50 BRITISH DESMIDIACEjE. 



Length 97-123 /i; breadth 26-30 /u. 

 IRELAND. Mourne Mts., Down. 



This form occurred in gelatinous masses on rocks, 

 with other Desmids and numerous Diatoms. Many of the 

 individuals were straight, the others being slightly curved. 



Forma tennis forma nov. (PL Ill, fig. 22.) 



Cells rather narrower than in the typical form ; a 

 little more than 5 times longer than their diameter. 

 Length 83 /u ; breadth 15*5 /u. 

 ENGLAND. Epping Forest, Essex ! 



This form occurred in peaty ditches along with Euastrum 

 lobulatum and Tetntemonis granulatus. It is of about the 

 same length as the type, but is proportionately narrower. 

 The cells were embedded m a mass of mucus produced princi- 

 pally by numerous specimens of Varikeurckia rhomboides var. 

 Saxonica. 



Var. breve West. (PL III, fig. 20.) 



M. DC Greyi var. breve West, Alg. W. Ireland, 1892, p. 131, t. 20, t'. 0. 



Cells almost straight or slightly curved, 2^ times 

 longer than their diameter. 



Length 58 p ; breadth 2 1 -22 /u. 



IRELAND.- -Tore Mountain, Kerry ! , on dripping rocks 

 with Ampho ridium Mongeotii and other mosses. 



The cells of this variety are much shorter than those of the 

 type, but in their breadth and other respects they are pre- 

 cisely similar. 



2. Mesotaenium mirificum Arch. 

 (PL IV, figs. 18, 19.) 



Mesotxnium mirificum Arch. PalmogloBa and descrip. Mesot. 1864, p. 19, 

 t. 1, f. 20-31 ; Cooke, Brit. Desm. 1880, p. 47, t. 18, f. 3 ; West & G-. S. 

 West, Alga-fl. Yorks. 1900, p. 41 ; Nordst. Index Desinid. 1890, p. 173. 



Palmoglcea mirifica Rabenh. Flor. Europ. Alg. Ill, 1808, p. 117. 



Cells broadly elliptical or oblong-elliptical, 1^-2^ 

 times longer than their diameter, straight or rarely 

 slightly curved ; chloroplast in the form of a very 

 narrow axile plate which is often curved. 



