304 BOTANICAL GAZETTE. | Nov., 
ducts much larger (.050-.090 mm.): leaves (mostly 4) shorter 
and much thicker. 
S. California and southward into Lower California. 
In reference to this whole group of “nut pines” (the last five species) Dr. 
Engelmann’ says “it is an open question whether these species may not prop- 
erly be united into one, as the difference of flowers and fruit is very slight, and 
that of foliage is only relative.” We have been able to separate them upon the 
characters given, but do not claim that they should be kept specifically distinct. 
It is evident that they are very closely related, and if the differences noted do 
not serve to make them specifically distinct they will all have to be included 
under one species. For the present it seems better to keep them separate. 
++ ++ Dorsal side of leaf about as broad or narrower than either ven- 
tral: cuticle often much thickened, and stomata very deeply set: leaves in 
fives. 
13. P. Balfouriana Murray. Strengthening cells about two 
layers, sometimes three in the angles, very few in fibro-vascular 
region: ducts dorsal, two (.040-.080 mm.), always completely sur- 
rounded by strengthening cells, position as in P. cembroides, or 
nearer the middle, sometimes parenchymatous: leaves 1-1} in. 
long. 
Mountains of California. 
14. P. aristata Engelm. Resembling the last, but strength- 
ening cells fewer, but one layer next the epidermis, sometimes 
two on the dorsal side or at the angles, and an incomplete sheath 
or none at all about the ducts: dorsal ducts one or two, smaller 
(.025-.050 mm.), near the middle of the dorsal face, often quite 
close together: leaves as in the last. 
Mountains of Colorado, Arizona and westward. 
In Bot. Wheeler’s Report, p. 375, Dr. Engelmann reduces this species to a va- 
riety of P. Balfouriana. Judging from its leaf structure it should be restored 
to specific rank, for it is more distinct than many that are kept separate, and 
its superficial characters confirm this claim. 
at 2. Fibro-vascular bundles two: ducts mostly parenchymatous or inter- 
nat 
* Duets parenchymatous (mostly peripheral in P. resinosa). 
+ Bundle-sheath thick-walled (except sometimes in P. Sabiniana) 
++ A thin-walled layer next the epidermis. 
= Leaves in pairs. 
T Trans. St. Louis Acad. IV. 178. 
Lic. 
