54 BRITISH DESMIDIACE^E. 



Zygospore of t}^pe unknown.* 



Length, without spines, 48-67 (JL ; with spines, 54-80 [A; 

 breadth, without spines, 41-48 [JL ; with spines, 50-70 (JL ; 

 breadth of isthmus 15-22 [i ; length of spines 5-11 [i ; 

 diam. zygosp. (var.) without spines, 53 ^ ; with spines,. 

 78 pi. 



ENGLAND.- -Westmoreland ! (Biss.). W. andN. Yorksf 

 Warwicks ! Surrey ! Hants ! Devon (Bennett, Harris). 

 Cornwall (Bennett). 



WALES.- -Llyn Padarn, Llyn Idwal, Llyn Gfwynant, 

 Capel Curig ! (Cooke & Witts) and Snowdon (Roy), Car- 

 narvonshire ! 



SCOTLAND.- -Eoss, Inverness, Aberdeen, Kincardine, 

 Forfar, Perth !, Argyle, Wigtown (Roy & Biss.). Plank- 

 ton of Loch Shin, Sutherland ! 



IRELAND.- -Lough Anna, Donegal ! Clare Island, Co. 

 Mayo ! Small lakes, Clifden to Roundstone, Co. Galway ! 

 Cloonee Lough, Co. Kerry ! Dublin and Wicklow (Arch.). 

 Stream, N. of Newcastle, Co. Down ! 



Geogr. Distribution. Germany. Switzerland. Galicia 

 and Austria. Norway. Sweden. Finland. S. Russia. 

 India. United States. N. W. Canada. Argentine. 



This species is one of the most beautiful of the spiny Staurastra. 

 It is distinguished from St. gladiosum Turn, by its greater size 

 and relatively greater length, and by the uniform character 

 and regular arrangement of its more numerous spines. 



80. Staurastrum Saxonicum Bulnh. 

 (PL CXXXVII, fig. 7.) 



Staurastrnin sp. Bulnh. Einige Desm. 1859, p. 22, t. 2, f. 7. 



St. Saxonicum Bulnh. in Rabenh. Krypt.-flor. Sachs. 1863, p. 190 ; Rabeiih. 



Flor. Europ. Alg. 1868, p. 213 ; Nordst. Desm. Spetsb. 1872, p. 40 ; Desm. 



Arct, 1875, p. 35 ; Boldt, Desm. Gionland, 1888, p. 36; De Toni, Syll. 



Alg. 1889, p. 1173 ; Borg. Desm. Brasil, 1890, p. 949 ; Roy & Biss. Scott. 



Desm. 1893, p. 25, t. 3, f. 10 ; West & G. S. West, Alg. S. England, 1897, 



p. 494 : Alga-fl. Yorks. 1902, p. 99 ; Cushman in Rhodora, 1903, p. 222. 



The zygospore of St. polytrichum var. readingense Cushman has been 

 described in 'Bull. Torr. Bot. Club,' 1905, p. 228. In general form it is 

 spherical, and it is thickly beset with peculiar spines which are very broad at 

 the base ; at the apex they are first trifurcate and then bifid. The whole zygo- 

 spore including the spines is thickly covered \vith irregular elongated granules. 

 It is a very extraordinary zygospore (see PL CXXXVI, f. 11). 



