356 



Annals New York Academy of Sciences 



classification included 4 groups, namely (1) richly branched thalli; (2) long, 

 flexible cylinders, (3) spherical cushions, and (4) simplified platelike forms. 

 The second of these groups should probably be modified to include forms with 

 laciniate, reticular or lacunate bodies which float downstream from a point of 

 attachment; it should also be pointed out that certain algae with short un- 

 branched filaments, although they indeed qualify as cylinders, nevertheless 

 have a somewhat unique superficial form since, as in Vaucheria, they frequently 

 constitute a virtual turf but do not become interwoven to form massive skeins 

 as in the first group. If body form is a major criterion for these groups, at 



Cladophora glomerata 



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Figure 1. Cladophora glomerata. The illustration at bottom represents several algal 

 thalli X'2 attached to a portion of rock (stippled). The upjier drawings represent increasing 

 magnifications of small portions of the thallus. 



least one other category should probably be added for forms with a rigid, 

 cylindrical, but pseudoparenchymatous body like Lemanea. 



The first 2 groups as outlined by Cedergren can be summarized by the 

 qualification that they live in the current and permit water to run among their 

 filaments or at least on more than one side of the thallus. Hence they e.xpose 

 a large surface area directly to the surrounding water. A common example 

 of this type is Cladophora glomerata (L.) Kiitz. (figure 1). These groups can 

 be further subdivided into gelatinous and nongelatinous types. The gelat- 

 inous types in general have relatively small filament or trichome diameter. 



The last 2 groups of Cedergren can be qualified by virtue of their position 

 mostly below the current — in other words they become a part of the stream 

 bottom. The current docs not flow among their filaments but only in their 



