lution attained by each
group, but not all the species of a group conform exactly with its
definition. In each group are species with a characteristic of another
group. Among the Lariciones are a few species with both symmetrical
and oblique cones, and two with persistent cones. Similar exceptions
occur among the Australes. Among the Insignes are a few species with
symmetrical cones, and two with cones that are rarely, if ever,
serotinous.

There is, however, no difficulty in fixing the systematic position of
these exceptional species through other characters which show their
true affinity. They are placed with the species which they most
resemble. Their exceptional characters are merely the evidence of the
evolution that pervades and unites the groups. Therefore the
definition of a group is not necessarily the exact definition of its
species, and a species is placed in a group because all its
characters, specific and evolutional, show a closer affinity with that
group than with the species of any other.

=X. LARICIONES=

Pits of the ray-cells large. Cells of the leaf-hypoderm uniform.
Spring-shoots uninodal. Cones dehiscent at maturity.

This group represents the first stage in the evolution of the Hard
Pines. All the species, like the Soft Pines, are uninodal and the
cones are dehiscent at maturity, but the trend toward the serotinous
species is shown in the occasional appearance of the oblique cone as a
varietal form of a few species, and in the persistent cone of the last
two species of this group.

All the species of this group are of the Old World except P. resinosa
and P. tropicalis. These two are the only American Pines combining
large pits with dentate tracheids, and are the only American Hard
Pines with external resin-ducts of the leaf.

Cones deciduous at maturity.
Cones ovate or ovate-conic.
Conelet with tuberculate or entire scales.
Resin-ducts external and medial 25. resinosa
Resin-ducts septal and external 26. tropicalis
Conelet with mucronate scales.
Resin-ducts mostly external.
Conelet pedunculate, erect.
Cone nut-brown 27. Massoniana
Cone dull tawny yellow 28. densiflora
Conelet pedunculate, reflexed 29. sylvestris
Conelet subsessile, erect 30. mo