In the tree, the main trnnk is the axis of growth ; 

 the l)ranches diverge from this axis under the same 

 hiw which sends the molecules of water on their di- 

 vergent paths of crystallization. Each Ijranch of the 

 tree has its special axis, from which the minor hranches 

 diverge ; and leaves ray from the branch as the branch 

 rays frou) the stem, the ribs of the leaf following the 

 same general law of divergence. In the plant we see 

 the action of centripetal and centrifugal forces, con- 

 trolled l)v (Jrowth Force. 



A large proportion of the Protozoans and Radiates 

 resemble crystals in form. Some of them, especially 

 among Rhizopods, are strikingly similar to crystals. 

 The limbs of animals correspond to the branches of 

 plants. They bud at right angles to the axis of growth, 

 but may be modified so as to ))ecome parallel with it, 

 as in the lower extremities of man. 



In the Groups of animals, as well as in the individ- 

 ual forms, we lind evidence of the operation of the 

 same laws. There is a well-defined axis, and there is 

 a circle of radiation in every great group. The branches 

 of such groups are related to each other by characters 

 which make it impossible to confound them with mem- 

 bers of a higher circle. 



These circles — or, more accuratelv, coils of ascendino; 

 spirals — represent the disposition of the rays of a 

 color disk, the plane of crystallization of a water-crys- 

 tal, the Ijranches of trees, the disk of a flower, the 

 seeds of a fruit, the symmetrical parts of a radiate 

 animal, — all alike due to the great law of Phyllotaxis, 

 resulting from the dual action of the centripetal and 

 centrifnu'al forces in nature. 



