94 GRASSES AND FORAGE PLANTS. 



grasses, is now not only extensively cultivated, bnt is found to 

 be one of the most valuable and economical forage plants. It 

 belongs to the pulse family, or leg-iiminosce, which includes the 

 larger portion of forage plants called artificial grasses, in dis- 

 tinction from the graminess, the true, and often called the 

 natural grasses. The generic name, trefoil, or trifolium, is 

 derived from the Latin ires, three, and folium, a leaf ; and the 

 genus can generally be Tery readily distinguished by the num- 

 ber and arrangement of its leaves in three leaflets, and flowers 

 in dense, oblong or globular heads. 



Specific description : Stems ascending, somewhat hairy, leaf- 

 lets oval or obovate, often notched at the end and marked on 

 the upper side with a pale spot, heads ovate and set directly 

 upon the stalk instead of upon branches. This species is 

 regarded as by far th6 most important of the whole genus. It 

 has sported into a number of varieties, one of which is biennial, 

 another perennial, the latter by long cultivation becoming 

 biennial, while the former,— as is true of most biennial and 

 many annual plants, — assumes, to some extent, the character of 

 a perennial and can be made to last three or four years or even 

 more, by simply preventing it from running to seed. This 

 plant is seen in Fig. 86, its leaf is shown in Fig. 87, and its 

 fruit magnified in Fig. 88. 



The introduction of clover into England, it is often said, 

 produced an entire revolution in her agriculture, and indeed, 

 when we consider how important a part it plays in our own 

 system of farming, we can with difficulty imagine how our 

 ancestors ever got on at all in farming without it. Be this as it 

 may, it is certain that it led to many of the most important 

 improvements in the rotation of crops. Clover is very properly 

 regarded as a fertilizer of the soil. The action of its long and 

 powerful tap roots is not only mechanical, — loosening the soil and 

 admitting the air, — but also chemical, serving to fix the gases 

 important to enrich the earth, and when these roots decay they 

 add largely to that black mass of matter we call the soil. It 

 serves, also, by its luxuriant foliage, to destroy annual weeds 

 which would spring Tip on newly seeded land, especially after 

 imperfect cultivation. But one of the most valuable uses of 

 it, and one too often overlooked, is to shade the surface and 

 tlicrcljy increase its fertility. 



