84 BRITISH UESMIDIE/E. 



as long as broad ; each segment is inflated at its base, the sides of which are 

 entire, and tapers upwards into a slender neck without lateral tubercles ; ter- 

 minal lobe dilated, its notch linear and frequently obscured by the inflated 

 prominences. The end \-iew is cruciform. 



The transverse view difi'ers from that of every other species, for in them the 

 outline is elliptical, or broadest at the centre, but in this plant the sides are 

 straight, with a little constriction at the centre and a slight swelling or lobe 

 near each extremity ; indeed without the end lobes the form would be nearly 

 quadrangular. The empty frond is punctate. 



Mr. Sidebotham has gathered a conjugated specimen of this species near 

 Ambleside. 



The inflated base and slender neck, conjoined with its dilated end, are suffi- 

 ciently characteristic. 



To avoid a needless multiplication of synonyms, I have here adopted the 

 name under which Mr. Hassall has figured it in his work on the British Fresh- 

 water Algse, although in a paper read before the Botanical Society of Edin- 

 burgh I had pre\'iously called it Euastriim gi'cicile, and had distributed speci- 

 mens under that name, from some of which indeed Mr. Hassall obtained his 

 knowledge of the species, a circumstance that he has omitted to notice. 



Length of frond -^\^ of an inch ; breadth at base ^\-q ; breadth at end -^^ ; 

 breadth of neck -ytt2- 



Tab. XIII. fig. 6. a. frond with endochrome ; b. empty frond ; c. side Aiew ; 

 d. transverse view ; e. end \'iew. 



9. E. Didelta (Turp.) ; segments with inflated base, intermediate 

 tubercles, and notched and scarcely dilated end ; transverse view, 

 four shallow lobes on each side and one at each end. 



Heterocarpella Bidelta, Turp. Mem. p. 295 (1828). 

 Costnarhan Didelta, Menegh. Synop. Desmid. in Linncea 1840, p. 219. 

 Euastrum Didelta, Ralfs, Ann. of Nat. Hist. v. 14. p. 190 (in part), t. 7. f. 2. 

 a, h. (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 12/. t. 11. 



Common. Carnarvon, Dolgelley, Penzance, &c., J. R. Near Tuubridge 

 Wells ; near Battle, Henfield, Midliurst, Sussex ; and Hampshire, Mr. Jenner. 

 Westmoreland, Mr. Sidebotham. Aberdeen, Dr. Dickie and Mr. P. Grant. 



Falaise, Brebisson. New York, Bailey. 



Frond comparatively large, about thrice as long as broad ; segments pyra- 

 midal, inflated at the base, and tapering upwards hito the intermediate tuber- 

 cles ; the neck is broad, and the end slightly dilated, with a terminal linear 

 notch. The end view is bilobed, and the transverse one elliptic with four 

 slight lobes on each side and one at each end. The empty frond is punctate. 



Euastrum Didelta difi'ers from the preceding species in the slight dilatation 

 of the end lobes, and in the end view the two lobes are entire. 

 ; The sporangia, which I have twice found at Dolgelley, are orbicular, and 

 have subulate spines. 



Length of frond -^^ of an inch ; breadth at base -jiy ; breadth at end j\-^ ; 

 breadth at constriction ToVn '> thickness in side view -x^-r. 



