304 BOTANICAL GAZETTE [APRIL 
TABLE IV—Continued 
WIDTH OF WIDEST SPRING 
VESSELS 
Atlantic Pacific HABITAT 
WwW B WwW B 
Q. aquatica.....|...... OMe as Salen oa. Sandy borders of swamps; Delaware 
to Florida, Gulf States, Texas, 
ss Oklahoma, etc. 
(\ Mulienbensi:| 6.444)... fo ok Variable habitat; dry hills to deep 
> 
rich bottom lands and rocky banks 
of streams; Ontario to Columbia, 
N. Louisiana, Texas, etc. : 
8 a Ae nate oe Cie! eed ies ROS taes i eeareae Optimum soil is fresh (rather moist) 
loam in un i 
sa 
to gravelly ridges; Ontario to N. 
: Flori innesota, Texas, etc. 
©. bieotor: (3.3. rag Ei Reema ba a sty Sac tie aaa Borders ot streams and swamps; On- 
io ia and W. Mis- 
souri; does not extend so far south 
as Q. alba. 
Ages ven eee Borders of swamps and streams; 
Delaware to Florida, Gulf States, 
Kentucky, etc. 
Q. Michauxii....| 0.587]...... 
that in the deciduous species width of spring vessel is at least largely 
determined by systematic affinity and by available water supply; 
the spring vessels being narrower in species belonging to physically 
or physiologically drier places, and for the same type of habitat 
being narrower in black oaks than in white oaks. 
The points of significance in connection with the deciduous oaks 
are: 
1. Of the six species with narrowest spring vessels (0.338 
0.378 uw), four are Pacific species and characterized by drier climate 
than the Atlantic species. Among the four Pacific species, the oné 
with the narrowest vessels is the one whose soil is definitely stated 
to be dry gravel. The second is subtropical in the region of ever- 
green species, and itself approaches the evergreen stage. cL 
habitat (apart from the Pacific climate). Of the two Atlantic 
species, one occupies an edaphically dry habitat, while the other, 
though variable as regards habitat, shows a power of living 0? at 
least rather dry sites. 
