FOLIAGE. 157 



factured by plants. It is not, of course, possible for 

 any domestic animal to utilise all the vegetable matter 

 grown upon any particular area, but a very rough idea 

 of the work produced by plants can be obtained as 

 follows : — A cart horse will require (from data kindly 

 given me by Principal M'Call, LL.D.), some i 2 lbs. of 

 oats, I 8 lbs. of hay, and 2 lbs. of bran every day. This 

 means that at the average annual return in Britain, 

 some 4^ acres must be set aside for its support. It is 

 probable that, even the 1500 hours of sunshine which 

 would fall on 4 1 acres in Britain, is theoretically capable 

 of doing the work of 3000 cart horses. 



This does not seem to be very satisfactory ; but it 

 must be remembered that the oats, the hay, and even 

 the cart horse, have been artificially selected by man, 

 who has, in agriculture, the very roughest general idea 

 as to what he is about. 



This view of leaves as subservient to man, the more 

 or less intelligent agriculturalist, is very decidedly 

 necessary in any study of foliage, as it is, indeed, in 

 each department of Nature study. 



