BRITISH DESxMIDIE^E. 75 



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



broadest. 



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

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

 dentate. 



Cosmarium truncntum, Corda, Aim. de Carlsb. 1835, p. 121. f. 23. 

 Euastrum Rota, Ehr. Infus. t. 12. f. 1. g, h. (1838). 

 Micrasferias Rota (yomig), Menegli. St/nop. Desmid. p. 215 (1840). 

 Euastrum semiradiutum, Brcb. inMenegh. Synop. Desmid. (1840). Kiitzing, 



Phycoloyia Germ. p. 134. 

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

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



(1844) ; Trans, of Bot. Soe. o/Edin. v. 2. t. 10. 

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



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

 J. R. Aberdeen, Dr. Dickie and Mr. P. Grant. Near Bristol, 3Ir. Broome. 

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



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



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

 rating sinuses shallow, especially those between the lateral and mtermediate 

 lobes. The corners of the terminal lobe, which is broadly cuueate 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 distinct, 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 Brebisson and 

 Professor Kiitzing, 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 2^ of an inch ; breadth -g-L . 



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, Ami. 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. vn lit. (1846). 



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



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

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



