Berlin, 1862," we are greatly 

 indebted. The apical cell 

 (vegetative cell) of the new 

 shoot throws off from its base 

 a series of cells by repeated 

 horizontal division. The api- 

 cal cell itself remains plano- 

 convex, and when its energy 

 is exhausted, persists as a 

 terminal cell of the same form. 

 Each cell that is thrown off 

 from the base of the apical 

 cell divides immediately, by 

 horizontal fissation, into two 

 unequal cells, the lower shal- 

 low and bi-convex, the upper 

 deeper and bi-concave. The 

 lower of this pair elongates 

 without farther division and 

 becomes a long internodal 

 cell, often attaining a length 

 of several inches (internodal 

 cells six to eight inches long 

 are not uncommon in lake 

 forms of Nitella megacarpa, 

 Allen). The upper bi-con- 

 cave cell of the above pair 

 forms a stem-node as follows : 

 Soon after its appearance it 

 divides, by vertical fissation. 

 into two equal halving cells 

 (see Fig. 13). In each of 

 these half cells a series of pe- 

 ripheral cells arise, by excen- 

 tric division and in regular 

 order, beginning first on one 

 side of the septum, then on 

 the other, and proceeding in 

 alternation till the circle is 

 closed. These peripheral cells 

 are the starting points of an 

 equal number of leaves. In 

 Nitella the number of leaves 



