STAURASTRUM. 135 



The range of size in this species is considerable, and although 

 it has been customary to specially mention the smaller forms, 

 any line of demarcation is purely arbitrary. The following 

 small form is recorded by many authors, but in some cases it 

 is questionable whether the author who recorded it was aware 

 of the fact that the only basis of separation was " size." 



Forma MINOR Rabenh. Flor. Europ. Algar. Ill, 1868, p. 200; 

 Lund. Desm. Suec. 1871, p. 56 ; Boldt, Siber. Chlorophy. 

 1885, p. 1 10. Pliycastrum depression Nag. Gatt. einzell. Alg. 

 1849, p. 126, t. 8, f. A 1. St. muticum var. minor Wolle, 

 Desm. U. 8. 1884, p. 119, t. 39, f. 14, 15; Hansg. Prodr. 

 Algenn. Bohm. 1888, p. 255 ["var. minus '^ W. & G. S. 

 West, Alg. S. England, 1897, p. 494 ; Alg. N. Ireland, 1902, 

 p. 49 ; ? Cushman in Rhodora, v, 1903, p. 224. St. muticum 

 var. depresxum (Nag.) Nordst. in Pointsf. Skandin. Yaxt. iv, 

 1880, p. 27 ; Schmidle, Beitr. Algenfl. Schwarzwald. u. 

 Rheineb. 1893, p. 109. St. depressum (Nag.) Turn. Freshw. 

 Alg. E. India, 1893, p. 104. 



Cells smaller ; length 16-21 /u breadth 15*5-17 ^t ; breadth 

 of isthmus 4' 5-5 /u. 



ENGLAND. New Forest, Hants ! 



SCOTLAND. Hoy, Orkneys ! 



IRELAND. Near Gleiities, Loughs Machugh and Magrath, 

 Doneo-al ! 



c 



Geogr. Distribution. Germany. Austria. Sweden. Siberia. 

 India. United States. 



Cushman records " St. muticum var. minor Wolle ' from 

 New England with zygospores. He describes these spores as 

 clothed with numerous acute spines, which is a striking con- 

 trast to the zygospore of St. muticum described and figured by 

 Ralfs (consult PL CXVIII, fig. 20). It leads one to suspect 

 that the zygospores observed by Cushman did not belong to 

 the same species as that described by Ralfs. 



7. Staurastrum Bieneanum Rabenh. 

 (PL CXX, figs. 4-6.) 



Staurastrum Bieneanum, Rabenh. Alg. Eur. 1862, no. 1410; Wittr. & 

 Nordst. Alg. Exsic. 1877, no. 73; be Toni, Syll. Alg. 1889, p. 1197; 

 West, Alg. W. Ireland, 1892, p. 177 ; Alg. Engl. Lake Distr. 1892, 

 p. 731 ; Roy & Biss. Scott. Desm. 1893, p. 178 (sep. p. 17) ; W. & G. S. 

 West, Alg. Madag. 1895, p. 74 ; New and Int. Freshw. Alg. 1896, p. 158, 

 t. 3, f . 27 ; Nordst. Index Desm. 1896, p. 58 ; W. & G-. S. West, Alg. S. 

 England 1897, p. 494; Alga-fl. Yorks, 1901, p. 101; Alg. N. Ireland, 1902, 

 p. 49 ; Freshw. Alg. Orkneys and Shetlands, 1905, p. 25 ; Further 

 Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 486 ; Comp. Study 



