BRITISH desmidie>t:. 99 



Frond large, oval, tviice as long as broad, deeply constricted at the middle ; 

 the apposition of the segments for their entire breadth ren<lers tlie notch on 

 each side Imcar ; the pearly granules are large and confined to the margin, 

 where they form three to six series, the largest and central row producing 

 a dentate appearance ; the rest of the frond is merely punctate. 



The endochrome of each segment is often longitudinally divided by a pale 

 line. The transverse view is elhptic. 



Cosmarium ovale is one of the largest species in the genus ; its oval form 

 and its disc devoid of granules sufficiently characterise it. 



Length of frond yig of an inch ; breadth of segment -^-^ ; breadth of con- 

 nectmg portion y-L. 



Tab. XV. fig. 9. a. front view of empty frond ; b. side view. 



13. C. Botrytis (Bory) ; frond granulate, deeply constricted ; seg- 

 mentSj in the front view, truncato-triangular ; end view elliptic. 



Heterocai'peUa Botrytis, Bory, Diet. Class, t. 8 (1825). 



Cosmarium deltoides, Corda, Aim. de Carlsb. 1835. p. 120. f. 18. 



Euastrum Botrytis, Ehr. Infus. p. 163 (1838). Kiitz. Phy. Germ. p. 13G. 



Euasti'um angulosum, Ehr. Infus. t. 10. f. 8 (1838). 



Cosmarium Boti'ytis, Meneghini, Synop. Desm. in Linnaea 1840, p. 220. 



Ralfs, in Annals of Nat. Hist. v. 14. p. 393. t. 1 1. f. 5 ; Trans, of Bat. 



Soe. of Edinburgh, v. 2. p. 15. t. 16. Hassall, Brit. Alg. p. 363. 



Dolgelley and Penzance, /. R. Bristol, Mr. Thwaites. Bexhill, &c., 

 Sussex, Mr. J(??««e/*. Manchester; and Ambleside, Ji/-. *S'/</f'6oMffw^ Essex, 

 Mr. Hassall. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Banffshire, 

 Mr. P. Grant. 



Germany, Ehrenberg. Falaise, Brebisson. 



Frond compressed, more or less rough with pearly granules, which give a 

 denticulate appearance to the margin, deeply constricted at the middle, the 

 constriction forming a linear notch on each side. In the front view the seg- 

 ments are broadest at the base and gradually narrower towards the end, which 

 is trmicated ; hence their figure is somewhat angular. The transverse view is 

 elliptic. 



The pearly granules are sometimes very evident, sometimes obscure, but 

 they can always be detected at the margin by the higher powers of the mi- 

 croscope. 



Mr. Thwaites has gathered a single sporangium near Bristol ; it was orlji- 

 cular, its spines elongated and slightly divided at the apex. 



Cosmarium Botrytis may be known from C. margaritiferum by its trmicate 

 ends ; and from C. pyramidatum by its more triangular segments and denti- 

 culate margins. 



Length of frond from -j^ to -giy of an inch ; breadth at constriction o^Vo 

 to YxTB" 5 breadth of segment -g-ig- to j J-g ; diameter of sporangium -^^ ; 

 length of spines of sporangium ^ /^ ^ . 



Tab. XVI. fig. 1. a. mature frond; b. empty frond; c. transverse view; 

 d. sporangium with empty fronds attached. 



H 



