NEW OK CRITICAL BRITISH ALG2E. 
53 
below, incurved above, the outer margins strongly biserrate, ultimate 
serrations thorn-like ; conceptacles marginal, solitary, sessile ; 
tetraspores zonate on decompound dichotomous processes with 
bifid apices. 
The plant should be carefully sought for on the Southern Coasts 
of England and Ireland, where it may have been mistaken for a 
very broad form of Pl. coccineum. In general appearance the 
plant more resembles some of the species from Australia or the 
Cape of Good Hope than our only British species. 
Melobesia callithamnioides, FalTcbg., Alg. Neap. p. 265 . 
Weymouth. On Viva lactuca. Sept. 
Thallus very thin, adhering with the entire under-surface to the 
substance on which it grows, consisting of irregularly dichotomous, 
radiating, articulated threads 10-20 p, in diameter; filaments either 
remaining free and branching in an irregular dichotomous manner, 
often anastomosing, or united into flat fan-shaped or roundish 
expansions. Cells shorter than to one-and-a-half times as 
long as broad, with a very minute and indistinct cortical cell on 
the upper anterior margin of each. Besides the ordinary cells of 
the thallus, a second kind of cell, distinguished from the others 
by its larger size, convex apex, and the absence of the cortical cell, 
is present in this species. Conceptacles, large and numerous 
formed on the fan-shaped expansions. 
This species forms a very indistinct pink stain on the surface of 
the host plant, and when growing on thick coarse algae is very 
difficult to detect, but when on membranous translucent plants 
such as Nitophylla and Ulvce it may at once, owing to the 
opaqueness of the chalk granules, be seen forming a dark patch on 
the fronds of the host plant. Hauck supposed that this species 
may be only a form of Melobesia farinosa , Lamour, but if so it is, 
in my opinion, a very distinct one. There can be little doubt that 
Hapalidium callithamnioides , Crouan, is identical with the present 
species, although, as Hauck points out, the figure in the “ Florule 
du Finistere ” is very incorrect. 
Bibliography. 
A New Perforating Alga. — MM. J. Huber and F. Jardin 
(Journ. Botanique, Morot, Aug., 1892) find on the shells of 
species of Helix and also on calcareous stones in clear rapid streams 
near Montpellier, a new fresh water perforating algae, which they 
have called Hyella fontana. This new species, which is beautifully 
figured by the authors, agrees with Hyella ccespitosa, Born, et Flah., 
in its mode of growth, in the faculty it possesses of forming 
sporangia and of assuming the appearance of a chroococcaceous 
alga, but differs from it in possessing a non-septate sheath, each cell 
having a cell-wall, and the simplicity of the sporangia, which, in 
some respects, show an approach to the genus Pleurocapsa. 
