ANNUAL DISTRIBUTION OF THE ORGANISMS. 37 



Britain, should receive a little attention although it has been 

 thoroughly discussed, in its general aspects, by other authors. 

 This phenomenon is especially marked in Lake Winnebago in 

 some summers. It is due, of course, to the enormous growth 

 of the plants of the plankton, that growth being particularly 

 fostered by the hot weather of midsummer. The plants espe- 

 cially concerned in forming the bloom are Clathrocystis, Ana- 

 baena, Aplianizoinenon, Oscillaria, Lingbya, and Gloiotrichia. 

 The times of occurrence of these plants have already been no- 

 ticed in the discussion of the individual constituents of the 

 plankton. At the middle of August, in some summers, on a 

 still day, the surface of Lake Winnebago is apparently a solid, 

 opaque green. Some of this material decomposes, and as the 

 currents slowly move along the surface material, it shows a 

 wavy streaked appearance like the surface of polished mala- 

 chite. Its intrinsic beauty, however, does not attract the aver- 

 age person, for he looks upon it as "scum," and he thinks of it 

 simply as an evidence of filth. This material is thrown upon 

 the shores by the waves until the rocks alongshore are completely 

 covered with it, and it may in its decay become very offensive. 

 Following the maximum period of the "bloom" Cladophora ap- 

 pears and covers the littoral rocks with a thick mat of green. 

 This great growth of "bloom" naturally attracts the attention of 

 the non-scientific observer, and many absurd explanations of its 

 presence are given. The most common one in Oshkosh is that it 

 is a mass of seeds coming from the marshy shores of the Fox 

 and Wolf above Oshkosh. Doubtless the Anabaena and Gloio- 

 trichia have given rise to the supposition that the bloom is a 

 mass of seeds. The decomposition of Gloiotrichia produces a 

 blood red coloring matter which is sometimes very noticeable on 

 the shores of Lake Winnebago, and has led people to question 

 as to whether the lake is not affected by one of the plagues of 

 Egypt. 



When the water is still the plants of the bloom are in greatest 

 abundance, close to the surface, and are distributed very uni- 

 formly over the lake. Frequently, in the latter part of July 



