1903] Collins, — Notes on Algae 209 
of the Piinia to the almost black Ca/othrix. The honeycombed, 
Symploca-like surface is common to both species, somewhat more 
marked, however, in the Calothrix. Under the microscope the two 
are amply distinct; the Ca/o/Arix with unbranched, tapering fila- 
ments, with no basal layer, the cells of the trichome disk-shaped ; 
the Pinia with branching, nearly cylindrical filaments, cells longer 
than broad, and arising from a basal layer of cells of irregular form. 
The apparent contradiction of the reports of De Toni and Wille, 
both from the original specimens, is easily explained by the manner 
of growth of the Harpswell plant. In Casco Bay the tide has a rise 
and fall of four meters or somewhat more and the ZY/za extends, 
pure or mixed with Ca/o¢hrix, for about a meter ; in the North Sea the 
tide is much less and it is probable that the space occupied by the 
Pilinia would not exceed a few decimeters. ‚Under such circum- 
stances a strip could be peeled off the wood, which would be practi- 
cally pure Piinia at one end, Calothrix at the other. If then 
Wille's specimen came from one end, De Toni's from the other, both 
would be correct in their observations. It is the old story of the 
shield, and the two knights who fought to maintain, one that it was 
silver, the other that it was gold. 
A plant has been distributed as No. 162, Phyc. Bor-Am., under the 
name of Acroblaste Reinschit, which is amply distinct from the Harps- 
well plant. It occurs abundantly at Revere Beach, Mass., on shells 
of Lunatia heros, forming a rich dark green coating about the spire 
of the shell. The coating is uniform with a smooth level surface, the 
upright filaments packed as closely as those of a Ralfsia, quite differ- 
ently from the loosely intertwined Piinia filaments; the latter are 
also more regularly cylindrical, and the basal layer is less of a mem- 
branous character than in Acrod/aste. In the spring months it is 
unusual to find a live Zuzaf£ia without its coating of Acroblaste, and 
the sporangia, like those in Reinsch's figure, are abundant. It has 
not been noticed on empty shells, nor indeed on any substratum other 
than the live shells. //nza, on the other hand, both at Harpswell 
and in Europe, occurs only on woodwork between tide marks. 
Whether the Revere Beach plant is identical with the plant from 
Buzzard's Bay, cannot be absolutely determined; but the latter is 
said to occur abundantly on shells, Turritella in this case, and some- 
times on pebbles. The figures given by Reinsch agree perfectly with 
the Revere Beach plant, and though one who had never seen the lat- 
