FLOWER AND FRUIT 159 
placentation is axile and the ovules are, in the lily, 
situated on three axile placentae. Externally, the lines 
of union as well as the midribs of the earpellary leaves 
may easily be distinguished. 
Free central is a further development from axile 
placentation. First the leaves bend in, and, as before, 
mass the ovules on placentz forming the central axis. 
The ovary has now as many chambers as there were 
earpellary leaves, each chamber being divided from 
the others by the wall or septum formed from the 
infolded parts of two adjacent leaves. In some 
flowers, as for instance the primrose, these septa 
disappear and the ovules are left attached to an axis 
which stands free in the centre: hence the term free 
central. In the carrot, parsnip, and other members of 
that family the ovules are suspended, 7.e., hang, one 
from the roof of each chamber of the ovary. Where 
the carpels are united, as in the lily and the primrose, 
the gynecium is said to be syncarpous, but where 
they are free, as in the buttercup, it is apocarpous. 
The style serves the purpose of lifting the stigma 
to the position most convenient for reeeiving pollen. 
It is generally straight, but in the pea and violet it is 
bent almost at right angles. 
A stigma, which, owing to the absence of a style, 
lies immediately on top of the ovary, as is the case 
with the tulip, is said to be sessile. The stigma is the 
receptive part of the pistil. It receives and holds the 
pollen grains, and provides them with a sugary 
nutritive material that enables them to germinate. 
If the stigmas be removed from a number of flower- 
buds the seeds will not develop. The pollen grain 
serminating on a stigma sends down to the ovule a 
tube, which enters the micropyle and discharges a 
dense piece of protoplasm ealled a nucleus. This 
nucleus fuses with a similar but larger structure called 
the egg cell, which is situated in the ovule itself. It 
