i6 



is nearly always six; in Chara there may be as many as sixteen. The 

 peripheral cells of successive nodes are not exactly on a line, but each 

 node deviates by half the interval between the peripheral cells, so 

 that a regular spiral is produced ; in species with a large number of 

 leaves the divergence is small, with sixteen leaves a divergence of J^, 

 in Nitella there is usually a divergence of -^. When, as in most 

 species of Chara, the stem is corticated by longitudinal series of cells, 

 this divergence is easily seen, especially as the stems usually twist 

 more and more as they grow older, but in the naked species (Ni- 

 tellse and some Charse) the torsion is noticed only by means of the 

 clear line between the granules of Chlorophyll, the " indifferent line" 

 which marks the boundary between the up and down streams of 

 the circulating protoplasm ; this indifferent line seems to coincide 

 with the primary septum which divides the nodal cell into halves. 

 The direction of this divergence is to the right, upward. 



LEAF. The vegetative cell of the leaf arises from a peripheral 

 cell of the stem-node, but, unlike the vegetative cell of the stem, it 

 produces a limited series of nodal and internodal cells, nearly con- 

 stant in number for each species, and terminates by a tip, usually 



pointed, divided by sim- 

 ple septa into two or more 

 simple cells. The basal 

 node is somewhat com- 

 plicated in structure, since 

 it develops, in some spe- 

 cies, cells for stipules and 

 cortex, and even for ac- 

 cessory leaflets and spor- 

 angia. A clear under- 

 standing of this basilar 

 node of the leaf and of 

 the organs which de- 

 velop from it, is essential, 

 since the groundwork of 

 much of the classification 

 of Characese is founded 

 upon the variations of 

 these organs. 



The parent cell of the 

 basilar node (Fig. 18, 

 node on the side of the 



Fi 



p-b), swells and protrudes from 



