1886.] BOTANICAL GAZETTE. 305 
; jth San cells about ducts, but none in the cortical region, At- 
lantic species 
‘ P. resinosa Ait. Thin-walled cells small, ae eay | 
i tone, not half as large as the epidermal cells: leaves 5-6 i 
e 
Massachusetts to Minnesota. 
The ducts are mostly peripheral, as in the first section, though parenchy- 
ne ones are quite common. This species seems to form a sort of transition 
tween the two sections, which are apparently quite vanes separated here 
owing to the absence of about a dozen Old World species 
b. Str (ahaa cells in the cortical region, but none about ducts: Pacific 
coast species 
16. P. contorta Dougl. Thin-walled cells as in P. resinosa, 
and about half as large as the strengthening cells, which mostly 
orm but one continuous row interrupted only by stomata: ducts 
_ one or two, often ree — than in the next species(.050- 
-090mm.): leaves 1-1} in. long. 
All along the Pacific coast. 
hie old the leaf structure resembles that of P. Banksiana and P. inops* 
P. muricata Don. Thin-walled cells larger than in the 
Ente only a little smaller than the epidermal and larger 
than the aipeseihening cells : ducts 2-9, very small (.025-.040 mm.): 
leaves 4-6 in 
the coast Be ‘California. 
Th es has been confounded with forms of P. contorta, but they are 
well alitiaaictuhwe by the characters given above. 
— — Leaves in threes (sometimes fours or fives): ducts 2-10. 
Strengthening cells abundant in 
ay to ‘the duets ; ; rarely any about 
ducts 8-10, very 
18. P. Engelmanni Carr. 
cortical region, extending half w 
the duets ; abundant in fibro-vascular region: 
small (.020-, 030 mm.): leaves 13-15 in. long. 
Mountains of Mexico. 
Our description of this little known species is taken from specimens ob- 
. Eng elmann describes the single spec- 
developed strength 
epidermal cells. Parlatore considered this speci 
but its leaf structure is very distinct from what is 
phous species, 
2 
0 
found even in that polymor- 
