172 



CMorophycece 



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-cwui-ffynon, 

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

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

 eloiigatiim Barker, from Bhiconich, Sutherland (x473). F, St. brachiatum 

 Half's, from Down, Ireland ( x 473). G, zygospore of St. furciijeniin Breb., 

 from Pilmoor, N. Yorks. (x473). /, front view; v, vertical view. 



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

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

 low-lying districts are St. pygmceuiii 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 ^; breadth 91 103 p.) and the smallest 

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



