1886. | BOTANICAL GAZETTE. 307 
25. P. Sabiniana Dougl. Strengthening cells in bundles in 
cortical region, and usually about ducts; which are mostly two 
(.020-.050 mm.): the cells of the bundle-sheath are often thin- 
walled, and the species may be looked for under the next group: 
leaves 8-12 in. long; the section considerably smaller than in P. 
Coulteri, with which it may be confused, 
Mountains of California. 
+ +  Bundle-sheath thin-walled: a thin-walled layer next the epi- 
dermis. : 
++ Strengthening cells in fibro-vascular region; few, if any, about ducts, 
= Leaves in threes. 
26. P. Teda L. Strengthening cells in the angles much larger 
than epidermal cells, in the rest of the cortical region only about 
half as large; also on dorsal side in fibro-vascular region: ducts 
quite large for the section (.037-.075 mm): leaves 5-6 in long. 
Delaware to Florida and,westward to Arkansas. 
27. P.serotina Michx. Strengthening cells equalling the ep- 
idermal cells, or smaller, numerous in the angles, elsewhere in the 
cortical region in bundles or single layers; generally absent from 
the ducts; in the fibro-vascular region on either or both sides of 
the fibro-vascular bundles: cells of the thin-walled layer quite 
small: ducts mostly 5-7, often half of them internal (.025-.050 
mm.): leaves 6-8 in. long. 
From N. Carolina to Florida. 
28. P. rigida Miller. Like the last, but strengthening cells 
tical region, in two or three rows, about 
not so numerous in the cor 
angles: ducts 3-7: 
the size of the epidermal cells, or larger in the 
leaves 3-5 in. long. 
From New Brunswick to Kentucky. 
29. P. insignis Dougl. Epidermal cells forming an arch next 
the stomata, making an oval cavity which opens below: strength- 
ening cells (as well as thin-walled layer) mostly larger than epi- 
dermal cells, in one or two rows in the cortical region; sometimes 
found in the fibro-vascular region: leaves 4-6 in. long 
Coast of California. 
19. P. Coulteri Don., 
31. P. tubereulata Go 
= = Leaves in pairs. 
30. P. pungens Michx. 
and a 
rdon, may be looked for in this group. 
Thin-walled cells quite small: 
