342 The Effect of Potass mm Salts on Dactylis glomerata 



sium salts on the stems of grasses is not due to their influence on the 

 structure of the mechanical tissues, and that potash has some other 

 effect on the j^lant to which this strengthening must be attributed. 



PART II. EXPERIMENTAL IMETHODS. 



The plant selected for this investigation was Dactylis glomerata. 

 This grass is a fairly common constituent of the hay from all the grass 

 plots at Eothamsted from which material was collected', and it puts 

 up a stout flowering stem from which suitable sections for investigation 

 could easily be cut. Its stem structure is, moreover, typical of the 

 Gramineae and it is among cereals and grasses that lodging takes place 

 to a serious extent. 



The material was collected from plots which had been receiving the 

 following manurial treatments for nearly sixty years. 



Plot Manure (NHjloSO^ Super- KoSO, Na,SOi MgSO, 



phosp. 

 lbs. cwts. lbs. lbs. lbs. 



7 Complete minerals — 3-5 500 100 100 



8 Minerals without 1 



potassium salts 



3-5 — 250* 100 



9 Complete minerals | ^^^ 3.5 g^^ jq^ ^^^ 



+ ammonium salts j 



10 Minerals without ) 



potassium salts [ 400 3-5 — 250* 100 



+ ammonium salts ) 



* Reduced to 100 lbs. in 1905. 



With this material it was possible to investigate the effect of potas- 

 sium salts both in the presence and absence of nitrogenous manures. 



The effect of jjotash manures in preventing lodging is well exemplified 

 on the grass plots. Frequently the grass on plots without potash, such 

 as 8 and 10, was completely flattened, while that on the neighbouring 

 plots 7 and 9 was still standing. 



If, then, this effect is actually due to the influence of potash on the 

 anatomy, plants from these plots should show marked anatomical 

 differences. 



The summer of 1917, when this investigation was carried out, was 

 remarkably dry during the growing period of the hay, and it was not 

 until a few days before it was cut that heavy rains caused a certain 

 amount of lodging to take place. 



1 Attempts were made to procure material from plants grown in water cultures, but 

 under these conditions no flowering stem was formed. 



