158 ON BIO-GEOLOGY. [vu. 



puffin turns out the old rabbits, eats the young ones, 

 and then lays her eggs in the rabbit-burrow simply 

 because she can. 



Now, you will see at once that such a course of 

 questioning will call out a great many curious and 

 interesting answers, if you can only get the things to 

 tell you their story ; as you always may if you will 

 cross-examine them long enough; and will lead you 

 into many subjects beside mere botany or entomology. 

 So various, indeed, are the subjects which you will 

 thus start, that I can only hint at them now in the 

 most cursory fashion. 



At the outset you will soon find yourself involved in 

 chemical and meteorological questions ; as, for instance, 

 when you ask How is it that I find one flora on the 

 sea-shore, another on the sandstone, another on the 

 chalk, and another on the peat-making gravelly strata ? 

 The usual answer would be, I presume if we could 

 work it out by twenty years' experiment, such as 

 Mr. Lawes, of Rothampsted, has been making on the 

 growth of grasses and leguminous plants in different soils 

 and under different manures the usual answer, I say, 

 would be Because we plants want such and such 

 mineral constituents in our woody fibre ; again, because 

 we want a certain amount of moisture at a certain 

 period of the year : or, perhaps, simply because the 

 mechanical 'arrangement of the particles of a certain soil 

 happens to suit the shape of our roots and of their 

 stomata. Sometimes you will get an answer quickly 

 enough; sometimes not. If you ask, for instance, 

 Asplenium viride how it contrives to grow plentifully 

 in the Craven of Yorkshire down to 600 or 800 feet 

 above the sea, while in Snowdon it dislikes growing 



