MASS OF THE EARTH. 47 



Poisson has further attempted to show that this 

 force of endosmose may be considered as a parti- 

 cular modification of capillary action. If these 

 views be true, we have here two mechanical 

 forces, capillary action and gravity, which are 

 adjusted to each other in the manner precisely 

 suited to the welfare of vegetables. 



2. As another instance of adaptation between 

 the force of gravity and forces which exist in the 

 vegetable world, we may take the positions of 

 flowers. Some flowers grow with the hollow of 

 their cup upwards: others, "hang the pensive 

 head" and turn the opening downwards. Now of 

 these " nodding flowers," as Linnaeus calls them, 

 he observes that they are such as have their 

 pistil longer than the stamens ; and, in conse- 

 quence of this position, the dust from the anthers 

 which are at the ends of the stamens can fall 

 upon the stigma or extremity of the pistil ; which 

 process is requisite for making the flower fertile. 

 He gives as instances the flowers campanula, 

 leucoium, galanthus, fritillaria. Other botanists 

 have remarked that the position changes at dif- 

 ferent periods of the flower's progress. The 

 pistil of the Euphorbia (which is a little globe or 

 germen on a slender stalk) grows upright at first, 

 and is taller than the stamens: at the period 

 suited to its fecundation, the stalk bends under 

 the weight of the ball at its extremity, so as to 

 depress the germen below the stamens : after 



