22 OUTLINE OF STRUCTURAL BOTANY 
and brightly colored parts. It may indeed consist of a single 
stamen lodged against the stem in the axil of a leaf or of a pistil 
unprotected by any envelope. In such a case the grace and brilli- 
ancy of the flower as it is usually thought of, is absent but at 
least one of the two essential elements necessary to the perpetuation 
of the species is present and in the view of the botanist this con- 
stitutes a flower. 
A flower, then, consists of a more or less complicated apparatus 
essential to the inception and perfection of the seed. 
Two elements are absolutely essential to this process of repro- 
duction of what are known as the higher plants, flowering plants. 
One is found in the pistil, at the base of which, or constituting 
the whole of which, is the ovary in which is found the ovule or 
ovules or, eventually, the developed seed. 
The other element is seen in the stamen which furnishes the 
pollen which must be applied to the pistil in order to fertilize it 
and without which the ovules can not develop into seeds. 
The transference of this pollen from the stamen to the pistil 
may be affected by the wind, by water, by insects or by other 
agencies. 
Hither of these elements, as we have seen, may be found alone, 
unaccompanied by the other element or by the conspicuous parts 
usually regarded as the flower. The flexible “ pussy” of a willow 
consists of a great number of single flowers, each consisting of a 
pair of stamens at the base of which there is a single colorless 
Fie. 22 Fic, 23 Fig. 24 Fig. 25 
bract, or if the catkin is made up of ‘pistillate flowers each flower 
consists of a single pistil with its bract (Figs. 22 and 23). But 
individuals of either kind, pistils or stamens, may unite in a group 
of considerable numbers or again, pistils and stamens may grow 
together in the same group (Fig. 24). There may be a single 
stamen and a single pistil or a single pistil with several stamens 
or there may be several of each in association within the same flower. 
Examples in which many staminate flowers are found in one 
group and many pistillate flowers in another are found in the 
