1 68 BIOLOGICAL LECTURES. 



It will be observed, too, that there are no signs of knees 

 underneath. 



Plate No. I represents a water form from the James River. 

 The base, in this form, is always very much enlarged. This 

 enlargement is a part of the aerating system needed to secure 

 the necessary oxygen, and is, of course, entirely absent from 

 the land form. 



The departure from the sharp, cone-like form natural to the 

 conifers, is due to the difificulty in obtaining both air and food 

 from the water. This lack of nourishment shows itself in the 

 dwindling, depauperate and dying branches of the upper part, 

 since that part is most remote from the food supply. 



In some of the lakes of Southern Florida it now and then 

 happens that a cypress tree has obtained a foothold in much 

 deeper water than is its normal habit. Here all of these water 

 peculiarities are greatly exaggerated. The trunk of the tree 

 produces an immense cone, the top of which points up to the 

 surface of the water and ends with a few flat sprayey branches. 

 The base of the cone may be forty or fifty times the diameter 

 of the top, from which come the few straggling branches which 

 project above the surface of the water. There are at its base 

 innumerable knees. In a tree having the height of twenty- 

 five or thirty feet, the cone below the water will represent a 

 little over one-half, and the branches above the other half of its 

 altitude. Plate No. 3 represents such a tree in South Florida 

 after the waters of the lake had been drained away. The 

 knees, being of no further use, quickly rotted and disappeared 

 and are not shown in the photograph. Originally the water 

 was high enough to touch the lower branches, and the tree 

 eked out a miserable existence, struggling hard in the deep 

 water for both air and food. The difficulties under which 

 it labored developed it into a great monstrosity. It is an 

 extreme expression of excessive water supply. Conij^are its 

 short, cone-like trunk, entirely immersed in water, with what 

 may be called the normal development now found only in 

 our parks (Plate No. 2). In this form the trunk is tall and 

 slender, with branches towering to a very sharp point. The 

 water form has acquired its knees and greatly enlarged 



