50
DAVID D. KECK
individual, but then he may turn to the breeding population, or to the
hierarchy made up of the biotype, ecotype, ecospecies, cenospecies, and
comparium. When considering evolutionary units the cytologist thinks
first in terms of the gene, then the chromosome segment, next the
chromosome itself, and finally the genome or entire haploid set of
chromosomes. These various terms and concepts are necessary to describe precisely the dynamics of the speciation process as seen from different points of view.
The taxonomist should be familiar with all these terms and able to
apply them, but fortunately he has been able to avoid recasting his classical nomenclature completely even when faced with the new data. The
question as to whether he could do so has been of concern, as a stable
botanical nomenclature is the desire of all botanists (Rickett and Camp,
1948; Turrill, 1950; Camp, 1951). The new kinds of data that have been
developed particularly by the experimentalist, and which show how all
life is organized into dynamic groups of various sizes and degrees of
complexity, with hereditary distinctions as shown by physiological reactions to the environment, morphological variations, differences in
chromosome number and morphology, and so on—these have been of
the greatest use in realigning his own classifications and gaining that
greater objectivity which the actual tests of relationship afford, but at
the same time the taxonomist has preserved the genus-species nomenclature familiar to almost every layman. After the experimentalist has
touched them, some of our species may not be just what they were before
(the classical taxonomist has been continually sharpening their definitions
anyway, irrespective of the newer approaches), but at least they are
still species. In their new circumscription they are less debatable than
they were before.
A concept of species essentially comparable to the Linnean one is
still the basic unit of classification under either system. The classical
taxonomist and the experimental taxonomist find that their individual
standards bring them into essential agreement here (Gleason, 1952).
The genus, also, is a unit that is not in danger of being overthrown by
all the data that can be brought together through cytogenetic or biosystematic activity. These concepts are subject to individual modification
as the new evidence clarifies the picture for us, and thus the ultimate
classification will be an improvement over the present one. But this is
a matter of detail rather than of fundamental principle. Some of the
units of the biosystematist, such as the ecotype, for example, may or
may not have a direct counterpart in the classical systematic system, depending upon the presence or absence of adequate morphological
DAVID D. KECK
individual, but then he may turn to the breeding population, or to the
hierarchy made up of the biotype, ecotype, ecospecies, cenospecies, and
comparium. When considering evolutionary units the cytologist thinks
first in terms of the gene, then the chromosome segment, next the
chromosome itself, and finally the genome or entire haploid set of
chromosomes. These various terms and concepts are necessary to describe precisely the dynamics of the speciation process as seen from different points of view.
The taxonomist should be familiar with all these terms and able to
apply them, but fortunately he has been able to avoid recasting his classical nomenclature completely even when faced with the new data. The
question as to whether he could do so has been of concern, as a stable
botanical nomenclature is the desire of all botanists (Rickett and Camp,
1948; Turrill, 1950; Camp, 1951). The new kinds of data that have been
developed particularly by the experimentalist, and which show how all
life is organized into dynamic groups of various sizes and degrees of
complexity, with hereditary distinctions as shown by physiological reactions to the environment, morphological variations, differences in
chromosome number and morphology, and so on—these have been of
the greatest use in realigning his own classifications and gaining that
greater objectivity which the actual tests of relationship afford, but at
the same time the taxonomist has preserved the genus-species nomenclature familiar to almost every layman. After the experimentalist has
touched them, some of our species may not be just what they were before
(the classical taxonomist has been continually sharpening their definitions
anyway, irrespective of the newer approaches), but at least they are
still species. In their new circumscription they are less debatable than
they were before.
A concept of species essentially comparable to the Linnean one is
still the basic unit of classification under either system. The classical
taxonomist and the experimental taxonomist find that their individual
standards bring them into essential agreement here (Gleason, 1952).
The genus, also, is a unit that is not in danger of being overthrown by
all the data that can be brought together through cytogenetic or biosystematic activity. These concepts are subject to individual modification
as the new evidence clarifies the picture for us, and thus the ultimate
classification will be an improvement over the present one. But this is
a matter of detail rather than of fundamental principle. Some of the
units of the biosystematist, such as the ecotype, for example, may or
may not have a direct counterpart in the classical systematic system, depending upon the presence or absence of adequate morphological