THE ADAPTATION OF THE PLANT TO THE SOIL. 



5 



or two other cases of association; for example, the sorrel {Rumex 

 Acetosa) is abundant on all plots which receive potash and have 

 their soil in an acid condition. This we can associate with the fact 

 that the sap of the sorrel plant is strongly acid, and that the acid 



Fig. 4. — Turf frOxM the Plot receiving a complete Manure containing 



LARGE quantities OF NiTROGEN, PHOSPHATES AND PoTASH, 



No weeds. 



consists of a compound of potash, the acid oxalate. There are, how- 

 ever, many more problems than answers to be found in these plots. 

 For example, why does the grass Briza media and the Eosaceous plant 

 "Burnet " turn up on the unmanured plots, and there only? Why 

 is the umbelliferous plant Ayitliriscus sylveslris abundant on plots 

 receiving nitrate of soda, whereas in Nature it only occurs in hedge- 



