16 THE WORLD OF LIFE chap. 



Another point of some importance is the greater stability 

 in the flora of meadow as compared with that of pasture 

 land. In the former only one plant was an accidental 

 straggler, while in the latter there were 12, or two-thirds of 

 the peculiar species. These are mostly rare, and are very often 

 not truly British plants, so that they cannot be considered 

 as permanent pasture plants. The more stable meadow 

 flora is no doubt largely due to the fact that few of the late- 

 flowering plants are allowed to produce seed, and though 

 seed may be often introduced by birds or the wind, many 

 of these species soon die out. It thus appears that though 

 pastures are actually richer in species than meadows, yet the 

 latter have a more permanent character, as almost all those 

 peculiar to pastures are comparatively rare and therefore 

 very liable to disappear through very slight changes of 

 conditions. 



These various facts, and many others which cannot be 

 here given, serve to show us how very delicate are the 

 mutual relations and adjustments of plants to their total 

 environment. In proportion as that environment is subject 

 to change of any kind, some rare species die out, while others 

 become diminished in numbers. And what takes place in 

 single fields or other small areas, when closely studied, must 

 certainly occur on a much grander scale over the whole 

 earth, and especially in those countries and periods when 

 great changes of climate or of physical geography are taking 

 place. These detailed studies of " Meadow and Pasture 

 Analysis" — as their author terms them — thus demonstrate 

 on a very small scale that " struggle for existence " which, as 

 we shall see further on, is always present, acts in an almost 

 infinite number of ways, and is one of the most important 

 factors in the developmental changes of the World of Life. 

 We will now proceed to give some of the numerical facts of 

 plant distribution, in various areas small and large, as well 

 as over the whole earth ; but it will be advisable first to 

 give a brief account of the way in which this is usually 

 dealt with by botanists. 



Four years before the appearance of the Origin of 

 Species the great Swiss botanist, Alphonse De Candolle, 

 published one of the most remarkable and interesting 



