48
DAVID D. KECK
if it is useful. Sometimes the most practical classification is not the most
natural. The frequent employment of artificial keys in groups that have
been amply studied is one result of this fact.
The principal structure of our classification system has already been
built following principles laid down from experience with the primary
tools of comparative morphology and distribution. The refinements
added to the system through the use of secondary tools of various sorts
will accrue slowly because the methods are laborious, so they will of
necessity be of minor import to the system as a whole for a considerable
time to come. Biologists subscribing to this view realize that an uneven
classification will result, reflecting the present state of our knowledge, so
that for example the classification of one genus may rapidly become
clarified and refined as intensive experimental work produces the necessary data, while its sister genera may remain imperfectly known. But
unevenness of treatment has always been the accepted fact in taxonomy,
and impulsion to correct the situation is one factor lying behind the constant stream of revisions and monographs that appear.
Students concerned with the classification of the higher plants find
much primary work yet to be done in many parts of the world, particularly in the tropics and subtropics. In most of the temperate and
even the arctic regions, possibly excluding those in Asia, the floras are
becoming fairly well known, and refinements in the classification of
group after group of these plants have appeared or are being initiated.
The need is for botanists to continue toward their ultimate goal along
all these fronts, but the tools that each will employ will depend in good
part upon the state of our knowledge of the plants before him. Obviously, one cannot yet find in the literature or even obtain for himself
cytogenetic data, for instance, on the constituents of the floras of such
areas as New Guinea, Equatorial Africa, or the Amazon Basin. He can
systematize these constituents satisfactorily, however, by classifying them
carefully with the conventional methods. The worker dealing with the
temperate zone floras of Europe or North America, on the other hand,
often has available or can obtain a variety of facts. He may be called
upon to weigh the possibility that the taxa before him have arisen in
various ways (through mutation, chromosomal changes including polyploidy and recombination, hybridization, selection, formation of genetic
or structural barriers, environmental change, migration, etc.); that the
new evolutionary products, if taxa, must perpetuate themselves; and that
they must be in adjustment with their environment. From the evolutionary point of view it is often important that a new taxon is able to make
adjustments to conditions in more than a single way. But all these con-
DAVID D. KECK
if it is useful. Sometimes the most practical classification is not the most
natural. The frequent employment of artificial keys in groups that have
been amply studied is one result of this fact.
The principal structure of our classification system has already been
built following principles laid down from experience with the primary
tools of comparative morphology and distribution. The refinements
added to the system through the use of secondary tools of various sorts
will accrue slowly because the methods are laborious, so they will of
necessity be of minor import to the system as a whole for a considerable
time to come. Biologists subscribing to this view realize that an uneven
classification will result, reflecting the present state of our knowledge, so
that for example the classification of one genus may rapidly become
clarified and refined as intensive experimental work produces the necessary data, while its sister genera may remain imperfectly known. But
unevenness of treatment has always been the accepted fact in taxonomy,
and impulsion to correct the situation is one factor lying behind the constant stream of revisions and monographs that appear.
Students concerned with the classification of the higher plants find
much primary work yet to be done in many parts of the world, particularly in the tropics and subtropics. In most of the temperate and
even the arctic regions, possibly excluding those in Asia, the floras are
becoming fairly well known, and refinements in the classification of
group after group of these plants have appeared or are being initiated.
The need is for botanists to continue toward their ultimate goal along
all these fronts, but the tools that each will employ will depend in good
part upon the state of our knowledge of the plants before him. Obviously, one cannot yet find in the literature or even obtain for himself
cytogenetic data, for instance, on the constituents of the floras of such
areas as New Guinea, Equatorial Africa, or the Amazon Basin. He can
systematize these constituents satisfactorily, however, by classifying them
carefully with the conventional methods. The worker dealing with the
temperate zone floras of Europe or North America, on the other hand,
often has available or can obtain a variety of facts. He may be called
upon to weigh the possibility that the taxa before him have arisen in
various ways (through mutation, chromosomal changes including polyploidy and recombination, hybridization, selection, formation of genetic
or structural barriers, environmental change, migration, etc.); that the
new evolutionary products, if taxa, must perpetuate themselves; and that
they must be in adjustment with their environment. From the evolutionary point of view it is often important that a new taxon is able to make
adjustments to conditions in more than a single way. But all these con-