4 NOTES ON THE BALD CYPRESS. 



themselves to the height of from two to ten feet, and are well above the 

 level of the swamp waters ; they then increase in diameter, while they cease 

 to grow in height. Their tops lose their conical shape, and become knotty, 

 or carunculated. During the process of growth, the summits of these 

 knees are exceedingly bud-like and vascular, always presenting a consid- 

 erable surface of fresh bark. The rupturing of the outer bark layers, as 

 the growth goes on, serves to give the bulbous top of the knee the look 

 of an opening bud. The gnarled and knotty growth of the old knees, 

 which have ceased to increase in height, serves also to expose the fresh 

 inner bark over considerable surfaces of the carunculated head that crowns 

 the knee. 



The height of these knees varies a great deal with the different positions 

 occupied by the trees that bear them. Generally they do not rise more 

 than two or three feet above the level of the main root ; but at times they 

 rise to four or even ten feet above its level. Observation has led me to 

 believe that the height of the knees is in good part determined by the aver- 

 age height of the waters in the swamp, the knees endeavoring to attain a 

 level which will bring their more vascular parts above the surface of the 

 water as it stands in the season of most active growth of the tree, which 

 occurs between April and July. If we take any swamp area occupied by 

 these trees, and examine carefully the development of the cypress in its 

 various jiarts, we shall see the evidence bearing on this point. In the first 

 place, we shall find the cypress on the higher grounds, near the edges of the 

 swamp, which are not overflowed save in the winter season, growing with 

 fair luxuriance, but quite without knees. The small tubercles along the 

 roots may be visible on close inspection, but they do not rise above the bed 

 of leaf mould. As we go into the wetter parts of the swamp, these knees 

 begin to appear; but it is only when the water stands a good part of the 

 year about the roots that they become a striking feature. The deeper we 

 penetrate into the swamp, the higher the knees rise above the surface of 

 permanent water, and the more abundant they are about the trees. In all 

 eases the top of the knees, when their upward growth is complete, rises 

 above the level of the ordinary spring and summer flooding of the swamps. 

 One other fact is needed to complete the chain of evidence. Whenever the 

 level of the swamp water is raised above the top of their knees, the trees 

 die, A very conspicuous instance of this is afforded by the extensive 

 tracts of land which were flooded by the subsidences that accompanied the 



