OROANS AND SYSTEMS OF ORGANS. 



179 



asticliies," nor to the vertical rows or " orthostichies " (Naninann). 

 We can only say that the position of organs is dependent upon the 

 size, form, and the relative position of new organs and organs 

 already formed. The activity of the leaf-forming apex of the stem 

 is under the mechanical influence of organs already formed. The 

 fact that many leaf-beginnings with wide divergences really corre- 

 spond to the arrangement of the organs on the ground-spiral is not 

 contradictory to what has been stated. 



III. DIFFEKENCE IN THE POWER OF DEVELOP- 

 MENT OF THE MEMBERS OF EQUAL MORPHO- 

 LOGICAL VALUE. CLASSIFICATION OF ORGAN- 

 SYSTEMS. 



{^After Nageli and Schwendenek.) 



A system, as represented in Fig. 105, A, may be formed in dif- 

 ferent ways, and its difference as compared to other systems de- 

 pends upon the mode of development. We will distinguish two 

 forms of development, the monopodial and the sympodial. A 

 monopodium is formed according to the plan shown in Fig. 105, B \ 

 a sympodium according to the plan shown in Fig. 105, C. 



Fig. 105. (Diagramatic.) 



In the monopodium {B) the primary axis represents the median 

 line and grows most strongly, the lateral branches cease to grow 

 early, and do not branch. In the sympodimn ((7) the upper part 



