THE ALGM 159 



genus Bulbochcete, which chiefly differs from (Edogonium 

 in having branched instead of simple filaments. Its 

 significance is not perfectly understood ; possibly by 

 dividing the period of locomotion into two stages (first, 

 the swarming androspore, and secondly, the swarming 

 spermatozoid) the chance of the male cell reaching an 

 oogoniumat the right time may be increased. 



TYPE X. ULOTHRIX ZONATA 



1. STRUCTURE 



We will next consider another fresh-water Alga, not at 

 all unlike (Edogonium in general habit, but representing 

 a very different and much lower type of reproduction. 

 UlotJirix zonata is an extremely common Alga, of the 

 filamentous or confervoid kind, 1 growing by preference 

 in running streams, or in water which is constantly 

 renewed, as in brooks, open watercourses, or in open-air 

 tanks with a constant supply. 



The thread which constitutes the Alga is very 

 slender, not usually exceeding about *025 millimetre 

 (one-thousandth of an inch) in diameter. The filament 

 consists of a single row of cells, often very numerous, 

 amounting to a thousand or more in a single thread. 

 The threads are usually attached at one end to the stones 

 or other things in the water, but they can live equally 

 well detached, floating in tangled masses on the surface. 



1 Simple filamentous Algae are often spoken of as confervoid, because all 

 such forms were in the days of Linneus included in the old genus Conferva, 

 which since that time has been subdivided again and again, as the 

 important distinctions among the species originally referred to it came 

 to be better understood. 



