Introduction to Botany. 



pointing upward, but as the root grows forth it turns sharply 

 downward, and the shoot as it develops, sharply upward. 



This is brought about by the in- 

 fluence of gravity. 



In just what way gravity can 

 exert such an influence is not 

 known. We are accustomed to 

 think of gravity as invariably at- 

 tracting bodies toward the cen- 

 ter of the earth, but on living 

 and growing bodies it may exert 

 an influence of quite another 

 character. We might conclude, 

 without an experiment, that 

 gravity is the directive force ; 

 for whether seeds are germinat- 

 ing near the poles or at the 

 equator, the roots always turn 

 end view toward tfte center of the earth, 

 of the " cocoanut " or stone of the and the shoots away from it. It 



fruit (corresponding to the stone i -, 



of a peach), showing the dividing 1S > however, a simple matter to 

 lines of the three carpels which eliminate the directive influence 



compose the fruit. The embryo r . , , -, 



emerges through the lower open- f g ra Vlty, and by observing the 



ing. B, longitudinal section growth of seedlings under such 



through the fruit of the cocoanut, 



showing the embryo in process of circumstances to determine what 

 germination ; e, the stone sur- effect gravity is producing under 



rounding the fleshy endosperm; ... _. 



/ the enlarging cotyledon. The normal Conditions. Figures / 



plumule is growing upward anc j g illustrating the result of 



through the fibrous outer coat 



of the fruit. This coat is re- Experiment 41, page 15, show 



moved before the cocoanuts are how the i n fl uen ce of gravity may 

 marketed. After WARMING. * 



be demonstrated by removing it 



from one set of seedlings while it is still operative on 

 another set. 



rIG. o. 

 Fruit of the Cocoanut : 



