42
JOHN G. TORREY
meristematic masses which become the centers for organized primordia,
such as for root or shoot apical meristems, or for discrete structures,
such as whole embryos. In this view, meristemoids may be determined
at different stages in their course of development—some very early—
perhaps by an unequal division, and differentiated directly into a particular cell type. Others remain undetermined until quite late and retain
the form of a meristematic mass of cells capable of further divisions,
but require specific directive stimuli to lead to organized root or shoot
meristems or, in certain cases, to typical bipolar embryos with primordia
of both shoot and root meristems. One of the implications of this view is
that every living plant cell capable of being stimulated to divide is a
meristemoid, potentially able and genetically capable of differentiating
or developing into any cell type or of forming any one of a variety of
multicellular structures. Such a cell goes in any one particular direction
in response to the total influences, chemical and physical, impressed on it
from its environment, which interact with the intrinsic genetic control
mechanisms.
It is useful to examine the evidence concerning the control of cell differentiation, organ initiation, and embryo development in organ and
tissue culture from this point of view and to see to what extent the
generalization holds that these seem to be essentially similar phenomena involving the behavior of meristemoids. It is important to see
further to what extent one can define the conditions which determine the
direction which differentiation takes in each case. In such an analysis,
it is also useful to compare examples taken from similar phenomena in
intact or more or less integrated systems.
To examine all the evidence or even a large part of it is considerably
beyond the scope of this essay. Only isolated examples will be cited as
illustrating particular phenomena; thus many well-described and documented cases in the literature will be omitted, and no attempt will be
made to "cover" the literature. A number of books and reviews which
bear on the subject are available, and the reader is referred to them for
more detailed considerations, for further examples, and for discussions of
related phenomena. Reference should be made to an earlier volume of this
series for the review by Steward and Mohan Ram (1961). On anatomical
and morphological aspects, reference should be made to Priestley and
Swingle (1929), Bünning (1948), and Sinnott (1960). Several monographs on plant tissue culture have become available; Gautheret's "La
culture des tissus végétaux" (1959) is perhaps the most complete review.
Other volumes devoted to plant tissue culture research include that of
White (1943) and Butenko (1964). Lacking any unified publication outlet, plant tissue culture research workers have published in separate vol-
JOHN G. TORREY
meristematic masses which become the centers for organized primordia,
such as for root or shoot apical meristems, or for discrete structures,
such as whole embryos. In this view, meristemoids may be determined
at different stages in their course of development—some very early—
perhaps by an unequal division, and differentiated directly into a particular cell type. Others remain undetermined until quite late and retain
the form of a meristematic mass of cells capable of further divisions,
but require specific directive stimuli to lead to organized root or shoot
meristems or, in certain cases, to typical bipolar embryos with primordia
of both shoot and root meristems. One of the implications of this view is
that every living plant cell capable of being stimulated to divide is a
meristemoid, potentially able and genetically capable of differentiating
or developing into any cell type or of forming any one of a variety of
multicellular structures. Such a cell goes in any one particular direction
in response to the total influences, chemical and physical, impressed on it
from its environment, which interact with the intrinsic genetic control
mechanisms.
It is useful to examine the evidence concerning the control of cell differentiation, organ initiation, and embryo development in organ and
tissue culture from this point of view and to see to what extent the
generalization holds that these seem to be essentially similar phenomena involving the behavior of meristemoids. It is important to see
further to what extent one can define the conditions which determine the
direction which differentiation takes in each case. In such an analysis,
it is also useful to compare examples taken from similar phenomena in
intact or more or less integrated systems.
To examine all the evidence or even a large part of it is considerably
beyond the scope of this essay. Only isolated examples will be cited as
illustrating particular phenomena; thus many well-described and documented cases in the literature will be omitted, and no attempt will be
made to "cover" the literature. A number of books and reviews which
bear on the subject are available, and the reader is referred to them for
more detailed considerations, for further examples, and for discussions of
related phenomena. Reference should be made to an earlier volume of this
series for the review by Steward and Mohan Ram (1961). On anatomical
and morphological aspects, reference should be made to Priestley and
Swingle (1929), Bünning (1948), and Sinnott (1960). Several monographs on plant tissue culture have become available; Gautheret's "La
culture des tissus végétaux" (1959) is perhaps the most complete review.
Other volumes devoted to plant tissue culture research include that of
White (1943) and Butenko (1964). Lacking any unified publication outlet, plant tissue culture research workers have published in separate vol-