92 BOARD OF AGRICULTURE. 



ments of the crop should determine the rotation. Of course 

 there are other conditions to be taken into account in prac- 

 tice. Winter wheat, for example, cannot follow itself beyond 

 a certain length of time, even if the soil will allow, because 

 the land ordinarily becomes foul with weeds; and it is better 

 to alternate with some crop whicli will enable us to destroy 

 the weeds by hoeing or which will choke them out directly. 

 There are many conditions which influence rotation that I do 

 not propose to speak of, but I shall confine myself to that 

 part of the subject which is involved in the feeding of the 

 plant. The broadest principle of rotation is to alternate 

 grain crops with forage crops. That is-, to follow plants hav- 

 ing a short and rapid growth and which produce seed, by plants 

 of a longer period of growth which are not allowed to ripen 

 seed, but are harvested for their large amount of foliage. 



Plants, like animals, have different ways of feeding. If 

 you were to undertake to keep a dairy of hyenas you would 

 have to provide a different food from that which you give to 

 cows. If you should choose the giraffe as a domestic animal 

 you would find that its habits of feeding are adapted to very 

 different circumstances from those of your common pastures. 

 The natural food of the giraffe is mainly the buds and twigs of 

 a kind of locust tree that grows in the African wilderness, and 

 the long fore-legs and long neck of the animal are shaped 

 for browsing among the fops of those trees. The different 

 classes of plants have peculiarities in their feeding arrange- 

 ments which are as marked and striking as these differences 

 in animals. 



On comparing together the roots of our ordinary crops, we 

 find that when they grow under similar circumstances there 

 is a great difference in the depth to which they extend, a 

 great difference in the degree in which they branch, and a 

 great difference in the absolute quantity of roots. Unfortu- 

 nately, we have not enough really satisfactory observations on 

 these points to serve us in any very extended comparison, it 

 being rather troublesome to make accurate observations of 

 the roots of plants when they have once penetrated the soil. 

 A few brief paragraphs in my book " How Crops Grow," em- 



