STEU.CTUM1 AND DEVELOPMENT. 19 



diagonal septum (a) is formed, giving the ends of each 

 of the two cells a characteristic shape, which has been 

 likened to that of the human foot, the two "feet" 

 pointing in opposite directions and the surfaces repre- 

 senting their " soles " being in contact. The "toe"- 

 end of one of the feet swells (&), further septa (c, d, e) 

 ■are successively formed, and the separate cells grow 

 out into rhizoids (/). 



The root-nodes often become much thickened by the 

 production of a great number of cells containing 

 reserves of starch. These will be referred to later 

 under the head of bulbils. The rooting system, being 

 devoid of chlorophyll, is colourless. 

 Pro emb o ^^® other portion of the nodal-cell of 

 the oospore, which goes to form the 

 pro-embryo, grows outwards as a cylindrical process, 

 soon taking an upward direction (PI. II, figs. 4, 5, 6, 

 7 p), and, in contrast to the rooting system, becomes 

 green, chlorophyll being present at an early stage. 

 Horizontal septa soon arise cutting off portions from 

 below the growing point, the order in which division 

 takes place being shown in PI. Ill, figs. 7-9. The 

 cylinder then presents a longitudinal row of cells. If 

 we examine these cells in order we shall find that the 

 lowest is elongated and undergoes no division. The 

 second is very short and lenticular, and forms the 

 pro-embryonic root-node (PI. Ill, figs. 1, 2, 3, 9-12 rn.), 

 vertical division taking place as shown in Fig. 2 (p. 20). 

 From this node a number of rhizoids are produced, 

 and sometimes one or more accessory pro-embryos. 

 An elongated undivided internodal cell (PL III, figs. 

 1-4, 9-12 i.) succeeds the root-node, then a second 

 node (wn.) from which the pro-embryonic whorl is 

 produced. This is surmounted by a cylindrical process 



