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 " or a "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 



