GRASSES OF BRITAIN. XV 



for two or three years more, it is possible that each succeeding year 

 may enrich the surface soil as much as the roots and stubble of the 

 first year's hay had done ; so that if it lay three years it might ob- 

 tain three times the amount of improvement. This is owing to the 

 circumstance that the whole produce of the field remains upon it, 

 except what is carried off by the stock when removed — but very 

 much, it is obvious, will depend upon the nature of the soil and 

 upon the selection of the seeds being such, as to secure a tolerable 

 produce of green food during the second and third years. 



" Permanent ■pasture or meadoio. — But when land is laid down 

 to permanent grass it undergoes a series of further changes, which 

 have frequently arrested attention, and which, though not difficult to 

 be understood, have often appeared mysterious and perplexing to 

 practical men. Let us consider these changes. 



" When grass seeds are sown for the purpose of forming a per- 

 manent sward, a rich crop of grass is obtained during the first, and 

 perhaps also the second year, but the produce after three or four 

 years lessens, and the value of the pasture diminishes. The plants 

 gradually die and leave blank spaces, and these again are slowly fill- 

 ed up by the sprouting of seeds of other species, which have either 

 lain long buried in the soil or have been brought thither by the 

 winds. 



" This first change, which is almost universally observed in fields 

 of artificial grass, arises in part from the change which the soil it- 

 self has undergone during the few years that have elapsed since the 

 grass seeds were sown, and in part from the species of grass select- 

 ed not being such as the soil, at any time, could permanently sus- 

 tain. 



" When this deterioration, arising from the dying out of the 

 sown grasses, has reached its utmost point, the sward begins gradu- 

 ally to improve, natural grasses suited to the soil spring up in the 

 blank places, and from year to year the produce becomes greater 

 and greater, and the land yields a more valuable pasture. Practical 

 men often say that to this improvement there are no bounds, and 

 that the older the pasture the more valuable it becomes. 



" But this is true only w'ithin certain limits. It may prove ti-ue for 

 the entire currency of a lease, or even for the lifetime of a single ob- 



