18 



BRITISH CHALIOPHYTA. 





divided, longitudinally in relation to the axis of the 

 oospore, into three cells, the centre cell of which 

 grows out as the primary root, while the two lateral 

 cells form accessory roots. Further division takes 

 place in the three cells, numerous accessory rhizoids 

 and sometimes accessory pro-embryos (PI. II, f. 8 p r ) 

 being produced. The primary root elongates con- 

 siderably and forms nodes (PL II, f. 8 rn.) at which 

 rhizoids are produced. Rhizoids also originate at the 

 first and sometimes at the second node of the pro- 



IV 



VI 



FIG. 1. Successive development of root-node of Chara aspera (after 

 Giesenhagen) ( x c. 35). i. Root-filament with curved septum a 

 forming, " double-foot " joint. ii. Dilation of " toe " of upper 

 "foot" b. iii. Toe-portion cut off by oblique septum forming 

 separate cell c. iv. Subdivision of cell c into two cells by vertical 

 septum d. v. Further subdivision into four cells by transverse 

 septum e. vi. Two lower cells growing out into rhizoids//. 



embryo, and at the lower nodes of the sexual plant. The 

 nodes of the rooting system differ from those of the 

 stem- system (which will be described later) in being 

 much simpler in construction and being primarily 

 formed of the swollen ends of the long cylindrical cells 

 of which the root-system consists. 



The early stages in the formation of a root-node are 

 shown in Fig. 1 above. In the first place a curved 



