STRUCTURE AND DEVELOPMENT. 31 



present (iii-vi), the upper row takes an upward, the 

 lower a downward direction, and the number in each 

 circle is normally double that of the branchlets. 

 When there is only one circle, the stipulodes in some 

 species grow upwards (i), and in others downwards (ii), 

 and the number may be either the same or double that 

 of the branchlets ; when the same number, they may 

 alternate with (i), or be opposite to the branchlets (ii). 

 In luxuriant states of species producing two circles, it 

 occasionally happens that a third circle is found grow- 

 ing outwards between the upper and lower circle. In 

 a very few species the development of the stipulodes 

 is irregular, and very rarely a ring of stipulodes is 

 produced above the branchlets. The stipulodes origi- 

 nate from the node at the base of the branchlets (see 

 Fig. 5 s., p. 24). 



In most of the Charese, all but the 

 cortex lowest internodes of the stem are com- 

 pletely covered with a sheath of cells 

 styled the cortex. This sheath consists of a number 

 of longitudinal row^s of cells which are in almost all 

 species contiguous. Two rows of these cortical-cells 

 originate from certain cells belonging to the node at 

 the base of each branchlet, one taking an upward the 

 other a downward direction, and adhering respectively 

 to the internodes of the stem above and below the 

 node from which the branchlet proceeds (Fig. 5, p. 24). 

 In this way the cortex of each internode is the joint pro- 

 duction of the two adjacent nodes, the ascending rows 

 of cortical cells of the lower node meeting the descend- 

 ing row^s of the node above it about the middle of the 

 internode ; the apical cells of the two series being 

 tapered at the end slightly overlap laterally. 



Where a branch is produced, one ascending row of 



