STRUCTURE 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 



nodal-cell of 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 



