vr THE SPKEADING OF FOOD-PLANTS 67 



plant that it is necessary to have varieties which 

 can be grown in all kinds of climates. 



One very important point about alfalfa as com- 

 pared, for instance, with some clovers is that it is 

 perennial, that is, comes up year after year. The 

 result is that where the winter is short and mild it 

 can be made to furnish a great many cuttings of 

 hay. It grows to a certain height and then is cut 

 down, but if the fine weather continues, and water 

 is supplied, it grows again and gives another crop, 

 and so on, until it seems like a veritable gold-mine 

 to the farmer. 



But most strains of alfalfa are tender plants ; 

 they require a moderately warm climate, and 

 are readily killed by winter frosts. This is 

 a great loss to the farmer, who in many regions 

 is dependent on the alfalfa crop to feed his 

 beasts. Therefore the Bureau of Plant Industry 

 has made a series of very elaborate experiments 

 on different kinds of alfalfa, so as to try to find 

 kinds suitable to all the different climates of the 

 dry regions of the United States. It is not possible 

 here to describe anything like all these experiments ; 

 let us take an example to show the kind of work 

 that has to be done, and the usefulness of the 

 work. 



During the experiments, alfalfas were collected 

 from all the different parts of the world where they 



