244 
W. T. Sax l on. 
be the superficial characters of the vegetative organs, including the 
shape and position of the leaves. These parts are by far the most 
important to the plant, physiologically, and for this reason are the 
most susceptible to adaptive changes. It may further be stated 
that (i) the superficial characters of the reproductive structures, and 
(ii) the internal anatomy of vegetative structures, especially the 
vascular system, are much more important, systematically, than the 
external features of non-reproductive parts. 
This principle was clearly recognized and applied, even beyond 
its legitimate limits, by Seward and Ford when they proposed 
to separate the Araucarians, on the basis of differences in both these 
classes of characters, from all other Coniferales, as a separate order, 
the Araucariales. Chief emphasis was laid on the characters of 
reproductive structures, but not so much on the gametophytes and 
embryo, which were then (and are still to a less extent) very 
imperfectly known, as on the external features and anatomy of 
reproductive organs. It may be worth while to point out that since 
the vascular bundles do not, except in rare cases, actually penetrate 
the reproductive structures, but only those parts of the plant 
(sporophylls) which bear such structures, the expression “ anatomy 
of reproductive organs ” refers to accessory organs, and not to the 
reproductive structures themselves; consequently such anatomical 
characters have a systematic value considerably less than characters 
concerned with the reproductive organs themselves, though some¬ 
what greater than the anatomical characters of purely vegetative 
parts. Thus, while it was very necessary that attention should be 
drawn to the fact that the two living genera of Araucarians, which 
undoubtedly form a small natural alliance, differ in many important 
respects from all other Conifers, perhaps even more widely than 
any two other alliances within the group differ from one another, 
yet it is probable that these differences are of quite the same order 
as those which may be used to separate other families within the 
group, e.g. Pinacese from Taxacese (in the sense in which those 
families are defined below). 
More important, however, than either of the two classes of 
characters just mentioned are those derived from the internal 
structure of the reproductive organs. This refers to the ovule, 
microsporangium, both gametophytes, and, at a later stage, the 
embryo. 
We may sub-divide such characters somewhat as follows:— 
1. Structure of young microsporangium. 
2 . Structure of ovule. 
