ted oblique cone
with an elaborate form of winged seed and an intermittent dissemination,
appears among the species in various degrees of development as follows--

The seed

1. wingless.
2. with a rudimentary wing.
3. with an effective adnate wing.
4. with an ineffective articulate wing.
5. with an effective articulate wing.
6. with an articulate wing, thickened at the base of the blade.

The cone

1. indehiscent.
2. dehiscent and deciduous.
3. dehiscent and persistent.
4. persistent and serotinous.

and as to its form

5. symmetrical.
6. subsymmetrical.
7. oblique.

These different forms of the seed and, to some extent, of the cone, are
available for segregating the species into groups of closely related
members; while the gradual progression of the fruit, from a primitive to
a highly specialized form of cone and method of dissemination, points to
a veritable taxonomic evolution which is here utilized as the
fundamental motive of the systematic classification of the species.

SPECIFIC CHARACTERS

All aspects of vegetative and reproductive organs may contribute toward
a determination of species, but the importance of each character is
often relative, being conclusive with one group of species, useless with
another. Characters considered by earlier authors to be invariable with
species, such as the dimensions of leaf or cone, the number of leaves in
the fascicle, the position of the resin-ducts, the presence of pruinose
branchlets, etc., prove to be inconstant in some species. In fact, as
the botanical horizon enlarges, the varietal limits of the species
broaden and many restrictions imposed by earlier systems are gradually
disappearing.

Variation is the preliminary step toward the creation of species, which
come into being with the elimination of intermediate forms. Variation in
a species may be the result of its participation in the evolutionary
processes culminating in the serotinous Pines, or it may result from the
ability of the species to adapt itself to various environments by
sympathetic modifications of growth, or it may arise from some
peculiarity of the individual tree.

Evolutionary variation is associated with the gradual appearance of the
persistent, the oblique and the serotinous cone, and of the multinodal
spring-shoot. For these conditions appear in less or greater prevalence
a