i8o ASEXUAL REPRODUCTION OF ULOTHRIX 



(a) Reproduction of Ulothrix. — The contents of any of the 

 green cells may divide into two or more cells which escape as 

 zoospores through an opening formed in the cell wall (Fig. ill, 

 A). The cells in which the zoospores are formed are called 

 sporangia. The zoospores resemble the motile plants noted 

 above, but after a short motile period they return to the station- 

 ary condition and grow into new plants (Fig. iii, C). In this 



Fig. 1 10. 



Fig. III. 



Fig. 1 10. Lower portion of Ulothrix, the basal cells are somewhat modi- 

 fied and the lowest one acts as an anchoring organ. Each of the upper cells 

 contains a girdle-like chloroplast. 



Fig. III. Asexual reproduction of Ulothrix: A, a few cells of a fila- 

 ment in the upper cells of which the formation and escape of the large zoo- 

 spores are shown, while in the lowest cells a large number of small zoospores 

 appear. B, a large zoospore. C, a young plant formed by B. D, a small 

 zoospore. E, a young plant formed from D. — After West. 



way, the number of plants is rapidly multiplied and it should be 

 stated that the asexual method of reproduction may be looked 

 upon as a means of bringing aboul a rapid increase in the number 



