MESOTvENIUM. 49 



B. Cells free-swimming. 



* Cell-sap coloured purple or violet. 



8. M. purpureum. 

 ** Cell-sap uncoloured. 



t Cells straight, 3-4 times longer than broad. 



9. M. Endlicherianum. 

 ft Cells curved, 6-8 times longer than broad. 



10. M. Kramstai. 



A. Cells in mucilaginous masses, principally on wet 



rocks. 



1. Mesotaenium De Greyi Turn. 

 (PL III, figs. 18, 19.) 



DC Greyi Turn. Notes Freshw. Alg. 1886, p. 34, t. 1, f. 1; 

 Cooke, Brit, Desm. 1886, p. 48, t. 18, f. 6; West, Alg. W. Ireland, 

 p. 131 ; Alg. Eng. Lake Distr. 1892, p. 721 ; West & G. S. West, Alg. S. 

 England, p. 478; Alga-fi. York*. 19U<>, p. 41; Alg. N. Ireland, I'.)ii2, 

 p. 19 ; Norclst. Index Desmid. 189(3, p. 136. 



Mesotxnium Braunii De Bary, var. Greyi (Turn.) Roy in Scott. Nat. x, 

 1890, p. 206. 



Cells large, 4-4^ times longer than their diameter, 

 cylindrical, straight or curved, apices broadly rounded. 



Zygospore unknown. 



Length 76-104 p ; breadth 20-28 p. 



ENGLAND. Bowness, Westmoreland ! Blubberhouses 

 (Turner), Ilkley, Simon Seat, and near Settle, W. Yorks! 

 Puttenham Common, Surrey ! Tintagel, Cornwall ! 



SCOTLAND. - - Brseriach, Inverness ; Tough, Glen 

 Berry, and " Colonel's Bed," Aberdeen ; Kyles of Bute, 

 Argyll (Roij $ Bissett). 



ICELAND.-- Castletown, Kerry! Lough Nacung, 

 Donegal ! 



Geoyr. Distribution . Australia. 



This is the largest species of the genus ;m<l the cells fivijiii'iitly 

 become filled with reserve materials, often in the form of 

 large oil globules. 



Forma major forum itur. (PL III, fig. 21.) 



Cells rather larger than in the typical form, and 

 about 4 times longer than their diameter. 



4 



