COSMAKIUM. 107 



(Wills), Gloucester (Rcdfs). Surrey (zygospores from 

 Thursley Common) ! Sussex (Ralfs). Kent! Hants! 

 Wilts ! " Devon ! Cornwall ! 



WALES. Common ! At 2700 ft. on Grlycler Fawr 

 and at 2200 ft. on Grlycler Fach, Carnarvonshire ! 



SCOTLAND.- -General ! (Roy fy JBissett). Common in 

 the Outer Hebrides ! Orkneys ! Shetlands ! 



IRELAND. General, but not very abundant ! 



e/ 



Geogr. Distribution.- -France. Germany. Austria 

 and Galicia. Hungary. Italy. Norway. Sweden. 

 Denmark. Finland. Poland. N. and S.Russia. Faeroes. 

 Greenland. Singapore. Australia. W. Africa. United 

 States. W. Indies. 



C. Cucurbita occurs most abundantly in Sphagnum- 

 bogs, and is frequently associated with EuastriDii insigne, 

 XanMdium armatum, Arthrodesmus Incus, Gymnozyga monili- 

 f or mis, and other bog-loving species. It is distinguished by 

 its shortly cylindrical cells, with the evident median con- 

 striction, by the strongly punctate cell-wall, and by the single 

 central pyrenoid in each axile chloroplast. The poles of the 

 cell exhibit much variation in form; sometimes they are 

 hemispherical, but more often considerably flattened. The 

 species varies greatly in size, the smallest known form (var. 

 minimum W. & Gr. S. West, f Welw. Afric. Freshw. Alo-/ 



' O 



1897, p. 176) having a length of only 12'5^u and a breadth of 

 7'5 /a. The average size of the British examples is about 40 /u 

 in length and 20 JJL in breadth. 



We are convinced that the Desmicl which has frequently 

 been recorded as " C. Palangula Breb. var. Debdryi Rabenh/' 

 is only one form of C. Cucurbit a, as it agrees with the latter 

 species in all its essential features. 



The adult zygospores of C. Cucurbita are globose and 

 verrucose. We had at one time described them as smooth 

 (vide West, in ' Xaturalist/ Aug. 1891, p. 246; W. & G. S. 

 West, ' Alg. S. England/ 1897, p. 492, t, 6, f. 26), but have 

 since found that these zygospores were immature. 



Forma major. (PL LXXIV, fig. 2.) 



C. Cucurlita forma major "VYest^ Alg. "W. Ireland, 1892, p. 162. 



Length 60 ^ ; breadth 30 ^ ; breadth of isthmus 25 p.. 

 IRELAND. Ballynahinch, Grahvav ! 



7 . 



