1892. ] Development of the Flower. 353 
Development of the flower and embryo-sac in Aster and 
Solidago. 
G. W. MARTIN. 
(WITH PLATES XIX AND XxX.) 
Before entering directly upon the subject it may be well to 
recount the primitive conditions of the leaf-shoot and its 
growing point as found in Composite. The point of growth 
of the shoot-axis becomes very much retarded, and as a re- 
sult, the growing-point is transformed into a broad, somewhat 
elevated disc, on which are to appear flowering capitula with 
centripetal inflorescence (fig. 1). The first structure indicat- 
ing an individual, embryonic flower on the receptacle is a 
hemispherical outgrowth almost perfect in outline, and becom- 
ing obconical as growth takes place (figs. 2a and 3a).! This 
embryonic tissue, standing on a lateral axis, constitutes the 
foundation from which arises a differentiation of tissue into 
special organs (fig. 4). Thus far the path of embryonic devel- 
opment remains the same for all organs, even those of the 
most various kinds. From this condition of things on a new 
the apex of the broad flower-axis ceases 
J 
Parts till liberated a deep, central depression is forming, 
when ultimately the ovule-bearing portion is place 
the rest of the flower-parts (figs. 6-10). Thus we have an 
€pigynous flower with an inferior ovary- 
are some who would substitute the word hypogy 
epigynous, basing their argument on the theory that all the 
moral Organs in their initial state are coalesced in the annular 
‘Just here may be stated that this rudimentary, sessile floret is the firstindi- 
eh subdivision. 
uctural Botany, p. 183. 
