Desmidiacece 



167 



size in the middle of each face of the semicell, so that the vertical 

 view, which is elliptical in some species, may in others be furnished 

 on each side with a more or less prominent swelling. 



In the majority of species there is one central chloroplast in 

 each semicell, possessing four somewhat curved longitudinal plates 

 and either one or two large pyrenoids. In a few species there are 



Fig. 62. A, Cosmarium reniformc (Ralfs) Arch, (a form), from Wicken Fen, Cambs. 

 (x473). B, C. granatum Br6b., from Chippenham Fen, Cambs. ( x 473). C 

 and D, C. yranatum var. subgranatum Nordst., from Hornsey Mere, E. Yorks. 

 ( x 473). E G, C. Meneghinii Breb. ; E and F, from Hornsey Mere, E. Yorks.; 

 G, zygospore of a form from Bowness, Westmoreland ( x 473). H, C. prce- 

 morsum Breb., from Carrantuohill, Kerry, Ireland (x473). I and J, C. 

 bioculatum Bre*b.; I, from Boswell Pits, Cambs.; J, zygospore from Puttenham 

 Common, Surrey (x473). K and L, forms of C. Regnesii Beinsch; L shows 

 one stage of cell-division ( x 1170). M, C. isthmium West, from Harris, Outer 

 Hebrides ( x 473). N, C. pseudoconnatum Nordst., from Capel Curig, N. Wales 

 ( x 473). /, front view ; s, side or lateral view ; v, vertical view. 



several (from four to eight) parietal chloroplasts in each semicell, 

 each containing one or more pyrenoids. 



Some investigators of these plants have attempted to establish 

 Nageli's genus Dysphinctium ( Calocylindrus Kirchn.) in order 

 to include certain species which are best left in the old genus 



