ESSENTIAL FLORAL LEAVES. - IO7 
Structure.—The pistil is made up of the usual three systems 
of tissue, but only a few of the more important details can be 
given here. Cross-sections through one of the ovaries of larkspur 
or columbine will show a well-marked notch on the ventral side, 
a gaan to the ventral suture. A layer of epidermis is 
present on the outside, which can be traced right through the 
wall where the notch occurs, after which it becomes continuous 
with a layer of epidermis lining the loculus. The carpel being a 
folded leaf, we might have expected this. The outer and inner 
epidermis correspond, in fact, to the lower and upper layers of 
epidermis in a foliage leaf (cf. p. 64), and in a very young ovary 
of larkspur the margins of the carpel will be found in contact, 
but not united. It is also interesting to note that the inner epi- 
dermis possesses stomata as well as the outer, though they appear 
to be useless in such a position.. Between the epidermic layers 
comes the parenchymatous ground-tissue traversed by numerous 
vascular bundles. Each margin of the carpel is swollen slightly 
at the ventral structure, so as to form a placenta, upon which 
a row of ovules is borne, as can be seen in a longitudinal 
section. 
Cross-sections through a syncarpous ovary, such as that of lily, 
hyacinth, or violet, do not show sharp boundaries between the 
constituent carpels (cf. fig. 50). The outside is covered by a 
continuous layer of epidermis, which does not dip inwards where 
the carpels unite. Hach loculus is lined by its own separate 
layer of epidermis. 
The style is sometimes traversed by a pollen canal, as in lily 
and hyacinth. ‘This canal may open to the exterior in the centre 
of the stigma, as in pansy (fig. 50). More frequently the centre 
of the style is occupied by a very delicate, loose, conducting tissue, 
as, €.g., in fuchsia and evening primrose. 
The stigma is frequently provided with delicate hairs, and its 
cells generally form minute projections or papille at the surface. 
‘They also secrete a sticky fluid when the stigma is mature. 
An ovule (figs. 48 and 49) is a minute ovoid body, in which 
there is an attached fase or chalaza and a free apex. The base 
is In most cases fixed to the placenta by a slender stalk, the 
Funicle, which is traversed by a vascular bundle. The ovule is 
covered by either one or two skins or integuments, within which 
is a central mass of cells, the nucellus. ‘The integuments do not 
cover the extreme apex of the ovule, where a short canal, the 
micropyle, is left, which leads down to the nucellus. One integu- 
ment only is present in gymnosperms and most gamopetalous 
dicotyledons, while there are two in nearly all monocotyledons 
and many dicotyledons. In the latter case the inner coat, being 
