8 NOTES ON THE BALD CYPRESS. 



trees. Trees fifty years old have there attained a height of sixty feet and 

 a diameter of eighteen inches. We must ascribe its incapacity to maintain 

 itself in the existing forests of the Mississippi Valley to some unknown 

 influence of the other trees upon its functions. 



In the miocene and pliocene times this genus was one of the most wide- 

 ranging of all the forest-trees. Oswald Heer cites it from Switzerland. 

 Germany, Austria, France, Italy, Spitsbergen, Siberia, Kamtschatka, and 

 the Alutian Islands.* The circumstances in which we find its remains in 

 these ancient formations are such as to make us suspect that it shared the 

 ground with many forms with which it no longer willingly grows. In 

 eocene and pliocene times it seems to have mingled its leaves in the forest 

 beds with the ancestors of our poplars, beeches, walnuts, oaks, persimmons, 

 &c, &c. To-day we find none of the species of these genera growing in 

 the same localities where the Taxodium flourishes. It may be suggested 

 that the fossil remains we find are those of species that did not occupy 

 the same stations, but were brought together by floods in their common 

 burial places. I do not think that this hypothesis explains their associa- 

 tion. The deposits now making in our cypress swamps do not contain 

 such minglings of the leaves of a wide area as we find indicated in the 

 fossils of the Greenland miocene beds. If they were fossilized, we should 

 not find, as explorers have found in the Greenland beds, the entire leaves 

 of beeches, persimmons, and half a dozen other forms that now belong on 

 higher ground, mingled with twigs and leaves of the Taxodium in the same 

 square yard of space. 



It seems to me that we are led by these facts to the conclusion that the 

 association between the ancestral Taxodium and those of the other forest 

 trees whose descendants now occupy the uplands alone, was once much more 

 intimate than it is at present. This intimacy of association may have been 

 brought about by the less definite limitation to particular stations of the 

 trees that made up our ancient forests, or by the greater range of the Tax- 

 odium in the olden days. As experience goes to show that the Taxodium 

 will still live and flourish on a great range of soils, and that it does not 

 require access to moisture more than most of our forest trees, while there 

 is good reason to believe that the other forest trees are much less tolerant 

 of swamp conditions, I am disposed to think that the greater part, at least, 

 of the change of habits has been in the cypress itself; that it has gradually 



•Flora Fossiles Arctica: Zurich, 1808, p. 12. 



