oF TAXODIUM DISTICHUM AND RELATED SPECIES 395 
taining a luxuriant growth of various Nymphaeaceae and other 
Strictly aquatic plants. 
At every point. where Zaxodium imbricarium has been observed 
all the indications are that both the Lafayette and Columbia forma- 
tions are present, though of course I have been. able to actually 
verify this only in comparatively few cases. 
The cause of the preference of these two species of Zaxodium 
for different superficial formations is as yet unknown, but the com- 
parative imperviousness of the Lafayette clays doubtless has 
something to do with it. 
If my theory is absolutely correct, these two species would 
never be found together. One or two exceptions to this have been 
noted. On July 13, 1901, I found both species together in a swamp 
in the pine-barrens in the northeastern part of Lee county, Geor- 
gia. But it is noteworthy that the specimens of 7. distichum ap- 
peared stunted and unhealthy, while those.of 7. zméricarium were 
of the usual size and appearance. One explanation of their occur- 
rence together might be that the seeds of 7: distichum had been 
brought there in some manner and that the trees had managed to 
grow in spite of the unfavorable environment. I did not notice 
any fruit on these specimens of 7. distichum, and the species is 
perhaps not reproducing itself at this locality. A similar or anal- 
ogous state of affairs may prevail at the locality in North Caro- 
lina mentioned above, where Mr. Croom observed both species 
growing together. 
It might be remarked here that there has been some differ- 
ence of opinion among geologists as to whether the Lafayette for- 
Mation extends beneath the Okefinokee Swamp in southeastern 
Georgia. If my theory is true this question could easily be set- 
tled by a determination of the species of Zaxodium inhabiting the 
Swamp. So far as I know no botanist has yet penetrated this vast 
swamp, but there can be no doubt that it contains at least one of 
the species of Zaxodium, for cypress timber is said to be one of 
its principal resources, and the chief cause of the destruction of 
the swamp which is unfortunately now in progress. 
In addition to the influence of the Lafayette and Columbia 
formations on the distribution of these two species, the older under- 
lying strata also seem to have a considerable influence, For in- 
