PLACENTATION,. 483 
that the carpels are invaginated within the expanded 
top of the flower-stalk and more or less adherent to it. 
Some of the gourds afford good illustrations of this, the 
upper part of the carpels in these fruits projecting 
beyond the axial portion. But this matter loses much 
of its importance if the morphological identity of axis 
and leaf-organ be conceded. The carpels in inferior 
ovaries seldom or never correspond to the lamina of the 
leaf, and between the vaginal portion of the carpellary 
leaf, and the axis who shall draw the distinction ? 
Placentation—Some botanists have considered the 
placentas to be portions of the carpel, and have com- 
pared the production of ovules on them to the forma- 
tion of buds on the leaf of Bryophyllum. Others 
have been led to see in each placenta, even when 
it is, to all outward appearance, a portion of the car- 
pellary leaf, a direct prolongation from the axis, ad- 
herent to the leaf. Teratology shows that ovules may 
be formed indifferently on leaf-organs or on stem-organs. 
Sutural, parietal, axile, free-central placentation, and, if 
there be more forms, all may be met with even in the 
same ovary (see pp. 96,508). Now, if there were such 
special tendencies in the axis, as contrasted with the 
leaf, to produce ovules, it 1s hardly likely that such 
anomalous arrangements as those just mentioned 
would be as frequent as they are. But as leaves 
produce other leaves, from their edges or their 
surfaces, and as they form buds in the same situations, 
just as axial organs do,’ there is surely little ground 
for considering the placentas, or ovuliferous portions 
of the plant, to be of necessity axial. Here again, 
much of the difficulty vanishes if the morphological 
1 It must, however, be borne in mind that no true leaf-organ has yet 
been seen with a bud at its exact apex (unless it be the nepaul barley), 
while in the case of an axial organ such a position of the bud is 
constant. The nearest approach is in the case of impari-pinnate leaves 
in which the terminal leaflet is jointed to the common rachis, and in 
the leaves of some Meliacew which continue to push farth new leaflets 
even after the leaf has attained maturity. 
