ESSENTIAL FLORAL LEAVES. 105 
spond to the united edges, for at each of them is a ridge-like pla- 
centa bearing ovules. This kind of placentation is parietal (fig. 
48, E). The same term is applied where the united carpels are 
partly folded, so that the single loculus is divided into chambers 
at its margin. Thus in poppy there are a great many chambers, 
and the parietal placentas, which bear an immense number of 
minute ovules, project into the ovary. This can easily be verified 
in the dried poppy-heads sold by druggists (cf. fig. 48, F). 
Some ovaries are divided up by false or spurious dissepiments, 
so called because they are not partitions formed by union of 
adjacent carpels, but outgrowths from the wall of the ovary. In 
yellow corydal and Dielytra, both common garden plants, the 
synearpous pistil is formed by the union of two lateral carpels. 
The ovary is unilocular, and the ovules are borne on two parietal 
placentas, one anterior, the other posterior. Wallflower, stock, 
and shepherd’s purse, which are not very distantly related, pre- 
sent precisely the same arrangement, with this exception—the 
ovary is divided by a partition into right and left halves. This 
evidently does not correspond to the infolded edges of carpels, or 
the placentation would be axile. It is, however, parietal, and 
this fact, supported by comparison with the allied dielytra, &c., 
prove the partition to be an ingrowth. A study of the develop- 
ment confirms this view. Again, in dead nettle and sage the 
end of the style forks into anterior and posterior branches, which 
leads one to suspect the existence of two carpels, one anterior, 
the other posterior. The ovary, however, is fowr-lobed, and con- 
tains four loculi. This points to four carpels. The evidence 
given by the style is here really correct. Development shows 
that two is the actual number, but an ingrowth occurs from the 
dorsal margin of each carpel, dividing its cavity into two. Borage, 
forget-me-not, and their allies present the same feature, but are 
even more misleading, since in them the style is undivided, or at 
most slightly notched. 
The inferior syncarpous ovary (fig. 48, C), though its outer wall 
is partly formed by the cup-like receptacle, corresponds very 
closely in form and placentation with the supericr syncarpous 
one. Snowdrop and orchis will here serve, respectively, as 
examples of axile and parietal placentation. 
There are still other ways in which ovules may be arranged. 
Each one of the ten carpels of the flowering rush contains a large 
number of ovules which are scattered over the walls of the loculus, 
and not limited to the united margins. This is superficial pla- 
centation. It isa rare form, but also occurs in the syncarpous 
pistils of white and yellow waterlilies. 
Transverse and longitudinal sections of the ovary of a pink or 
