BRITISH DESMIDIE^. 7^ 



*** Fronds orbicular ; segments obscurely five-lobed, the end one 



broadest. 



1). M. truncata (Corda) ; frond orbicular ; segments with five shal- 

 low lobes, the end one very broad, truncated, lateral ones inciso- 

 dentate. 



CosmariuM tnincatum, Corda, Aim. de Carhb. 1835, p. 121. f. 23. 

 Euastrum Rota, Ehr. Infus. t. 12. f. \. g, h. (1838). 

 Micrasterias Rota (yoimg), Menegh. Synop. Besmid. p. 215 (1840). 

 Euastrum semiradiatum, Breb. in Menegh, Sj/noj}. Desmid. (1840). Kiitzing, 



Phycoloyia Germ. p. 134. 

 Euastrum (No. 4), Bailey, Amer. Bacil. f. 24. (1841). 

 Micrasterias rotata, Ralfs, Atinals of Nat. Hist. v. 14. t. 6. f. 1. b. (inferior) 



(1844) ; Trans, of Bot. Soc. of Edin. v. 2. t. 10. 

 Micrasterias truncata, Breb. in lit. (1846). 



Common. Sussex and Hampshire, Mr. Jenner. Dolgelley, Penzance, &c., 

 /. R. Aberdeen, Dr. Dickie and Mr. P. Grant. Near Bristol, Mr. Broome. 

 Ambleside, "Westmoreland, Mr. Sidebotham. Kerry, Mr. Andrews. 



Germany, Corda, Kutzing. Falaise, Brebisson. United States, Bailey. 



The frond is minute and circular, the segments are five-lobed, and the sepa- 

 rating smuses shallow, especially those between the lateral and intermediate 

 lobes. The comers of the terminal lobe, which is broadly cuneate and truncate, 

 are bidentate, and the lateral lobes are inciso-dentate. 



Mr. Jenner and myself have hitherto differed respecting this plant. He 

 has considered it distmct, whilst I have been disposed to regard it as the 

 young state of M. rotata, and it was figured as such in the plate (already 

 engraved) of that species ; but I have learnt since from M. de BrcTjisson and 

 Professor Kutzing, that they entertained no doubt of the distinctness of this 

 species and had so described it, and I have myself met with specimens con- 

 taining in abundance starch vesicles ; I therefore hasten to admit its claims to 

 the rank of a distinct species. 



Length of frond -^\-^ of an inch ; breadth -^. 



Tab. VIII. fig. 4. and Tab. X. fig. 5. a. frond with endochrome ; b. empty 

 frond ; c. end view ; d. side view. 



10. M.crenata (Breb.); frond orbicular; segments with five shallow 

 lobes, the end one very broad and convex at the margin, lateral 

 ones nearly entire. 



Micrasterias rotata, Ralfs, A7in. of Nat. Hist. v. 14. t. 6. f. 1. b. (superior) 



(1844) ; Trans, of Bot. Soc. of Edin. v. 2. t. 10. 

 Micrasterias crenata, Breb. in lit. (1846). 



Dolgelley, J. R. Sussex, Mr. Jenner. 



The frond is minute, of the same size as that of 31. truncata, and cir- 

 cular. The segments are five-lobed, the terminal one broad, cmieate, entire 

 and rounded at the margin. The lateral lobes are sometimes entire, but more 

 usually crenate, occasionally having a few inconspicuous teeth. 



M. crenata differs from M, truncata in the convex margin of its end lobes 



