DEVELOPMENT OF PLANTS 



191 



of this nature, one or more of the basal cells hecomin.i,^ sli^^htly 

 changed in form and contents and so adapted in an( horin^ the 

 plant. The other cells of the plant are praclicalh- 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 an\- of the 

 green cells may divide into two or more cells which esca[)e as 



10. 



Fi(.. III. 

 10. Lower portion of Ulothrix, the basal cells are somewhat nuHli- 



Fig. 



Fig. 



fied and the lowest one acts as an anchoring organ. Each of the up|K>r crils 

 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 larRe zcxi- 

 spores are shown, while in the lowest cells a large number of small Z(x>s|K>rc» 

 appear. B, a large zoospore. C, a young plant formed by /i. P, a small 

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



zoospores through an opening formed in the cell wall (I'ig. m, 

 A). The cells in which the zotJspores are f<'r"i<'l .«r.- .allrd 



