10 Transactions of the Society. 



been detected in this country only once before, by Henfrey, as long ago 

 as 1856, at Wimbledon. My observations agree nearly with the descrip- 

 tions of Niigeli and Cooke, but I was not fortunate in having the mode 

 of reproduction under view The " frond " was irregularly pear-shaped, 

 with well-defined outline, 275 [jl long by 165 yu, broad (including stalk), 

 the stalk 62*5 fi long by 25 /a broad. The " gonidia " or green 

 pseudo-cells appeared to be arranged in a parietal layer, some of them 

 in pairs as if they had undergone recent division, moderately crowded 

 towards the apex of the " frond," fewer towards the base, entirely 

 wanting in the stalk. They were bright green, round or slightly oval, 

 about 17 yu. in diameter or less. 



*DictyosphaBrium Ehrenbergianum Nag. 



Bog pool, IMawgan. In the specimens observed the reniform pseudo- 

 cells were united together in pairs or threes by a slender thread ; the 

 whole colony was moving rapidly through the water, but was not in- 

 closed in hyaline gelatin. 



In the same pool was observed what is probably an undescribed 

 species of the same genus ; the cells much smaller and spherical, and 

 united together irregularly in bunches. 



*Hydrianum heteromorphum Keinsch. Fig. 2. 



Attached to a Mesocarpus in a bog pool, Mawgan. Cells about 19 /u, 

 long by 10 /i broad, observed both closed and open, filled with a light 

 brown endochrome. 



Chroococoaoe^. 



Chroococcus turgidus Nag. 

 *Gloeocapsa polydermatica Ktz. On wet rocks, Boscastle. 



Aphanocapsa virescens IJabh. 



Microcystis marginata Kirchn. 

 *Coelosph8erium Ktitzingianum Nag. 



Very common in bog pools. The "frond" may be nearly spherical 

 or 2-3-lobed, always studded with pale blue-greeii projections. When 

 2-lobed, and the lobes nearly equal in size, it might readily, but for 

 its blueish-green colour, be mistaken for a Cosmarium. 



Merismopedia glauca Nag. 

 * Aphanotfiece microscopica Nag. (Gatt. Einzell. Algen, p. 59, 

 t. i. H. f. 1). Fig. 3. 

 Not uncommon in bog pools. Thallus irregularly oval, outline lobed 

 or sinuous, about 650 /x long by 325 yu, broad, perfectly colourless and 

 hyaline. " Gonidia " or pseudo-cells narrowly elliptical, 25-40 //. long, 

 4-5 times as long as broad, somewhat pointed at both ends and usually 

 divided or constricted in the middle, sparingly and nearly uniformly 

 scattered through the thallus. Contents of pseudo-cells very pale_ blue- 

 green. Differs from both the species described by Cooke as British in 

 the thallus being colourless instead of blue-green, as well as in other 

 points. First described by Ntigeli from Zurich ; Eabeuhorst speaks of 

 it as abundant in Germany. 



