THE MORPHOLOGY OF THE РБІМІЛ,АСЕ Ж, 295 
So far, then, as the nature of the placenta is concerned, we have two theories : according | 
to the one it is essentially axial; according to the other it is foliar. Organogenetie 
evidence is strongly in favour of the axial view, though it is quite clear that, had it been 
practieable to observe the mode of development of the monstrous Primroses above 
described, the foliar nature of their placenta would have been proportionally as obvious 
as in the adult state. 
The evidence derived from minute anatomy is conflicting; and it is doubtful whether 
so much importanee should be attached to the position of the vascular bundles and of 
their constituent elements as Van Tieghem is disposed to attribute to them. 
Comparative morphology is entirely in favour of the axial view ; there is not, so far as 
lam aware, a single genus of Primulacez or of Мутвіпасеге where, under normal cir- 
cumstanees, the placenta is any thing else but ** free central." 
Teratology, as we have seen, affords support to either view, and lands us in this 
dilemma. Either we must say that any or all forms of placentation, foliar and axial, 
may occur in Primulaceze—a conclusion to which morphologists would certainly demur, 
except as a monstrous condition; or we must admit that the evidence afforded by 
teratology is utterly worthless in deciding such cases, and that the appearances in question 
are, in fact, simply accidental and abnormal. То this latter conclusion equally strong 
objeetion may be taken. Extraordinary as these appearances sometimes are, they may 
generally be easily referred to ordinary morphological laws. If this be admitted, as it 
must surely be by any one who has paid any attention to the subject, then we are sent 
back to the morphological dilemma above mentioned. 
As a provisional means of dealing with it, it may be suggested, as an hypothesis, 
that the stock from which Primulacee descended had parietal placentation, but that 
in course of time the placentas have become detached from the walls of the ovary, and 
fused together to form the free central placenta. Looked at in the light of this hypo- 
thesis, the monstrous flowers above alluded to, showing every gradation between саг- 
pellary and axial placentation, are mere reversions to an ancestral form. 
For this hypothesis it must be admitted no evidence can be adduced beyond that of 
the monstrosities in question and the occasional presence of a little filamentous process 
(the filet of St.-Hilaire) connecting the placenta with the apex of the ovarian cavity—a 
process the existence of which is doubted by Duchartre, but which is nevertheless осса- 
sionally to be seen on making sections of young Primulaceous ovaries, and which is, on 
this hypothesis, to be explained as a rudiment of the process of chorisis, by which the 
former generations of Primroses changed their parietal for a free central placenta. 
OvuLEs.—From the ordinary appearance of the placenta in Primulacez, and the 
position of the ovules upon it, it might well be supposed that the ovules or, rather, their 
outer coats were independent of the carpels, and direct outgrowths from an axial pla- 
centa, each ovule being the representative of a distinct leaf or phyllome. The cases 
recorded by Unger, Alphonse deCandolle, Brongniart, Marchand, Cramer, and others *, 
* Vegetable Teratology, p. 263. 
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