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 insects that most abound where they grow. Thus the gentians of the lowlands are adapted to bees, those of the high alps to butterflies only; and while most species of Rhinanthus (a genus to which our common "yellow rattle" belongs) are bee-flowers, one high alpine species (R. alpinus) has been also adapted for fertilisation by butterflies only. The reason of this is, that in the high alps butterflies are immensely more plentiful than bees, and flowers adapted to be fertilised by bees can often have their nectar extracted by butterflies without effecting cross-fertilisation. It is, therefore, important to have a modification of structure which shall make butterflies the fertilisers, and this in many cases has been done.

9. Economy of time is very important both to the insects and the flowers, because the fine working days are comparatively few, and if no time is wasted the bees will get more honey, and in doing so will fertilise more flowers. Now, it has been ascertained by several observers that many insects, bees especially, keep to one kind of flower at a time, visiting hundreds of blossoms in succession, and passing over other species that may be mixed with them. They thus acquire quickness in going at once to the nectar, and the change of colour in the flower, or incipient withering when fertilised, enables them to avoid those flowers that have already had their honey exhausted. It is probably to assist the insects in keeping to one flower at a time, which is of vital importance to the perpetuation of the species, that the flowers which bloom intermingled at the same season are usually very distinct both in form and colour. In the sandy districts of Surrey, in the early spring, the copses are gay with three flowers—the primrose, the wood-anemone, and the lesser celandine, forming a beautiful contrast, while at the same time the purple and the white dead-nettles abound on hedge banks. A little later, in the same copses, we have the blue wild hyacinth (Scilla nutans), the red campion (Lychnis dioica), the pure white great starwort (Stellaria Holosteum), and the yellow dead-nettle (Lamium Galeobdolon), all distinct and well-contrasted flowers. In damp meadows in summer we have the ragged robin (Lychnis Floscuculi), the spotted orchis (O. maculata), and the yellow rattle (Rhinanthus