8 NOTES OX 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 

 iniluence of the other trees upon its functions. 



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

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

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

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

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

 ground with many forms with Avhich it no longer Avillingly groAvs. In 

 eocene and pliocene times it seems to liaA^e mingled its leaA^es in the forest 

 beds Avith the ancestors of our jioplars, beeches, Avalnuts, oaks, persimmons, 

 &c., &c. To-day Ave find none of the species of these genera groAving in 

 the same localities AA-here the Taxodium flourishes. It may be suggested 

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

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

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

 tion. The deposits noAv making in our cypress. SAA'amps do not contain 

 such minglings of the lea\'es of a Avide area as Ave find indicated in the 

 fossils of the Greenland miocene beds. If they Avere fossilized, Ave should 

 not find, as exploi'ers liaA^e found in the Greenland beds, the entire leaA'es 

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

 higher ground, mingled Avith tAvigs and leaA'es of the Taxodium in the same 

 square yard of space. 



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

 association betAveen the ancestral Taxodium and those of the other forest 

 trees AA'hose descendants noAv occupy the uplands alone, Avas 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 shoAV that the Taxodium 

 Avill 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, Avhile there 

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

 of SAvamp 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, 1868, p. 12. 



