1899] XATURAL SCIENCES OF PHILADELPHIA. 89* 



There are but three lateral branchlets, though occa^ioually four; 

 and the retardiug of the axial growth has been of such a severe 

 character, that the axillary origin of the lateral branches has been 

 totally obscured. The pedicillate male flowers originate from 

 numerous axillary buds on these fruit-bearing branchlets, the 

 external evidence of such origin being also obscured. It is be- 

 lieved that a careful study as indicated will be convincing that it is 

 the degree of the rhythmic growth-force that decides the character 

 of the plant, and also the relation of the sexes to each other. 



Now let us take Sanicula Canadensis. With the light already 

 gained, we see that nothing but a variation in the force of the rhyth- 

 mic wave has made a distinct species. The characters are all of the 

 same class, but there has been acceleration and retardation of the 

 wave force in diflferent directions. The axillary branchlets haA'e 

 continued to retain the attention of the growth-wave to the last, 

 and now bear the female flowers — while the weaker central one has 

 accorded to it male ones only. Examining, now, the Old "World 

 species, Sanicula Eurojxea, we see scarcely any difference except 

 such as might occur from variation in the degree and direction of 

 the growth-wave. Nutrition has been diverted from the central 

 axis to a greater degree than even ia our own S. Canadenns. It 

 produces only short-stalked male flowers. 



We here have a genus in which we can clearly see how the 

 species were made. The degree of force exerted by the rhj^thmic 

 Avave started the process, and the assimilation of nutrition completed 

 the task. 



The study brings us nearer to a perception of the origin of 

 species. But we may not yet perceive the hand that set the process 

 in motion. The characters that distinguish these three species seem 

 permanent now. They do not change under any conditions of 

 environment existing at the present time, however varied they may 

 be. Though we may say that the three species would easily be 

 produced out of one type, simply by varying degrees of growth - 

 force; the couditious under which this variation occurred, and the 

 period in the world's history when they occurred and became 

 hereditary, is still a mystery. 



