VEGETABLE ORGANIZATION. 81 



of vegetable life. The stems of the grasses are 

 hollow tubes ; their most solid parts, which 

 frequently consist of a thin layer of silex, occu- 

 pying the surface of the cylinder. Of all the 

 possible modes of disposing a given quantity 

 of materials in the construction of a column, 

 it is mathematically demonstrable that this is 

 the most effective for obtaining the greatest 

 possible degree of strength.* 



The graceful continuous curve with which the 

 stem of a tree rises from the ground, is the 

 form which is best calculated to give stability 

 to the trunk. Evidence of express mechanical 

 design is likewise afforded by the manner in 

 which the trunk is subdivided into its branches, 

 spreading out in all directions, manifestly with a 

 view to procure for the leaves the greatest extent 

 of surface, and thus enable them to receive the 

 fullest action of both light and air. The branches, 

 also, are so constructed as to yield to the irre- 

 gular impulses of the wind, and again, by their 

 elasticity, to return to their natural positions, 

 and by these alternate inflexions on opposite 

 sides, to promote the motion of the sap in the 

 vessels and cellular texture of the liber and 



* Galileo, the most profound philosopher of his age, when 

 interrogated by the inquisition as to his belief in a Supreme 

 Being, replied, pointing to a straw on the floor of liis dungeon, 

 that from the structure of that object alone he would infer with 

 certainty the existence of an intelligent Creator. 



VOL. I. G 



