STKUCTURE AND DEVELOPMENT. 17 



Plate II. The first change which takes place after 

 fertilization is that the coarse starch-granules and oil- 

 drops, with which the oospore is filled, begin to recede 

 from the apical region, the part vacated becoming occu- 

 pied by light-coloured fine-grained protoplasm. A trans- 

 verse septum is then formed, separating the oospore into 

 two very unequal portions (PL II, f. 1). The upper 

 portion containing the protoplasm forms a small plano- 

 convex lens-shaped cell, the so-called nodal cell (a) 

 from which the young plant originates, while the 

 larger, lower portion (b) remains as a store-place of 

 reserve nutritive material. The nodal cell soon swells 

 and protrudes, the apex of the oospore-shell splitting 

 into five teeth to allow of this expansion (PL II, 

 f . 2) ; the protoplasm in the cell separates into two 

 portions, this separation being followed by the growth 

 of a second vertical septum, cutting the nodal cell into 

 two cells (PL II, f. 3). One of these cells goes to 

 form the pro-embryo, to be described later, the other 

 to form the primary root, using the term root in its 

 broad sense. Although it fulfils the functions of a 

 root in drawing food from, and anchoring the plant to, 

 the soil, the rooting system of a Charophyte has no 

 analogy in structure with that of a Flowering Plant, 

 consisting as it does merely of branching processes 

 formed of slender colourless thin-walled unicellular 

 filaments, similar to the rhizoids met with in the 

 Bryophytes, with more or less thickened nodes. The 

 term " rhizoids ' is used in referring specifically to 

 these filamentous structures. 



One of the two cells into which the 



R.OOt-Syst6Hl. 11 n f , i i- 



nodal-cell ot the germinating oospore 

 has become divided, and which has been referred to as 

 giving rise to the primary root, usually becomes sub- 

 VOL. i. 2 



