130 BOTANICAL GAZETTE [FEBRUARY 
morphological and physiological differentiations constituting sexu- 
ality is initiated in the morphogenesis of flowers. The cells of 
pistils and stamens are not only alike in their preformed genetic 
composition, but they are identical in this particular with the cells 
that entered into the preceding vegetative structures. CORRENS 
(2) has noted that the regeneration from sister cells of the egg and 
sperm (the archegonial and antheridial cells) in certain monoecious 
mosses shows that, at least in hermaphrodites and monoecious 
plants, maleness and femaleness are carried equally by both male 
and female gametes. The male gametophytes and their most 
highly specialized male cells are male only because of a temporary 
suppression of femaleness. Likewise the femaleness of egg cells is a 
temporary and one-sided expression of cells carrying both sex 
potencies. The various expressions of maleness and femaleness 
even in the sex generation, at least in hermaphrodite plants, 
according to CoRRENS, are ‘‘phenotypic”’ or biogenetic expressions 
independent of any qualitative differentiation in the component 
units of the germ plasm. The expressions of the so-called factors 
for sex or the so-called inhibitors of one or the other sex are hence 
independent of corresponding differentiations in germ plasm which 
may have arisen during sporogenesis. The expression of sex, 
therefore, is on the same basis as are the somatic differentiations 
that arise among the various parts of the individual. It hence 
becomes a most fundamental biological problem to consider and 
to determine as far as possible what conditions determine these 
differences in the level of the so-called ‘‘physiological gradient.” 
Maturity, with its transition from the vegetative to the repro- 
ductive phase, whether giving homologous or antithetic alternation 
or a continuation of either, occurs in cycle after cycle with remark- 
able uniformity. This emphasizes the phylogenetic or hereditary 
aspect of particular phases of the development. One may assume 
a “gene” ora “factor” for maturity, and assume that it is gradually 
awakened from a dormant condition to the exercise of its influence 
at a particular time and in a particular group of cells. One may 
further assume that the loss of such a gene would throw a line of 
progeny into a condition of perpetual immaturity, so that flowers 
or other reproductive organs could never be formed. The evidence 
