CHAP. I. 
REGULAR METAMORPHOSIS. 
537 
We now come to the consideration of a fourth series of the 
fructification, the disk ; this is so frequently absent, and is 
of so obscure a nature, that few morphorlogists take it into 
their consideration. It is, however, necessary to understand 
it, if possible, especially as, when present, it occasionally pre- 
sents itself under very singular and various forms. In many 
plants it consists of a mere annular fleshy ring, encompassing 
the base of the ovary ; in others it forms a sort of cup, in 
which the ovaries are inclosed, as in certain Paeonies ; and it 
very frequently makes its appearance as hypogynous glands or 
scales : it is almost always between the stamens and pistil. 
That it is not an organ of a distinct nature may, I think, 
be safely inferred from its having no existence in a large num- 
ber of flowers : but if it is not an organ of itself, it must be 
a modification of something else ; and in that view, from its 
situation, it would be referable either to the stamens or pistil. 
It has so little connection with the lattei', from which it always 
separates at maturity, that it can scarcely be referred to it. 
With the stamens it has, perhaps, a stronger relation : it con- 
sists of the same cellular substance as the connective of the an- 
thers ; is very often of the same colour ; whenever it separates 
into what are called hypogynous glands or scales, these always 
alternate with the innermost series of stamens. In the Pseony 
the disk may, in some measure, be compared to the inner row 
of scales which exists between the stamens and pistil of the 
nearly related genus Aquilegia. Dunal has noticed half the 
disk of a Cistus bearing stamens ; and a variety of instances 
may be adduced of an insensible gradation from the stamens 
to the most rudimentary state of this organ. 
The fifth and last series of fructification is the pistil. Let 
us first consider this organ in its simple state, and then advert 
to it in a state of composition. The simple pistil, that of the 
pea for instance, consists of an ovary, bearing its ovules on 
one side in two parallel contiguous rows, and at its upper ex- 
tremity tapering into a style which terminates in a stigma. 
If this organ be further examined, it will be found that there 
is a suture running down each edge from the style to the 
base ; it will be also seen that the ovules are attached to one 
of these sutures, and that the style is an elongation of the 
