98 BRITISH DESM1DIACE.1-:. 



WALES. Capel Curig, Llyii Cwlyd, Bethesda, Car- 

 narvonshire ! Ffestiniog, Merioneth ! 



SCOTLAND. Aberdeen, Kincardine, Perth ! (Emj $ 

 Bissett). Skye in Inverness ! Forfar ! Kirkcudbright ! 

 Harris, Outer Hebrides ! Shetlands ! 



IRELAND. Dublin and Wicklow (Arclicr). Slieve- 

 commedagh, Down ! 



Geocjr. Distribution. France. Germany. Austria. 

 Italy. Norway. Sweden. Greenland. Spitzbergen. 

 Xova Zembla. Franz-Joseph Land. India. Biirmah. 

 Siam. West Africa. Madagascar. West Indies. 

 United States. 



Tliis Desmid varies much in size within certain limits. 

 There is no definite line of demarcation between any of these 

 forms, every intermediate size being met with, but for con- 

 venience they may be classified as follows : 



(I) Forma minuta West. 



Penium curium forma minuta West, Alg. Eng. Lake Distr. 1892, p. 721. 

 Length 22-25 /t; breadth 10-5-11-5 p. 



(2) Forma minor Wille. (PI. X, fig. 23.) 



Penium curium forma minor Wille, Ferskv. Alg. Nov. Semlj. 1879, p. 5(5, 



t. 14, f . 75. 

 DyspJiinctium curium var. exiguum Hansg. in Oesterr. bot. Zeitschr. 1887, 



xxxvii, p. 57 ; Prodr. Algenfl. Bohm. 1888, p. 184. 



Length 28-32 fi- breadth 12-17 ,u. 



(3) Forma intermedia Wille. 



P. curium forma intermedia Wille, 1. c. f. 74. 



Length 34-38 ,i breadth 16-19 ,,. 



(4) Forma major Wille. (PI. X, figs. 24, 25.) 



P. curium forma major Wille, 1. c. f. 73. 

 Length 42-60 ^- breadth 20-32-5 ,,. 



Penium cm-turn is a well-marked species by reason of its 

 short cells with attenuated semicells. It is principally an 

 upland Desmid, occurring amongst Sphagnum and amongst 

 wet mosses on rocks. It sometimes occurs in pure masses ,in 

 temporary pools of rain-water on road-sides, in cart-ruts, etc. 



