LEITNERIA FLORIDANA. 73 
tion of climate favoring the northward extension of a 
subtropical flora over the region.* 
It seems probable, therefore, that Leitneria and the 
species of the Floridan flora which accompany it in the 
Missouri swamps, represent the remnants of a warm tem- 
perate swamp flora which at one time extended continuously 
in the low lands, around the coast and up the river, from 
Florida to the upper limits of the present deep swamps; 
and that they are now likely to be found in such situations 
at any point between the extremes, where the original 
conditions have remained little or not at all changed by the 
general drainage which has been progressing at least for 
the last few centuries. One of the most promising fields 
for botanical exploration in the eastern United States, and 
one of the least known, is the swamp region of the lower 
Mississippi Valley and the Gulf Coast; and I have little 
doubt that a fuller knowledge of the flora of this region 
will not only confirm the explanation here offered of the 
occurence of Leitneria in Missouri, but extend its known 
range from this point to its original locality in Florida. 
Unless there is an error in the label of Drummond’s speci- 
men, it should also be found in similar situations across 
Louisiana and around the Gulf in Texas. 
Mr. Bush’s attention was first called to the occurrence 
of Leitneria in Missouri by the frequent mention in the 
swamps of avery light ‘‘ cork wood,’’ greatly surpassing 
even young tupelo (Vyssa) in buoyancy, and much used 
by fishermen for floats on their nets; and the trunks which 
he placed in my hands were of such surprising lightness 
that I requested my friend Professor Nipher to determine 
the specific gravity of the decorticated wood. An exam- 
* The results of Professor Call’s work, here briefly outlined from his 
letter, are to be found in the Proceedings of the Iowa Academy of 
Science, 1887-9, 52, 85, and more fully, as volume ii. for 1889 of the 
Reports on the Arkansas Geological Survey. See, further, a paper by him 
in Amer. Journ. Sci. and Arts, 1891, xlii. 394, on the fossil woods of this 
region, also considered in his larger report. 
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