SECT. IX. CAUSES OF DESCENT. 



conduct also the proper juice through the returning 

 vessels of the bark. In short if, with Saussure, we 

 admit the existence of a contracting power in the 

 former case sufficient to propel the sap from ring to 

 ring, it will be absolutely necessary to admit it also 

 inthe latter. Thus we assign a cause adequate to the 

 production of the effect, and avoid at the same 

 time the transgression of that most fundamental 

 principle of all sound philosophy which forbids us 

 to multiply causes without necessity. 



CHAPTER IV. 



PROCESS OF VEGETABLE DEVELOPEMENT. 



WHEN the sap has been elaborated in the leaf, and Different 

 converted into proper juice, it is now finally prepared d^eTo? 

 for immediate assimilation, and for the production P lants - 

 of such parts and organs as are peculiar to the 

 species, or necessary to the perfection of the in- 

 dividual. The next object of our inquiry, therefore, 

 will be that of tracing out the order of the deve- 

 lopement of the several parts, together with the 

 peculiar mode of operation adopted by the vital 

 principle. But this mode of operation is not 

 exactly the same in herbaceous and annual plants, 

 as in woody and perennial plants. In the former, 

 the process of developement comprises as it were 



