140 BOTANY. 



2. Sympodial dichotomy, in which one of the branches of each bifur- 

 cation develops more than the other. 



a. Helicoid sympodial dichotomy, in which the greater development 



is always on one side (Fig. 118, B). 



b. Scorpioid sympodial dichotomy, in which the greater develop- 



ment is alternately on one side and the other (Fig. 118, G). 



B. MONOPODIAL. 



1. Botryose monopodium, in which, as a rule, the axis continues ta 

 grow, and retains its ascendency over its lateral branches (Fig. 119). 



2. Cymose monopodium, in which the axis soon ceases to grow, and is 

 overtopped by one or more of its lateral branches. 



. Forked cymose monopodium, in which the lateral branches are 



all developed (Fig. 120, C). 



b. Sympodial cymose monopodium, in which some of the lateral 

 branches are suppressed ; this may be 

 b'. Helicoid, when the suppression is all on one side (Fig. 120, 



Z>); or 



b". Scorpioid, when the suppression is alternately on one side 

 and the other (Fig. 120, A and B). 



Dichotomous branching takes place in many Thallophytes ; it is 

 beautifully seen in the appendages to the perithecia of many Erysipha- 

 cese (e.g., lilac-blight, cherry- blight, etc.) It occurs also in the roots, 

 stems, and leaves of many Pteridophytes, and the leaves and other 

 phyllome structures of some Phanerogams. 



Monopodial branching is, on the other hand, the general rule for all 

 members of the plant-body in Phanerogams, and in Pteridophytes, 

 Bryophytes, and Thallophytes very much of the branching is also of 

 this kind.* 



II. STEMS. 



178. The primary stem of a plant first develops from the 

 meristem tissue of the embryo ; its subsequent growth is a 

 growth from the meristem of the punctum vegetationis, to- 

 gether with an intercalary growth of its neAver parts. On 

 account of the more rapid growth of its young leaves, it usu- 

 ally happens that the stem is terminated by, and appears to 

 grow from, a bud ; in fact, it is a common statement that 

 stems grow from buds. It will be necessary to examine the 

 bud in detail. 



* A full discussion of this subject would occupy more space than can 

 be allotted to it in this book, and any attempt to cover the subject in a 

 few pages would tend rather to confuse the student than to enlighten 

 him. For a good account, the student is referred to Sachs' " Text-Book 

 of Botany," p. 155 ; Hofmeister's " Allgemeine Morphologic der Ge- 



