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earlier development of the ovules in their region than on 
parts of the placenta more remote, as might be expected 
where the function of seed-bearing has been transferred 
gradually from sporophylls to axial tissue, though this con- 
dition may be due to better nutrition. Too much emphasis 
can hardly be laid upon the peculiar character of the pla- 
centa in this family. We have noted the different forms 
which the placenta assumes and the varied structure of the 
ovary, and all the facts observed point to the placenta as a 
center of variation. It is here that we find evidence of the 
gradual assumption of the function of reproduction by tissues 
of an axial nature and a corresponding decrease in the extent 
to which foliar tissue is concerned in this work. This indi- 
cates a certain degree of plasticity in the axial tissue, which 
is further expressed in the multiplying of ovular series on the 
placental folds, to which attention has been called in the com- 
parison of forms like Melothria, Cucumis and Cucurbcta. 
It is apparent here that we have a condition of morphological 
independence in which new powers of variation are acquired, 
which have been utilized in the various modifications of pla- 
centa and ovary already pointed out. While it is true that 
the number of placental folds generally corresponds to the 
number of carpellary rudiments, this is not always so (Szcyos) ; 
and in those cases in which the number of placental ridges 
is usually three, four or five may sometimes be found (Cucur- 
bita Pepo); and where two is the rule three may occur, etc. 
In other words a condition of variability exists which is more 
or less restricted by hereditary tendencies (Ganong”). 
The more important features of the ovule and embryo-sac 
of the various species examined have been described. A 
comparison of these facts shows a considerable degree of uni- 
formity in the development of these structures between the 
most widely varying members of the family. The ovule in 
all cases is anatropous and the relative importance, in point 
of size, of the nucellus and the integuments is quite constant 
in all the species investigated. The ovules of the Cucur- 
bitaceae differ from those of most other Sympetalae in some 
