288 GENERALIZATIONS. 



All these facts afford arguments against a slow and uniformly 

 progressive transformation of species, and lead to the conclusion 

 that the transformation of organic nature took place in a period 

 of comparatively limited duration. For thousands of years the 



the others. A botanist whose sagacity in other respects is generally admitted^ 

 having adopted these notions, has even maintained that all the beautiful 

 ornaments of flowers would gradually disappear, and that all plants would 

 have none but small green flowers, if the class of insects should be lost. The 

 erroneous nature of any such proposition is demonstrated by what takes place 

 in the Arctic zone, and in the high chains of the Swiss Alps ; flower-loving 

 insects are altogether wanting (as at Spitzbergen), or occur in such small 

 numbers that their influence upon flowers must be very restricted. The 

 flowers there ought consequently to have no colours ; for there is no doubt 

 that in Spitzbergen, where there are no insects frequenting the flowers, the 

 present state of things has existed since the drift-epoch. Facts prove, 

 with respect to colour and size, that the plants of the high Alps are 

 distinguished from those of the plain by the brighter colours and larger 

 dimensions of their flowers. Spitzbergen also possesses a considerable 

 number of plants with fine flowers ; and the same remark applies to Nova 

 Zembla. Insects are not much attracted by the form, colour, and size of 

 flowers, but almost entirely by the honey that they contain ; for it is 

 principally the sense of smell, and not the eyes, that guides them towards 

 flowers. The plants with the smallest and least-striking flowers, such as the 

 willow, the maple, and the lime-tree, are those most sought by bees, whilst 

 plants with brilliant flowers, such as the tulip, are not visited by them. 

 There are a great number of species of willows ; but, notwithstanding the 

 assiduity with which they are visited by insects, not one of these species has 

 succeeded in surrounding its flowers even with a green calyx. The limes 

 also are obliged to content themselves with a small whitish corolla. Every 

 bee-keeper knows that it is the sweet odour of honey alone that attracts 

 these insects ; and hence they make their way in masses towards sugar-refine- 

 ries, even at great distances, and often perish there in great numbers. They 

 scent the honey even where they cannot see it, and seek by every means to 

 get at it. Within the last few years a new species of larkspur (Delphinium 

 macranthum) has been introduced into the Swiss gardens. The spur of this 

 plant is so long that the proboscis of the humble-bees cannot reach the honey 

 at the bottom of it. The humble-bees merely cut a hole in the spur, and 

 pass the proboscis through it; by this means they attain their object. For 

 the last two years Prof. Heer has observed, in the Zurich Botanic Garden, 

 that all the humble-bees procure the honey of this species of larkspur by 

 holes made as he has just described, whilst other insects with a longer trunk^ 

 such as the Macroglossa stellatarum, push their proboscis in by the ordinary 

 course from the corolla. 



