108 PLANT LIFE OH THE FARM. 



has been the most prominent grass, while Laihyrus pra- 

 tensis has manifested considerable increase, and Rumex 

 Acetosa has been the most prominent among the miscel- 

 laneous plants. 



The greatest change after some years was, however, 

 not in the distribution of the species, but rather in the 

 character of their development and their increased 

 tendency to form stem and seed. 



Summary. From the foregoing details it is manifest 

 that the plants found on the several plots vary very 

 greatly in number, in character, and in degree of de- 

 velopment, according to the nature of the manurial 

 agent employed, the ever varying character of the sea- 

 sons, and the association or hostile competition of their 

 neighbors. These several conditions rarely, if indeed 

 ever, act singly, but almost always in combination. Cir- 

 cumstances are never exactly twice alike ; a condition of 

 absolute equilibrium is never attained. The nearest ap- 

 proach to it has been reached in the case of the unma- 

 nured plot on the one hand, and of the very highly ma- 

 nured plots on the other, but these, like the others, are 

 influenced by climatal changes occurring now at one 

 stage of growth, now at another. And even when a 

 comparative state of equilibrium is attained, very slight 

 causes, even such as may be roughly called accidental, as 

 the injuries inflicted by insects, or parasitic fungi, suffice 

 to disturb the balance and bring about a different arrange- 

 ment and proportion of species, and a corresponding 

 change in the development of individual plants. 



As to the action of manures on the plants, it is com- 

 paratively rarely that they are employed in such quanti- 

 ties as to be absolutely destructive or poisonous. In most 

 cases even when a particular manure is proved to be 

 more or less directly injurious to particular plants the 

 indirect harm accruing from the beneficial action of the 



