1 84 ASEXUAL REPRODUCTION OF VAUCHERIA 



branching and anchored to the ground by colorless outgrowths 

 (Fig. 113, A). The protoplasm forms a thick lining layer on 

 the inner wall of the filament and embedded in it are numerous 

 minute chloroplasts, nuclei and oil drops. A watery cell sap 

 fills the center of the tube. Partitions only appear when repro- 

 ductive bodies are formed or to close a wound in case of injury 

 to the filaments. Asexual reproduction is effected by very large 

 zoospores which are developed in the enlarged extremities of the 

 filaments (Fig. 113, B). These tips are cut off by a transverse 

 wall and a single zoospore escapes through an opening in the 

 tip of the sporangium thus formed. The entire surface of the 

 zoospore is clothed with cilia arranged in pairs, each pair being 

 associated with a nucleus so that the zoospore resembles the mo- 

 tile colonies previously noted (Fig. 113, C). After a very short 



Fig. 113. Structure and asexual reproduction of Vaucheria: A, portion 

 of a plant showing the branching tubular filament and colorless root-like 

 outgrowth, r. B, end of a filament enlarging to form a zoospore. C, zoospore. 

 D, germination of a zoospore. 



motile period, the zoospore comes to rest and grows into the 

 characteristic tubular plant (Fig. 113, D). When the plants are 

 exposed to too dry conditions, the tips of the filaments often 

 enlarge and finally become detached as motionless spores that 

 germinate when conditions are again favorable. 



