112 PLANT LIFE ON THE FARM. 



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 Leguminosae 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 de- 

 creasing, Ranunculacece decline, and even more markedly 

 so the Umbellifera 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 de- 

 creased, while miscellaneous plants, especially Achillea 

 Millefolium and Rumex Acetosa, have increased. 



The increase of Festuca ovina is probably not so much 

 due to any favouring effect of the manure as to the en- 

 feeblement of its competitors. Anthoxanthum odoratum 

 has increased, but almost all the other grasses have 

 diminished. Ranunculacece, Composite, especially Achil- 

 lea, have increased since the disuse of potash. Umbel- 

 lifers, Plantago lanceolata, and Rumex Acetosa have 

 decreased. 



On the plot where ammonia is added to mineral manures, 

 but where potash is omitted, the grasses show a large per- 

 centage from the effect of the ammonia ; the leguminous 

 plants are almost banished, owing to the combination of 

 unfavourable circumstances, i.e. the presence of ammonia 



