THE FLOWER (SCENT) 
89 
as extra protections, e.g. in Geranium sylvaticum , Malva, 
Swertia,- &c. The stamens, or parts of them, cover the 
honey in Campanulaceae, &c., and so on. In many plants 
there is no free honey, but insects (especially bees) bore into 
certain succulent tissues and suck the sap. Interesting 
examples are found in Orchis and many other Orchidaceae, 
Liliaceae (e.g. Brodiaea), &c. 
A few flowers, e.g. Dalechampia, attract insects by 
providing resin or other useful substances. 
Attraction of insects from a distance is largely, so far as 
we can tell, the function of the brightly coloured corolla 
(see Colours of Flowers, below) ; in some cases there is a 
coloured calyx or bracts, or the stamens are exposed, as in 
many Acacias, Callistemon, &c. The conspicuousness 
is often increased by massing of the flowers (p. 66). 
Whilst conspicuousness and colour are doubtless great 
attractions to insects, scent is even more powerful, as a 
consideration of such cases as Convolvulus arvensis and 
Calystegia sepium will show, and as is evidenced also by the 
great number of visitors received by many sweetly-scented 
and inconspicuous flowers. It is necessary to remember 
the limitation of our own sense of smell, and not to con- 
clude that because we cannot smell it, a flower has no scent. 
There are several experiments tending to show that bees 
can smell flowers which to us seem scentless. The carrion 
smell of such flowers as Arum, Stapelia, &c. repels all 
visitors but the carrion-loving flies, by which alone these 
flowers are visited and pollinated. 
Insects, especially small flies, often visit flowers for 
shelter, chiefly such as hang downwards or have hooded 
corollas, and in this way a certain amount of pollination is 
probably effected. 
One great direction followed in evolution has been 
the formation of tubular structures in flowers, narrowing the 
entrance to the honey. A simple flower, hypo-, peri-, or epi- 
gynous with a convex or flat torus, and without concrescence 
of its organs, usually has its honey freely exposed, so that 
it may be licked by the shortest-tongued insects. Many 
flowers of this kind exist, and form a biological class, “flowers 
with freely exposed honey.” It is termed for brevity class A, 
and contains such flowers as those of species of Saxifraga, 
