STAUEASTRUM. 141 



WALES. Capel Curig, Carnarvonshire (OooJce 



Wills). 



SCOTLAND.- -Locli Shin, and plankton of L. nan 

 Cuinne, Sutherland ! Near Locli Mharc in the forest 

 of Athole, Perth (Roy Bissett). Plankton of Loch 

 Doon, Ayr ! ; Lochs Cuthaig and Fadaghoda, Lewis ! ; 

 Loch nan Eun, N. Uist ! ; and Loch Laxadale, 

 Harris ! 



IRELAND.- -Rare in the plankton of the small lakes 

 between Clifden and Roundstone, Galway ! 



Geoyr. Distribution.- -Germany. Austria. Sweden. 

 United States. Brazil. Australia. 



St. grande is a rare Desmid, which we have chiefly met 

 with in the plankton of the western lake-areas. The form of 

 the semicells is somewhat variable, some having a much less 

 convex dorsal margin than others. The relative length and 

 breadth of the cells is also slightly variable, and some 

 individuals have more rounded angles than others. 



The zygospores have been observed by C ashman from 

 Reading, Mass., U.S.A. This author also describes a var. 

 glabntm in which the cell-wall is perfectly smooth. Moreover, 

 the zygospores of this smooth variety are not so angular as 

 those of the type, and are "more densely set with shorter and 

 more slender spines." 



The disposition of the chloroplasts in Si. grande is subject 

 to much variation. Lundell, who was the first to examine 

 them with care, described and figured them as parietal 

 masses. Dr. Liitkemuller, who has recently made a careful 

 study of them in large numbers of individuals, finds all con- 

 ditions from truly axile to truly parietal chloroplasts, and 

 states that the former condition is the more prevalent. 



Var. parvum West. (PL CXX, figs. 2, 3.) 



St. grande var. parvum West, New Brit. Fresh \v. Alg. 1894, p. 11, t. 2, 

 f. 51 \= St. brevispinum Breb. var. inerme Wolle, Freshw. Alo\ U. S. 

 1887, t. 62, f. 9, 10 (non Wille, 1879). J 



Cells smaller, with a narrower isthmus ; angles of 

 semicells more rounded. Cell-wall finely punctate. 



Length 61-63 /x; breadth 60-61 //, ; breadth of 

 isthmus 13*5-14 p.. 



SCOTLAND. Grlen Shee, Perthshire ! 



