ADDENDA. 263 



of the inner margin nearly straight, or even slightly 

 concave, cells 138-175 of arc. 



Length 137-172 JJL ; breadth 18*3-25 (j.. 



IRELAND.- Near Dugort, Achill Isle ; near Louis- 

 hurgh ; Doo Lough and near Westport, Mayo ! 



Closterium tumidum Johns, (vol. i, p. 156). 

 Var. sphserospora West (PI. CLXVI, figs. 8. 9). 



('I. fnniiiliiiii var. *jifi(rr<i*iK>r<i ('. S. West in Journ. Bot. 1911, p. 84, f. 1. 



A variety Avith short, thick cells. 



V 



Zygospore subglobose or ellipsoid-globose. 

 Length 48-66 [JL ; breadth 8-8'oa ; breadth of apex 

 3-4 IL : diam. zvo'osj). J3 < 5-26u. 



* ' i. 



KXCLAND. -Earlswood, Warwickshire ! 



This variety is distinguished from the typical form of Cl. 

 i tun i<l urn by its smaller and stouter cells, and the zygospore is 

 rounded, instead of rectangular with produced angles and retuse 



margins. 



Closterium Cornu Ehr. (vol. i, p. 157). 

 Yar. arcum West. 



<'l. Cornu var. un-nni West, Clare Isl. Alg. 1912, p. 11. 



Cells more strongly curved than in the type, up to 

 85 of arc, margins only parallel in the middle. 

 Length 138{/. ; breadth S'OJJL. 

 IRELAND.- -Lough Gall, Achill Isle. Mayo ! 



Closterium toxon West (vol. i, p. 160). 

 Var. validum West. 



<'l. toxon var. valid H in West, Clare Isle Alg. 1912, p. 13, t. 1, f. G. 



Cells twice as thick as in the typical form. 

 Length 250-260 u ; breadth 17'5-20jJt. 

 IRELAND. Clare Isle, Mayo ! 



