I 78 



BIOL OGICA L LEC Tl/RES. 



fact among gardeners that over-fed plants will often produce no 

 fruit. When pear-trees refuse to bear fruit, they can often be 

 made prolific by cutting away the central root, thus lessening 

 the supply of nourishment. As a rule, when plants are poorly 

 fed, they put forth blossoms and ripen their fruit earlier, 

 although it may be smaller and of poorer quality. 



(5) The influence of the sea upon plants is quite remark- 

 able. We have seen that in desert regions, and to some extent 

 in high altitudes, plants have greater or less tendencies to take 

 on consolidated forms. This is also true of seashore plants. 



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Section a. 



Plate No. 13. 



Section i>. 



The cause in both desert and mountain regions was a lack of 

 moisture. On the seashore, at the water's edge, and even 

 with many plants standing in the water, we find these thick- 

 ened leaves and leafless forms. Hence we must look for 

 another cause for this than lack of water. 



Ordinary land plants secure the water which they need 

 mostly through their roots. Although the soil may be appar- 

 ently dry, yet the plant has no difficulty in supplying its 

 necessities, for every particle of the soil is surrounded by a 



