BRITISH DESMIDIE.K. 83 



Frond about three times as long as broad ; segments pyramidal, thrce-lobed, 

 and ha\-ing on each side a tubercle, which replaces the middle lobes ; the end 

 lobe is dilated and its notch linear ; the basal lobes are emarginate and sud- 

 denly contracted beneath the tubercles, which are smaller than in the last 

 species, and have their upper margins nearly horizontal, by which it may be 

 distinguished from it. The transverse view also has four lobes on each side 

 instead of three. The empty frond is punctate. 



Euastnim affine differs from E. pinnatum by its smaller size, by being 

 sinuated, not pinnatifid, and by the lobes being less prominent in the trans- 

 verse view. In E. pinnatum we find the segments distinctly five-lobed, but 

 in this and some other species the middle lobes are replaced by tubercles more 

 or less developed. 



Length of frond -^\q of an inch ; breadth at basal lobe -j^-g- ; breadth at 

 middle lobes -g-|-9 ; breadth of neck ^^^^ ; breadth at end -^\j. 



Tab. XIII. fig. 3. a. mature frond with endochrome ; h. empty frond ; 



c. side view ; d. end view ; e. transverse view. 



7. E. ampullaceum ; segments short, with inflated base, small in- 

 termediate tubercles, and a dilated, notched, terminal lobe. 



Euastrum , Hass. Brit. Freshwater Algce, t. 100. f. 11. 



Dolgelley, /. R. Ambleside, Westmoreland, Mr. Sidebotham. Near Tun- 

 bridge AVells and near Storrington, Sussex ; and Hampshire, Mr. Jenner. 



Frond smooth, twice as long as broad, rather smaller than Eyastrvm affine. 

 The base is much-inflated, and is separated from the small intermediate tuber- 

 cles by a slight constriction. The terminal lobe is dilated, its outline usually 

 more convex than that of the other species, and it tapers more gradually into 

 the very short neck, hence it appears more cuneate or fan-shaped ; its notch is 

 linear. 



Euastrum ampullaceum may be best recognized by its short segments, in 

 which and its broad inflated base it differs from E. affine, whilst the distinctly 

 dilated terminal lobe separates it from E. Didelta. 



The empty frond is punctate, and the inflated protuberances on its front 

 surface are indistinct. 



Length of frond g-fz of an inch ; breadth of base -^-j ; breadth at end y-|-g- ; 

 breadth of neck ytt^- 



Tab. XIII. fig. 4. a. frond with endochrome ; b. empty frond ; e. side view ; 



d. transverse \'iew. 



8. E. insigne (Hass.) ; segments inflated at the base and tapering up- 

 wards into a slender neck ; end dilated, emarginate ; transverse 

 view with two distant lobes on each side and one at each end. 



Euastrum insigne, Hass. Brit. Alg. t. 91. f. 2. (1845). 



Dolgelley, J. R. Midhurst, and Fittleworth Common near Petworth ; and 

 New Forest, Hants, 3Ir. Jenner. Ambleside, 3Ir. Sidebotham. Moss Hagg, 

 Banffshire (altitude 3000 feet), Mr. P. Grant. 



Frond rather smaller than that of Euastnua Didelta, about three times 



G 



