namely, 14.6 per cent; of red, only 8.2 per cent are odoriferous. (10/4.  The colours and odours of the flowers of 4200 species have been tabulated by Landgrabe and by Schubler and Kohler.  I have not seen their original works, but a very full abstract is given in Loudon’s ‘Gardeners’ Magazine’ volume 13 1837 page 367.) The fact of a larger proportion of white flowers smelling sweetly may depend in part on those which are fertilised by moths requiring the double aid of conspicuousness in the dusk and of odour.  So great is the economy of nature, that most flowers which are fertilised by crepuscular or nocturnal insects emit their odour chiefly or exclusively in the evening.  Some flowers, however, which are highly odoriferous depend solely on this quality for their fertilisation, such as the night-flowering stock (Hesperis) and some species of Daphne; and these present the rare case of flowers which are fertilised by insects being obscurely coloured.

The storage of a supply of nectar in a protected place is manifestly connected with the visits of insects.  So is the position which the stamens and pistils occupy, either permanently or at the proper period through their own movements; for when mature they invariably stand in the pathway leading to the nectary.  The shape of the nectary and of the adjoining parts are likewise related to the particular kinds of insects which habitually visit the flowers; this has been well shown by Hermann Muller by his comparison of lowland species which are chiefly visited by bees, with alpine species belonging to the same genera which are visited by butterflies. (10/5.  ‘Nature’ 1874 page 110, 1875 page 190, 1876 pages 210, 289.) Flowers may also be adapted to certain kinds of insects, by secreting nectar particularly attractive to them, and unattractive to other kinds; of which fact Epipactis latifolia offers the most striking instance known to me, as it is visited exclusively by wasps.  Structures also exist, such as the hairs within the corolla of the fox glove (Digitalis), which apparently serve to exclude insects that are not well fitted to bring pollen from one flower to another. (10/6.  Belt ’The Naturalist in Nicaragua’ 1874 page 132.) I need say nothing here of the endless contrivances, such as the viscid glands attached to the pollen-masses of the Orchideae and Asclepiadae, or the viscid or roughened state of the pollen-grains of many plants, or the irritability of their stamens which move when touched by insects etc.—­as all these contrivances evidently favour or ensure cross-fertilisation.

All ordinary flowers are so far open that insects can force an entrance into them, notwithstanding that some, like the Snapdragon (Antirrhinum), various Papilionaceous and Fumariaceous flowers, are in appearance closed.  It cannot be maintained that their openness is necessary for fertility, as cleistogene flowers which are permanently closed yield a full complement of seeds.  Pollen contains much nitrogen and phosphorus—­the