292 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



6. On shells, pebbles, etc.; sporangia on erect filaments. 



4. P. Reinschii. 



6. On woodwork ; sporangia on basal layer, rarely lateral on erect 

 filaments. 6. P. Morsei. 



1. P. LUNATIAE Collins, 1908, p. 123, PI. LXXVII, figs. 

 1-3; Acroblaste Reinschii P. B.-A., No. 162. Basal filaments 

 soon becoming united into a subparenchymatous layer, cells of 

 varying shape and size, roundish or angular, up to 15 /* diam.; 

 erect filaments 8-12 p. diam., increasing in size upward, usually 

 5-6 cells in length, quite rarely up to 10 cells, densely branched 

 and very compact, cells varying in size and shape in the same 

 filament ; terminal cell becoming the sporangium, differing but 

 little from any other cell of the filament ; color deep green. On 

 live shells of Lunatia heros Adams. Mass. 



Very common on Lunatia shells at Revere Beach, Mass., but 

 not reported elsewhere. It forms a very deep rich green coating 

 at the flat spiral of the shell, but on living shells only. The 

 substance is very compact, the filamentous character being made 

 out with difficulty. The spores are produced in the terminal 

 cells of the upright filaments, slightly enlarged, but not other- 

 wise changed. It is a plant of spring and early summer chiefly. 



2. P. MINOR Hansgirg in Foslie, 1890, p. 146, PI. II, 

 figs. 17-22. Stratum thin-coriaceous or almost crustaceous, 

 yellow-green, more or less extended ; basal layer dense, indi- 

 vidual filaments indistinguishable ; erect filaments irregular, 

 vertical or inclined, as small as 2 /u. diam. at the base, increas- 

 ing in size upward to as much as 7 yn at the summit ; not much 

 branched. Sporangia terminal, pyriform but rather irregular, 

 20-24 X 10- 12 //.. On pebbles by the seashore. Mass. 



Northern Europe. 



The distinction between the basal and the erect filaments is 

 less than in P. Limatiae, but the sporangia are more clearly dif- 

 ferentiated. In the onjy recorded American locality, it grew on 

 pebbles between high and low tide marks, and when the tide 

 was out was wet with cold water from a spring. 



3. P. ENDOPHYTICA Collins, igoSc, p. 156. Frond of no 

 definite form, consisting of usually short, simple or branched 

 filaments, creeping among the filaments of the host ; cells vari- 

 able in form and size, cylindrical, clavate, subspherical or 

 irregular, 7-22 p. diam., 1-5 diam. long; chromatophore light 

 green, sometimes filling the cell, more commonly cup-shaped, 

 at the upper end of the cell. Sporangia terminal, spherical or 



