106 PLANT LIFE OK THE FARM. 



in a mixed manure a particular effect is due, and to ob- 

 tain confirmation of the results obtained by other 

 methods. By adding or by withholding a particular salt, 

 as the case may be, an answer to the question proposed 

 may be obtained. In the following paragraphs the effects 

 of the disuse of certain manures, and then of the substi- 

 tution of one kind for another, will be very briefly allud- 

 ed to. 



Disuse of Manure of any Kind. On a plot to which 

 farm-yard manure was applied it was observed that while 

 the produce was largely increased, more so indeed than 

 under almost any other circumstances, the per-centage 

 of grasses and of some of the miscellaneous weeds was 

 increased, while the leguminous herbage was diminished. 

 On discontinuing the dung the vegetation of the plot 

 was observed gradually but uniformily to approximate 

 to that of the unmanured plot, the number of species 

 increasing without any marked preponderance of any, 

 and good grasses like Poa trivialis giving place to poorer 

 ones, such as Festuca ovina. 



Disuse of Farm-yard Manure. Another plot which 

 originally received a combination of dung and ammonia, 

 has been treated since 1864 with a small dose of ammonia 

 salts only. Here the grasses and the Leguminosse are 

 diminishing as to numbers, but the luxuriance of those 

 species that remain is increased. The miscellaneous 

 weeds, especially Rumex Acetosa, and the Composites, 

 are decreasing, Ranunculacece decline, and even more 

 markedly so the Umbelliferce and Plantago lanceolata, 

 the latter plant being very sensitive to ammonia. 



Disuse of Potash, The first effect noticeable after 

 the disuse of potash was a diminished produce of grasses. 

 Leguminosae have also continuously and strikingly deT 



