92 HOUSE, GARDEN, AND FIELD 



By the discouragement of many species which are either 

 unprofitable to man, or unable to withstand under artificial 

 conditions the competition of the introduced and selected 

 species which thrive by cultivation, the flora of the wastes 

 has come to appear more alpine and arctic than it really is. 

 Even now, if cultivation were to cease ; if the streams 

 were again to become choked with swamps ; if the im- 

 ported species were no longer favoured by manuring and 

 cropping ; we should probably see many species of plants 

 descend from the barren hill-tops, to establish themselves 

 in the plains or on the lower hills. The process, by which 

 during the period of scientific observation these denizens 

 of the wilderness have been ousted from many spots where 

 they used to thrive, would be reversed, and such reversal, 

 if carried far, would give such an extension to the flora 

 which we call alpine or arctic, as we should expect to 

 result from a great fall in mean annual temperature. 



I do not believe that we need call in the glacial period 

 to explain the present distribution of European plants. 

 With or without a glacial period we should have had, under 

 present conditions of climate and tillage, a great contrast 

 between the cultivated land and the wastes ; the wastes 

 would, as now, occupy the far north and the highest ground 

 of central Europe ; there would be species common to both 

 areas which no longer occur in the interjacent lands. To 

 explain the identity of the arctic and alpine floras by means 

 of the glacial period is to explain by a well- ascertained 

 fact a coincidence which is not yet established. Before 

 we ask what is the cause of the identity of the arctic and 

 alpine floras, let us ask whether they are truly identical. 



XVIII. WATER-LILIES. 



Whenever I wish to refresh my recollection of the 

 common water-lilies, I can do so by means of a very 

 pleasant little excursion. A few miles from the busy 



