to the further conclusion: 'If the corolla has a particular colour in particular spots on account of the insects, it is for
the sake of the insects that it is so coloured; and if the
particular colour of a part of the corolla serves to show an
insect which has lighted on the flower the direct path to the
juice, the general colour of the corolla has been given to it, in
order that insects flying about in search of their food may see
the flowers that are provided with such a corolla from a long
distance, and know them for receptacles of juice.'
He afterwards discovered that the stigmas of a species of Iris were absolutely unable to be fertilised in any other way than by insects, and further observation convinced him more and more, 'that many, perhaps all flowers, which have this juice, are fertilised by the insects which feed on it, and that consequently this feeding of insects is in respect of themselves an end, but in respect of the flowers only a means, but at the same time the sole means to a definite end, namely, their fertilisation; and that the whole structure of such flowers can be explained, if in examining them we keep in sight the following points, first, that flowers were intended to be fertilised by the agency of one or another kind of insects, or by several; secondly, that insects in seeking the juice of flowers, and for this purpose either alighting upon them in an indefinite manner, or in a definite manner either creeping into them or moving round upon them, were intended to sweep off the dust from the anthers with their usually hairy bodies or with some part of them, and convey it to the stigma, which is provided either with short and delicate hairs, or with a viscid moisture, that it may retain the pollen.'
In the summer of 1790 he detected dichogamy, which he first observed in Epilobium angustifolium. He found, 'that these hermaphrodite flowers are fertilised by the humble-bee and by other bees, and that the individual flower is not fertilised by its own pollen, but the older flowers by the pollen which the insects convey to them from the younger.' Having
