THE STEM. 39 



points the stem is continuously lengthened in one direction ; by the deve- 

 lopment of lateral ones from below upwards (acropetal) it becomes 

 branched. This mode of growth is called monopodial (tig. 27). 



Dichotomy. In some instances (e. y. the tendrils of some vines, the roots 

 of Lycopod's, and frequently in Cryptogams) the terminal growing-point 

 bifurcates. Each pair of new shoots so formed is then of the same degree or 

 order, because each is formed from the same original growing-point and at 

 the same time. The growing-point may, in this manner, divide into several 

 divisions of the same generation or relative order. The shoots formed 

 dichotomously, as above explained, are monopodial or indefinite as to their 

 ramification, and may grow equally and regularly, or the growth may be 

 arrested in certain of them, and hence may arise much difference in the 

 appearance of the mode of branching. 



Dichasium. In the foregoing illustrations the terminal growing-point 

 either continues to lengthen as growth goes on, or it divides into divisions 

 of equal degree, though often of unequal vigour. But it very commonly 

 happens that the terminal growing-point or bud ceases to grow after a 

 time (figs. 28, 29). This may happen accidentally or from the effects 

 of frost or other injury, however caused, or it may occur constantly 

 and naturally, as in many trees, e. g. the Lilac (fig. 29). When arrest 

 of growth in the terminal bud takes place in the manner just indicated 

 the lateral buds often grow so vigorously, and are so closely placed, 

 that they appear to radiate from the same point as if they were formed 

 by dichotomy of the terminal growing-point. This false or apparent 

 dichotomy is sometimes called a dichasium or false cyme (fig. 28). 



Sympode. When in the case of a dichotomous ramification one of the 

 divisions grows more vigorously than the other, or, which amounts to the 

 same thing, when one of them is arrested in its growth or altogether sup- 

 pressed, then, although the two divisions are of equal degree and age, yet 

 the stronger of the two presents the appearance of and grows in the same 

 direction as the primaiy shoot, while the smaller one is often pushed on one 

 side, so as to look like a lateral shoot of a subordinate degree (fig. 38). The 

 appearance may thus be that of a continuous shoot formed by the extension 

 of one growing-point and giving off lateral branches ; but in reality the 

 shoot is not the result of the extension or bifurcation of on growing-point, 

 but of a number of growing- points of different generations formed in suc- 

 cession one after the other. In this way what is called a sympode is pro- 

 duced, and ramification so characterized is sympodial. This arrest of 

 growth may take place regularly or irregularly, producing corresponding 

 variations in the form of the ramifications : thus, supposing a branch to 

 divide into a number of subdivisions by repeated bifurcations to the right 

 hand or to the left respectively, it may happen that all the shoots on the one 

 side are arrested in their growth as compared with these on the other. Or 

 it may happen that the arrest of growth may take place first on one side 

 arid then on the other in regular alternate order. All these modifica- 

 tions may be seen in the mode of branching in various cellular Cryp- 

 togams as well as in higher plants. 



Characters of the Stem and Branches. In the description of stems 

 and branches generally, certain technical terms are in use, in addition to 

 those above explained. These refer principally to a. consistence ; b. direc- 



