.MESOT/KN1UM. 51 



Zygospore unknown. 

 Length 25-42-5 /*; breadth 15-20/u. 

 ENGLAND. - -Stickle Tarn, Westmoreland! Ogdcn 

 (Hoim-h and Ino-leton, W. Yorks ! Leicester (Ltoi/). 



o O 7 \ 



WALKS. -Llyn Idwal, Carnarvonshire! 

 SCOTLAND. Harris, Outer Hebrides ! Groat Fell, 

 Arran ! 



IRELAND. Dublin and Wicklow (Archer). 



Archer observed the formation of asexual spore-like bodies 

 iu this plant ; they were of a brown colour and of an average 

 diameter of about 25 p. He says : " I have observed the cell- 

 contents bounded by the primordial utricle escape from the 

 parent-cell without conjugation, through a lateral or terminal 

 or intermediately disposed opening, effected by the raising up 

 and often the separation of a lid or valve-like portion of the 

 parent-cell membrane. During this operation the contents are 

 often much constricted, by reason of the narrow orifice through 

 which the mass makes an exit. After emergence it becomes 

 rounded, and the contents of this resting-spore-like body, 

 which do not conjugate or combine with any other, become of 

 a reddish-brown hue, with a dark corpuscle in the centre. The 

 rmptv parent-cell membrane lies hard by, the lid-like structure 

 sometimes apparently still adherent by one point sometimes 

 wholly detached, and lying about in various positions, or lost 

 altogether." 



The elliptical outline of the cells is sufficient to distinguish 

 this species from M. iiMcrococcum and M. chlamydosporum. 



3. Mesotaenium macrococcum (Kiitz.) Roy & Bissett. 



(PI. Ill, figs. 34-36.) 



Palmoijlcea macrococca Kiitz. Phyc. germ. 1S45, p. 153; Tab. Phycolog. 



1S47, I, t. 24, f. 2; Spec. Alg. 1849, p. 22S ; liabenh. Flor. Europ. A1-. 



Ill, 1868, p. 115 ; Nordst. Index Desmid. 1896, p. 162 ; Arch. Palmoglcea 



and descrip. Mesot. 1864, p. 12-14. 

 Mesotaenium Braunii De Bary, Conj. 1858, p. 74, t. 7 A, f. 1-8; Kirchn. 



Aly. Sclilus. 1878, p. 134; Wolle, Desm. U.S. 1884, p. 31, t. 3, f. 5-9; 



Turn. Freshw. Alg-. E. India, 1893, p. 15. 

 Mesotaenium mM-rococcum (Kiitz.) Roy & Biss. Scott. Desm. 1894, p. 61 



(sep.) ; West & G-. S. West, Alga-fl. Yorks. 1900, p. 41. 



Cells cylindrical, 2-2^- times longer than their dia- 

 meter, apices truncately rounded ; chloroplast a strong 

 axile plate, often with a toothed margin. 



Zygospore somewhat quadrate with rounded angles. 



