TREES GROWING NEAR WATER. 101 



the soil.' This opinion finds confirmation in the fact that 

 scarcely any other tree of our forests offers a greater resistance 

 to the force of storms under the most unfavourable soil con- 

 ditions. 



" On the other hand it is held that the function of the knees is 

 principally physiological by acting as organs of aeration. The 

 exposed parts of the knees effect the absorption, and by their 

 chlorophyll-bearing tissue, the partial decomposition of atmos- 

 pheric gases under the influence of light, and their trans- 

 mission to the sap of the roots, promote the process of 

 assimilation in parts of the tree debarred from a sufficient 

 supply of the same. 



"With the decay of the tree, the knees rot and finally disap- 

 pear ; the same is said to take place after the drainage of the 

 swamp. Not being needed they are not present in the trees 

 grown on high land. 



" From the fact that the knees serve the tree mechanically 

 by increasing the force of the tree to maintain its foothold in 

 a yielding ground and that further by their physiological 

 function the processes involved in its nutrition and growth 

 are promoted, it appears clearly that in the peculiar develop- 

 ment of the root system the cypress possesses the means of 

 adapting itself perfectly to the conditions of its immediate 

 surroundings." 



SOUTHERN WHITE CEDAR. {Plate XLV.) 



Chamcecyparis th^roides. 



Bark : light reddish brown ; very fibrous ; separating into loose scales. 

 Branchlets: brown, their thin bark also separating. Leaves: tiny ; simple ; 

 ovate and awl-shaped ; overlapping each other like scales and growing closely 

 together in rows of four, up and down the branchlets. Dull brownish or blue- 

 green ; glaucous. Cones : hardly one-half an inch wide; globose; sessile on 

 leafy branches ; purplish at maturity ; glaucous, and opening towards the centre 

 when ripe, not towards the base. Scales : thick ; several-pointed and as though 



