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A. B. STOUT 
standing of morphogenetic differentiation involved in sexuality, but of 
which we have at the present time only a superficial knowledge. 
When does physiological incompatibility begin to develop? Is it 
a steady and progressive development through the whole diploid 
association of the two parental cell elements involved, or is it achieved 
suddenly at some particular point in ontogeny? Also, when does the 
sexual condition as distinct from the asexual condition actually arise? 
Does incompatibility arise because of sex? Are the two the same? 
It would seem most definitely that they are not and that incompati- 
bilities are not merely due to sexuality. But even if independent, 
where incompatibilities do arise, where, how, and to what extent are 
they correlated with sex and is the development of the two ever 
parallel? To what extent are the physiological interrelations of 
sexuality and incompatibility dependent on such mechanical or 
chemical interactions as are involved in reduction and sporogenesis? 
Are the differences of intra-varietal physiological compatibility 
and incompatibility (both self and cross) indicative of differences in 
sexuality as such? Are some of the organs of either sex (microgameto- 
phytes and macrogametophytes with their respective gametes) 
sometimes more sexual or of greater sex vigor than are others? 
To what degree are the incompatibilities, and compatibilities as 
well, determined by nutritive relations that are to be considered as 
vegetative functions? Is sexuality in its origin and in its phenomena 
of cell fusions, as some have held, to be considered in reality as a 
phase of vegetative function? To what extent are the sexual incom- 
patibilities related to phenomena of serum incompatibilities and to 
immunity and what are the fundamental reactions involved in the 
development and operation of these? 
These are among the fundamental questions that naturally arise 
in connection with such sporadic behavior of functional vsex vigor as is 
seen in chicory in which self-fertile plants of varying degrees of fertility 
arise among a progeny even after three generations of parentage 
known to be self-sterile. 
New York Botanical Garden 
BIBLIOGRAPHY 
Compton, R. H. 1912. Preliminary Note on the Inheritance of Sterility in Reseda 
odorata. Proc. Cambridge Phil. Soc. 17: Pt. i. 
1913. Phenomena and Problems of Self-sterility. New Phytologist 7: 197-206. 
