Ulotrichacece 



I I 



8 



9 



B 





that the filaments often consisted of a double row of cells. Wolle seems 

 to have observed the same plant from several parts of the United States 

 (cf. Freshw. Alg. of U. S. t. cxxv). 



Genus Hormospora Breb., 1840. The filaments are simple 

 and free-floating, rarely fixed by a mucous disc, and they consist of 

 a single series of cells embedded 

 in a thick, cylindrical, mucous in- 

 vestment. This outer gelatinous 

 coat varies in its relative size, 

 and is always hyaline and homo- 

 geneous. The cells are commonly 

 oblong-cylindrical with broadly- 

 rounded extremities, and they 

 contain a single parietal chloro- 

 plast usually disposed as an 

 equatorial band. One pyrenoid 

 is generally present in each chlo- 

 roplast, although rarely pyrenoids 

 are quite absent. The genus is 

 very closely allied to Ulothrix, 

 but is distinguished by its thick 

 gelatinous coat and by the con- 

 stant separation of the cells after 

 division. Cienkowski and others 

 have regarded the genus as a mere 

 state or condition of Ulothrix, but 

 I think that is open to much doubt. The cell-wall is extremely thin 

 and delicate, and the formation of zoogonidia has not been observed. 



The most frequent British species is H. mutabilis Breb. (fig. 22 A), which 

 occurs principally in bogs, especially amongst Sphagnum, and in such 

 localities species of Ulothrix do not usually exist. The cells are 16 19 p 

 in diameter and \\ If times longer than broad. H. ordinata West & 

 G. S. West (fig. 22 B) is a smaller and much rarer species with cells 5 -8 p. in 

 diameter. H. plena Breb. is the only other British species. 



Genus Glceotila Kutz., 1843. This is a genus of small Alga 1 

 intermediate in character between Hormospora and Ulothrix. 

 The cells are very small, oblong or elliptical and more or less 

 moniliform, but they are not so completely separated as those of 

 Hormospora ; they are arranged in a single series in a delicate 

 mucous envelope, and each one contains a parietal chloroplast 

 of small size which is disposed as in Hormospjra. I have not 



Fig. 22. A, Hormospora mutaliUix 

 Breb., from near Mullion, Cornwall. 

 B, H. ordinata West & G. S. West, 

 from Cam Fell, W. Yorkshire. C E, 

 Glceotiln protofieiiita Kutz., from Pil- 

 moor, N. Yorkshire. ( x 440.) 



