It would be impossible to give even an approximate idea of the diversity of the contrivances for securing fertilization in flowers without spending many hours over them, for they are different in almost every flower, often widely so, and even in species of the same genus they are by no means always alike; for not infrequently one species is adapted to one circle of visitors, and its near relative to another. Thus the flower of the common Daphne (_Daphne mezereum_) (Fig. 45, _A_ and _C_) is adapted to the visits of butterflies, bees, and hover-flies, while its nearest relative (_Daphne striata_) (Fig. 45, _B_ and _D_) has a somewhat narrower and longer corolla-tube, so that only butterflies can feast upon it. This example shows that there are exclusively 'butterfly flowers,' but specialization goes further, for there are flowers adapted to diurnal and others to nocturnal Lepidoptera. The former have usually bright, often red colours, and a pleasant aromatic fragrance, and in all of them the nectar lies at the bottom of a very narrow corolla-tube. To this class belong, for instance, the species of pink, many orchids, such as _Orchis ustulata_, and _Nigritella angustifolia_ of the Alps, which smells strongly of vanilla; also the beautiful campion (_Lychnis diurna_) and the Alpine primrose (_Primula farinosa_). The flowers adapted to nocturnal Lepidoptera are characterized by pale, often white colour, and a strong and pleasant smell, which only begins to stream out after sunset, and indeed many of these flowers are quite closed by day. This is the case with the large, white, scentless bindweed (_Convolvulus sepium_), which is chiefly visited and fertilized by the largest of our hawk-moths (_Sphinx convolvuli_). The pale soapwort (_Saponaria officinalis_) exhales a delicate fragrance which attracts the Sphingidæ from afar, and the sweet smell of the honeysuckle (_Lonicera periclymenum_) is well known, and has the same effect; an arbour of honeysuckle often attracts whole companies of our most beautiful Sphingidæ and Noctuidæ on warm June nights, to the great delight of the moth-collecting youth. [Illustration: FIG. 45. _Daphne mezereum_ (_A_ and _C_) and Daphne striata (_B_ and _D_). The former visited by butterflies, bees, and flies, the latter by butterflies only. _A_ and _B_, vertical sections of the flowers. _St_, stamens. _Gr_, style. _n_, nectary. _C_ and _D_, flowers seen from above. After H. Müller.]