306 BOTANICAL GAZETTE. [Nov., 
19. P. Coulteri Don. Strengthening cells larger than the epi- 
dermal cells, in the cortical region broken into heavy bundles 
y the frequent rows of stomata; sometimes about the ducts ; 
very numerous in fibro-vascular region on both sides : ducts 4-10, 
quite variable in size (.025-.100 mm.), sometimes internal: leaves 
6-12 in. lon 
Along the Pacific coast. 
20. P. ponderosa Doug]. Strengthening cells smaller than 
epidermal cells, in 1 to 3 rather regular rows in the cortical re- 
gion ; also about the ducts: ducts mostly two, often five or more, 
quite variable in size (.030-.070 mm.): leaves 5-11 in. long. 
Generally distributed throughout the Rocky Mountains and westward. 
31. P. tuberculata Gordon, may be looked for in this group. 
= = = Leaves in fives: ducts always 3, one in each angle. 
21. P. Arizonica Engelm. of S. Arizona, and 
‘ Montezume Lamb. of Mexico, can not be separated by 
leaf characters. The latter species has a wide range of forms, and 
is but poorly circumscribed. It is quite possible that further 
knowledge of external characters may require these two species 
to be reduced to one. All the forms have well developed strength- 
ening cells. 
No thin-walled layer next the epidermis ; strengthening cells about 
ducts and in fibro-vascular region. 
= Leaves in fives: stomata deeply set. 
19. P. Coulteri Don. may be looked for in this group. — 
3. P. Torreyana Parry. Outline of section mostly triangu- 
lar: stomata numerous, 8-13 rows on each tace: 3-5 rows ‘ 
strengthening cells in cortical region: ducts mostly 3 (.040- 
-060 m.), sometimes with accessory internal ones: leaves 8-11 10- 
long. 
Coast of Southern California. 
= = Leaves in threes: stomata not deeply set. 
24. P. Jeffreyi Murray. Strengthening cells in 2 or 3 fet 
in cortical region; one complete row about ducts: ducts two ° 
more (.040-.060 mm.) : leaves 4-9 in, long. 
Eastern slope of the Sierras and ranging into Oregon. oe 
The leaf structure is much like that of P. ponderosa, to which species It 
_ often referred as a variety, but is very distinct in the absence of the sub-epi 
= dermal thin-walled layer. 
