PHANEROGAMIA : AXIAL ORGANS. 221 



The direction of the root varies very much, often with specific regu- 

 larity ; but most of what was formerly included here belongs to the 

 axis (in the strict sense). One peculiarity is interesting in its relation to 

 the axis. In the germinating embryo the basis of the root soon becomes 

 a fixed point in the soil, the elongatory root proceeding downward 

 from this, through the earth. In rare cases, in loose mud with a firm 

 substratum, on the other hand, the point of the root very soon becomes 

 the relatively fixed point, from which the elongating root gradually lifts 

 the whole plant upward. This may sometimes be observed in solitary 

 bog-plants. From the descriptions, this is probably the cause, depending 

 upon the locality, of the peculiarity of the so-called Mangrove woods on 

 the shores of the rivers of tropical Africa and America. The peculiar root- 

 ing of some Palms, e. g. Areca oleracea, in which a number of adventitious 

 roots, springing out almost on one level from the base of the stem, lift up 

 this base a certain height free from the ground and retain it there, de- 

 pends upon the same cause. The light sandy soil does not give the base 

 of the root hold enough to allow a rapid penetration of the apex into 

 the earth, thence at least part of the elongation only removes its base, and 

 with this also the base of the stem, from the apex, consequently lifts 

 it upward, perhaps till the weight of the stem itself affords a sufficient 

 resistance. One might call it an organic example of the relativeness of 

 all rectilinear motion. 



The arrangement of the branches in relation to each other present 

 manifold variation, which, for the most part, depends on the varied 

 position of the branches upon the main root, and their different amount 

 of development. 



The preponderating development of parenchyma in certain places 

 produces either mere inequalities of the surface, in the simplest cases 

 papillae, the so-called radical hairs (fibrils) in moist, loose soils, or con- 

 siderable expansions above, below, in the middle or throughout the whole 

 length. By the formation of wood, the root of the Dicotyledons comes 

 wholly to resemble the stem ; I will give the necessary explanations 

 thereupon under that head. This one may well enough name with the 

 otherwise wholly useless term caudex. 



B. AXIAL ORGANS. 



a. Of the main Axis (Axis primarius), or the Axis of the simple Plant 

 (of the second Order}. 



126. The axis which is produced from the embryo is called the 

 main axis (axis of the simple plant) ; those produced from buds, 

 secondary axes. 



At the very outset of the consideration of the formation of axes, 

 we must premise that all, according- to the specific peculiarity of the 

 plant, live either during one summer only (one period of vegetation, an 

 annual axis), or have a longer duration (perennial axes). The former 

 I especially distinguish by the term stem (caulis in the strict sense), 

 the latter I call trunk (truncus). The former, again, live only for the 



multiceps and prccmorsa, both true stems, among roots. Trcviranus (Physiologic, vol i. 

 p. 367.) still treats of bulb and tuber among the roots. 



