ORGANS AND SYSTEMS OF ORGANS. 



179 



astichies," nor to the vertical rows or " orthostichies " (Naumann). 

 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. DIFFERENCE IN THE POWER OF DEVELOP- 

 MENT OF THE MEMBERS OF EQUAL MORPHO- 

 LOGICAL VALUE. CLASSIFICATION OF ORGAN- 

 SYSTEMS. 



(After NAGELI and SCHWENDENER.) 



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, By 

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



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 sympodium (C) the upper part 



