20 BRITISH CHAEOPHYTA. 



{tp.) of limited growth, consisting of a variable 

 number, usually about four, of more or less elongated 

 cells, arranged longitudinally. The pro-embryonic 

 whorl consists of several cylindrical incurved processes 

 of varied length but of limited growth, growing out- 

 ward and upward, each process composed of a single 

 row of a few cells. The earlier stages in the develop- 

 ment of the pro-embryonic whorl will be seen in PI. 

 Ill, figs. 10-12. 



It is as a lateral bud in the axil of this whorl that 



Fio. 2. — Transverse sections of root-node of pro-embryo of Ohara 

 canescens, showing successive stages of division (after De Bary and 

 Kamiensisi) ( y c. 100). i, ii, iii. Early stages, iv. Advanced 

 stage showing outgrowths (a h c) of rhizoids. This section is 

 somewhat oblique, a a arising below and h above the section 

 plane ; c c are older rhizoids. 



the complete (sexual) chara-plant originates (PL III, 

 f. 6 sp). This course of development can hardly be 

 regarded as representing an alternation of generations. 

 Vines refers to it as " heteroblastic, an embryonic 

 form intervening between the oospore and the adult," 

 and regards the pro-embryo as analogous to the pro- 

 tonema of a moss. 



The successive divisions of the pro-embryonic whorl- 

 node and the origin of the sexual plant are shown in 



