of
some of the species being of a red colour. Meneghini in the
memoir so often referred to, limits the genus Hcematococcus
to one species, the H. nivalis of Agardh, a production which
assuredly does not difier even specifically from the Protococcus
nivalis of the same author, and constitutes a new genus
Microcystis for the reception of H. sanguineus and its allies,
the adoption of which, as H. nivalis Ag. cannot be allowed
to remain in tha t genus, is rendered unnecessary.
Of the two terms Hcematococcus and Alicrocystis, the latter
is by far the more applicable, the former being in some degree
objectionable, inasmuch as it is founded on the colour of
the globules, a colour confined to a limited number of the
species of the genus. Meneghini thus defines his genus
Microcystis : —
“ Frond mucous ; in the beginning definite, at a later period
etfused, including globules clothed in vesicles and multiplied
by a quaternary division or by granules evolved
within, constituting so many new fronds.”
“ Each globule, in the same way as those of the Pleurococci,
shrinks from its involucre, and then appears to be clothed
with its proper vesicle. A process of this kind is frequently