172 



Chlorophycece 



their extremities, and often situated each at the apex of a mamillate 

 or obtusely conical protuberance. 



Fig. 65. A and B, Staurastrum anatinum Cooke & Wills, from Llyn-y-cwm-ffynon, 

 N. Wales (x473). C, St. pitnctulatum Breb., from Esher Common, Surrey 

 (x473). D, St. polytrichum Perty, from Galway, Ireland ( x 365). E, St. 

 elowgatum Barker, from Khiconich, Sutherland (x473). F, St. brachiatum 

 Ealfs, from Down, Ireland ( x 473). G, zygospore of St. furcigerum Breb., 

 from Pilmoor, N. Yorks. (x 473). /, front view; v, vertical view. 



There are more than. 160 species of this genus known to occur in the 

 British Islands, but few of them are abundant. The most frequent species in 

 low-lying districts are St. pygmceum Breb., St. punctulatum Breb. (fig. 65 C) 

 and St. hexacerum (Ehrenb.) Wittr. In moorland areas St. margaritaceum 

 (Ehrenb.) Menegh. is general. The most abundant of the spiny species is 

 St. teliferum Ralfs. One of the largest British species of the genus is 

 St. tumidum Breb. (length 112 132 p; breadth 91 103 p.) and the smallest 

 is St. iotanum Wolle. Some species, such as St. capitulum Breb., St. pileolatum 



