RHYTHM. 229 



trajectory paths, and what may such paths and intersections 

 possibly mean from a physical standpoint — that is to say, to 

 what extent may the diagrams be also taken as the expression of 

 a field of distribution of growth-energy, comparable, for example, 

 to manifestations of distribution of the physical energy of the 

 electro-magnetic field ? 



To what extent one may be justified in thus passing from a 

 kinematic to a kinetic standpoint is, of course, very questionable ; 

 and similarly little can be said beyond mere speculation until 

 miore is known as to what is actually meant by the expression 

 growth-energy, or the energy of life, and how far it is comparable, 

 for example, with "electrical" energy. One point may, however, 

 be conceded : that in the case of living matter, the actual mechani- 

 cal energy accompanying life obeys -physical laws just as surely as its 

 material substance obeys chemical laws. 



The data afforded by the plant are these : — 

 I. A growing, expanding system, containing, therefore, moving 

 particles ; in which 

 II. Growth-energy is being introduced from a central "grow- 

 ing-point " ; and 



III. A construction which, as expressed in the transverse com- 

 ponent of the formation of lateral members, has been 

 put forward as implying primarily the geometrical pro- 

 perties of orthogonal trajectories. 



How far, then, can analogues be found for such a system in the 

 domain of physics ; and how far is it possible to press such an 

 analogy, as indicating some fundamental law of protoplasmic 

 growth ? 



Further, in the discussion of symmetrical and asymmetrical 

 phyllotaxis (cf. Part II.), it became increasingly evident that, while 

 the hypothesis of a single controlling ontogenetic spiral gives no 

 satisfactory clue to the general phenomena of all varieties of 

 phyllotaxis, all such systems might be readily interpreted and 

 discussed in terms of series of intersecting curves — the contact- 

 parastichies. These curves should, therefore, have some meaning 

 attached to them. If, as the log. spiral theory suggests, these 

 curves imply lines of equal distribution of growth-energy, it may 



