COSMAEIUM. 6 



ellau, Ross (L'oi/ $ Sissett). Orkneys! Shetlands ! 

 Lewis, Harris, N. and S. Uist, Outer Hebrides ! 

 Common in the plankton ! 



IRELAND. Common ! Plankton of the lakes of 

 Mayo, Grahvay, and Kerry ! 



Geogr. Distribution.- -France. Belgium. Germany. 

 Austria and Galicia. Ronmania. Bosnia. Hungary. 

 Italy. Portugal. Norway. Sweden. Denmark. Born- 

 holm. Finland. Poland. 1ST. and S. Russia. Faeroes. 

 Iceland. Xova Zembla. Spitsbergen. Greenland. 

 Siberia. Mongolia. China. Japan. Afghanistan 

 (var.). Ceylon. Burma (var.). New Zealand. Azores. 

 United States. Brazil. Argentina. Pataeronia. 



o o 



C. Botrytis is the most generally distributed species of the 

 germs in the British Islands, and possibly in the whole of 

 Europe. It is found in all kinds of situations from stagnant 

 hogs to well-aerated, dripping rocks, hut occurs most abun- 

 dantly at the margins of pools and lakes. It is not uncommon 

 in the freshwater plankton, and in small pools it is frequently 

 found with zygospores. The granulation of the cell-wall is 

 of a uniform character, and the granules as a rule have no 

 definite disposition. The form of the semicell is somewhat 

 variable, but it is always distinctly pyramidate, with convex 

 sides, and an apex which is more or less truncate. 



Within the arctic circle the species is often rather diminutive, 

 and Boldt records specimens from Greenland with a length 

 of only 49'2/i and a breadth of 43'2ju. 



Being such a cosmopolitan species, C. Botrytis exhibits a 

 considerable amount of variability, and in consequence of 

 this it has been overloaded with named varieties. We have 

 attempted to clearly draw up the characters of about seven of 

 these varieties, which have been discovered in various parts 

 of the British Islands. 



The development of the zygospore is better known in C. 

 Botrytis than in any other species of the tribe Cosmarieae. It 

 was worked out by De Bary in 1858 (Consult Vol. I, p. 11, 

 and this volume, PL XCVI, figs. 7-15). 



Wille (' Ferskv. Alg. Nov. SernljV 1879, p. 35) has described 

 a "forma obliqua" in which one side of the vertical view is 

 flat and the other almost semicircular; length 63 /x; breadth 

 46 ILL. Both semicells were apparently deformed, their outline 

 in front view being somewhat irregular. 



