OF THE GENUS PINUS. 569 
The series in which the bud-scales are more or less persistent, 
tightly imbricated and subcoriaceous in texture (at least at the 
base), includes two principal groups, the one in which the leaves 
vary from 3 to 5 in a tult and are 3-sided (Pl. 21. fig. 6), and the 
other that in which the leaves are in pairs, semiterete, grooved 
or flattish on the upper surface, and, when cut across, presenting 
the outline of a section of a boat (Pl. 20. fig. 1). 
The group in which the leaves are 3-sided admits of division 
into the sections Indice (Engelmann), Ponderose (Engelmann), 
Filifolie (corresponding nearly to Engelmann’s Pseudostrobi), 
and Cubenses (Engelmann’s Australes). 
The 2-leaved group is very distinct, but allows of subdivision 
into two sections—the Silvestres (Engelmann in part) and 
Pinaster, according as the resin-canals are marginal, as in 
P. silvestris and its allies, or median as in P. Laricio, ete. 
The sections here proposed correspond in many particulars 
with those set forth by Engelmann and with some of the 
subdivisions adopted by the older writes, but they are grouped 
differently, and their constituent species are not always the 
same. 
Further remarks on the ten sections of the genus here 
proposed will be included in the notes relating to individual 
species. 
PINUS. 
Division I. TENUISQUAM, 
Cones near the ends of the shoots; cone-scales leathery or 
slightly woody, not specially thickened near the apex or on 
either side of the terminal umbo. Bud-scales thin, membranous. 
Leaf-sheaths mostly deciduous, often leaving a short, persistent, 
frill-like ring at the base. Leaves 5, 3-sided, meristele circular 
in section. Fibro-vascular bundle simple. 
Section 1. Srrosus. 
Resin-canals marginal, rarely median (as sometimes in Lam- 
bertiana) ; seeds winged .....-.-++++eeer eee? Spp. 1-10. 
Section 2, CeMBRA. 
Resin-canals median; seeds wingless or nearly so. Spp. 11-13. 
