18 COCCOPHYCE^:. 



Apiocystis Brauniana. Nag. Einz. Alg. p. 69. 



Thallus pear-shaped, pallid green, the cavity filled np by 

 gelatinous matter, in which are imbedded the gonidia, at first 

 few, increasing in number with age, as far as 1600. 



SIZE. Frond '04--1 mm. high, gonidia '012 mm. diam., 

 cells -0075--011 mm. (Rabh.). 



Rabli. Alg. iii. 43. Fresen. Beitr. p. 237, t. ii. f. 1-20. 

 Henfrey in Micro. Journ., 1856, p. 52, t. 4, f. 26-27. 



Fresh water ditches, &c. 



Professor Henfrey found this plant in January, in a jar of water con- 

 taining aquatic plants brought from Wimbledon Common six months 

 previously. The development, as recorded by Nageli, is detailed in the 

 article quoted above. 



"The young 'swarm cells' (zoospores) attach themselves by their 

 ciliated point (especially to Cladophora fracta), and become invested 

 with a club-shaped, enveloping membrane. The first division of the 

 green body then takes place in the direction of the axis of the vesicular 

 envelope, and is repeated alternately in each direction of space. During 

 this the vesicle in which the cells (gonidia) lie, continually expands, and 

 generally becomes very evidently pedunculated. Young vesicles 

 contain a regular number of cells, namely, 2, 4, 8, 16, 32, &c., but the 

 number afterwards becomes indefinite ; in largish vesicles, 1-50'' 

 (*5 mm.) long and 1-120" (-22 mm.) diam. I have counted about 300; 

 in the largest, about 1-25" (*1 mm.) long and 1-50'' (*5 mm.) thick, some 

 1,600 cells. 



" The cells (gonidia) are at first uniformly distributed over the whole 

 cavity of the vesicle. Subsequently they generally become collected on 

 the internal surface of the wall of the vesicle, where they lie in one or 

 more strata. But the cell division always takes place in all directions 

 of space, the cells situated internally advancing outwards towards the 

 periphery. In old vesicles the cells are sometimes arranged in rings 

 of eight upon the wall. When the family of cells is mature for 

 ' swarming,' which may occur at very different sizes and with very 

 different numbers of gonidia, the cells begin to move, at first slowly, 

 from their places, and then gradually to circulate more rapidly in and 

 out about each other ; the vesicle bursts, and the gonidia emerge by the 

 orifice which is formed. Sometimes the swarming is preceded by the 

 state in which the cells are arranged in parietal rings. 



" The cells secrete an abundant gelatinous coating, which becomes 

 softened within the vesicle, and confluent into a structureless jelly. The 

 vesicle sometimes appears merely as the boundary line of the jelly ; in 

 general, however, it may be distinguished as a distinct wall composed of 

 denser gelatinous substance, the internal outline of which is always 

 distinct and sharp, while the outer is frequently indistinct, and partly 

 dissolved." Niigeli, 



Plate VIL Jiff. 1. a, young frond; b and c, older fronds X 100 

 diam. ; d, frond with cells undergoing segmentation X 200; e, part of 

 frond with mature gonidia X 400; f, free gonidia; g, ciliated gonidia or 

 zoospores X 400 diam. 



Inoderma lamellosum, Kutz., has been said to have occurred in 

 Britain, but we have not been able to satisfy ourselves of its occur- 

 rence. 



