38 



strictest sense. The peripheral cells are the mother-cells of just so 

 many leaves. The nmnber of these cells, and of leaves in a verticil, 

 amounts in most Nitellae regularly to six (very seldom five) and in 

 Chara mostly to eight or ten, or even to fourteen or more. The leaves 

 of successive verticils alternate with each other; for the halving- 

 septum of each succeeding node forms an angle with that of the pre- 

 ceding, equal to a half interval of a verticil, so the position of the 

 first leaf of each successive vertical deviates a half interval from that 

 of the first leaf of the preceding verticil. In this way a definite pre- 

 cession is established ; the first leaves of the verticils forming a spiral 



with small divergence (yV> i*^-, tV, etc.). This spiral is always to the 

 left (downward, T. F. A.) ; and in this direction, with the increasing 

 tension of the internodes, a more or less noticeable torsion of the stem 

 takes place, most distinctly seen in corticated species ; in the naked 

 species marked by the oblique course of the chlorophyll granules and 

 indifferentiated striae (indifferenz-streifen) as well as by the direction 

 of the circulation." (A. Braun.) 



Fig. i^, of the same plate, represents a stem-node of Chara coronata^ 

 as seen from above, without the leaves. Each of the peripheral cells 

 develops a leaf, as follows : the cell divides into two unequal portions 

 by a horizontal septum, the lower and smaller segment remains in 

 the node, while the upper divides into a " globular complexity " of 

 cells, protrudes from the node and forms the basilar node of the leaf. 

 This node consists of central and peripheral cells. The peripheral 

 cells divide parallel to the surface of the node-disk, giving rise to 

 superposed marginal cells; the lozuerinarginal cells give rise to the cor- 

 tex-cells of the stem ; and the upper develop usually somewhat on either 

 side of the lower and give origin to the stipules. Usually there are 

 two stipules at the base of each leaf, one on either side, but in Ch. 

 ceratophylla there is a third stipule developed from a cell arising be- 

 tween the other two. In Ch, coronata one of the lateral stipular cells 

 fails to develop and but one stipule is seen, so that the stipules seem 

 to alternate with the leaves. In Lychnothamnus Wallrothii the stip- 

 ular cell remains directly in the centre, and the stipule is exactly op- 

 posite the leaf, no cortex being developed. Chara stelligera^ possess- 

 ing neither stipules nor cortex, exhibits at the base of the leaf three 

 insignificant cells, protruding slightly. In Nitella and Tolypella we 

 find no trace of cortical or stipular cells, though now and then ac- 

 cessory, simple, leaf-like formations remind one of stipules. In N, 

 hyalina these are numerous, arising from the base of the leaves in 

 pairs, externally or even internally. 



■ The cortex-cells, arising from the basilar node of the leaf, behave 

 in a manner quite similar to the primary cells of the stern. They 

 consist of alternate, elongated and nodal cells ; the former elongating 

 as the stem elongates, the latter not elongating, but forming a node 

 which develops a wart or spine and lateral cells.' 



I.— Some species of Chara never develop these cortex-tubes, and 

 the stems remain naked, like those of Chara coronata, Ziz. 



2.— Some species develop a simple cortex-tube, which is so small 

 that it does not join the one from the next leaf, as Chara inconnexa, 

 Allen. 



