1 o I BK1TISII DKSAIIDIACK.K. 



This occurred with the typical form, V>ut was more 

 abundant. 



3<>. Closterium Siliqua West & (I. S. West, 

 (PI. XIX, figs. 0-8.) 



Closterium Hil'ujtm. West & G. S. West, Alt?. 8. England, IS'.iT, p. -1-so, t, li. 

 f. 1, 2. 



Cells moderately largo, aJ)out 10 times longer than 

 their diameter, slightly curved, outer margin 30 35 

 of arc, inner margin very slightly concave, margins 

 almost parallel in the middle of the cell for about one- 

 third its length, gradually attenuated towards the 

 apices, which are narrow, subtruncate, and slightly 

 recurved ; cell- wall smooth and colourless ; chloroplasts 

 with about six ridges, and a single, somewhat irregular 

 series of 7 or 8 pyrenoids ; terminal vacuoles with only 

 one large, oblong, moving granule. 



Zygospore unknown. 



Length 217-250 /x,; breadth 21-24 /x; breadth of 

 apices 4/z. 



ENGLAND. Esher West-end Common, Surrey! 



CL Siliqua is distinguished from Cl. Pritchardianum Arch. 

 by its much smaller size,, its much more tapering and narrower 

 extremities, as well as by its smooth and colourless membrane. 

 From CL littorale Gay ; it differs in being a little longer, in 

 the absence of the slight ventral inflation, and in the blunter 

 and slightly recurved apices. It may also he compared with 

 Cl. subangulatum Grutw. from which it differs in the sub- 

 parallel median portion of the cells, in the absence of the 

 ventral inflation, in the more convex outer margin, as well as 

 in the recurved apices. From all the above, the living 

 examples art: distinguished by the terminal vacuoles possessing 

 but one oblong moving granule. 



31. Closterium peracerosum Gray. 

 (PI. XIX, figs. 9-11.) 



C'/'/.S/,'/-MM<I peracerosum G;iy, MUIIO^T. luc. C'mij. INN.)., p. 75, t. 2, f. 18 ; 



!>< Toni, Syll. Altf. 1889, p. 825; West & G. S. West, Alga-fl. Yoi-ks. 



1!)00, p. 53 ; Alg-. N. Ireland, 1902, p. 23. 

 Arilu;i<liii i>i'rc<'i'<>!iii Kimtze, Eovis. g'en. plant. 1891, p. 88-4. 



