64 BRITISH DESMIDIACE^. 



series round the angles. Vertical view triangular, sides 

 strongly concave, angles acutely rounded. 



Zygospore, according to Wittrock, spherical, provided 

 with a number of stout processes, trifid or bifid for about 

 half their length, and each part bifid again at its apex.* 



Length, without spines, 42'5-44 pi ; breadth 38-47 [JL ; 

 breadth of isthmus 1 1 p ; length of spines about 2 y. ; 

 diam. zygosp., without spines, 56-57 [i ; with spines, 

 88 pt. 



ENGLAND. Cumberland ! Westmoreland ! Lanca- 

 shire ! W. and N. Yorks ! Essex ! Oxford ! Plankton 

 of Bracebridge Pool, Warwicks ! Surrey ! Kent ! 

 Hants ! Devon ! Cornwall ! 



WALES.- -Fairly general ! 



SCOTLAND. General, but scarce ; zygospores from 

 Cammie, Kincardine and GlenCoe, Argyle (Roy <& Biss.). 

 Newton Stewart, Wigtown ! Near Lochmaddy, N. Uist, 

 and N. of Stornoway, Lewis, Outer Hebrides. Plankton 

 of the Orkneys and Shetlands. 



IRELAND.- -Donegal ! Mayo and Clare Island ! Gal- 

 way ! Kerry! Dublin and Wicklow (Arch.). Down (at 

 2000 feet on Slieve Donard) ! Londonderry ! 



Geogr. Distribution. Germany. Galicia and Austria. 

 Hungary. Norway. Sweden. Bornholm. Portugal. 

 Finland. N. Russia. Faeroes. Iceland. Spitzbergen. 

 Greenland. Siberia. Central Africa (var.). 



It is in the case of a species such as St. pilosum that the loss 

 of Professor West's critical remarks is to be most deplored. Unfor- 

 tunately information concerning this species is entirely wanting 

 in all his publications. The fact that certain correspondence 

 passed between him and the Austrian algologist, Dr. Lutkemuller, 

 shows that he was in some doubt about the species. Dr. Lutke- 

 muller had examined all the exsiccate of supposed St. pilosum 

 that he possibly could, and it is clear from a perusal of the cor- 



* The writer is of the opinion that it is very doubtful whether the Desmid 

 figured by Wittr. (' Skand. Desm.' 1869, 1. 1, f. 8), really was St. pilosum, since it 

 agrees more nearly with St. hirsutum in the form of its semicells. In that case 

 the figure of the zygospore given by Wittrock and reproduced on PL CXXXVIII, 

 f. 2, may not be correct for St. pilosum. This zygospore is, indeed, very similar 

 to Lutkemuller 's figure of the zygospore of St. hirsutum (cf. PL CXXXVIII, 

 f. 6). 



