OPENING OF THE PASSAGE TO THE INTERIOR OF THE FLOWER. 209 



small nocturnal moths, and give off no scent during the day, but exhale a strong 

 Hyacinth odour at twilight. Similarly the flowers of the common Dame's Violet 

 (Hesperis miati'onalis) smell like Violets in the evening, and those of a species of 

 Woodruff" (As2yerula capitata) smell of vanilla as darkness approaches. On the 

 other hand, many flowers visited during the day by butterflies, bees, and humble- 

 bees become scentless at sunset. The yellow flowers of Spartium scopariwm only 

 exhale their exquisite acacia scent when the sun is high and the insects named are 

 swarming through the warm air. In the evening there is no trace of the scent. 

 The ornamental Clover, Trifoliuon resupinatura, whose flowers are surrounded by 

 bees, smell strongly of honey in the sunshine, but become scentless as soon as the 

 bees return to their hive at twilight. The same is true of the Grass of Parnassus 

 {Pamassia palustris), which only smells of honey in bright sunshine and becomes 

 scentless in the evening. A species of Daphne growing in the Pyrenees {Daphne 

 Philippi) liberates a delicate scent of Violets during the day, only ceasing to smell 

 when night falls. 



It is sometimes suggested that colour and scent in flowers to some extent 

 mutually exclude one another, so that in cases where the allurement of honey- and 

 pollen-eating insects is brought about by the bright colour of the corolla, the scent 

 is absent, and vice versa. This idea is supported by the facts that many flowers 

 with brilliant colouring, which can easily be seen at a distance on account of their 

 large size, have no scent, e.g. the flowers of the Cornflower (Centaurea Cyamis), the 

 Pheasant's Eye (Adonis castivalis and ßaTnniea), many Gentians (Gentiana acaulis, 

 Bavarica, verna), various species of Lousewort (Pedicularis incamata, rostrata, 

 &c.), the Cam^ellia (Camellia Japonica), the Indian Azalea (Azalea Indica), and 

 numerous species of Amaryllis and Hemerocallis] whilst, on the other hand, many 

 plants with small and insignificant flowers, as, for example, the Mignonette (Reseda 

 odorata), the Vine (Vitis vinifera), the Ivy (Hedera Helix), Gleditschia (Gleditschia 

 triacanthos), and Eleagnus (Eleagnus angustifolia) give off" a strong scent which 

 can be perceived at some distance. It might be also pointed out that the oft- 

 mentioned Pelargoniums (Pelargonium, atrum and triste) and Hesperis tristis, 

 which bear dirty yellow and dark flowers, indistinguishable to the best sight in 

 twilight, develop a strong Hyacinth odour, which allures numerous small night- 

 flying Lepidoptera. But however conclusive these examples may be, there are 

 many others of the opposite kind, i.e. of bright and noticeable colours, occurring not 

 infrequently in conjunction with strong scents. Roses, Pinks, and Stocks, many 

 tropical Orchids, Magnolias, Narcissi and the large-flowered Rhododendrons of the 

 Himalayas show at least that the view mentioned has not a universal application. 



OPENING OF THE PASSAGE TO THE INTERIOR OF THE FLOWER. 



The removal and transmission of pollen by animals can obviously only take 

 place when the perianth-leaves, under whose protection the pollen and stigmas are 

 matured, permit of access to the base of the flower. I have altered the usual 



VOL. II. 64 



