DEVELOPMENT OF PLANTS 



191 



of this nature, one or more of the basal cells becoming slightly 

 changed in form and contents and so adapted in anchoring the 

 plant. The other cells of the plant are practically alike, each con- 

 taining a single nucleus and chloroplast and therefore capable of 

 manufacturing food and forming the reproductive bodies which 

 are of the same simple type as noted in Sphaerella. 



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

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



Fig. iio. Fig. hi. 



Fig. ho. 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. 



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

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



