34:0 The Effect of Potassivin Salts on Dactylis glomerata 



of potash was accompanied by a reduction in the thickness of the walls, 

 and an increase in the diameter of the lumen. Vogeler and Thielei") 

 obtained inconclusive results. 



Dassonville(8) investigated the effect of mineral salts on many 

 plants, using both water cultures and pot-cultures in his experiments. 

 He grew plants in culture solutions containing potassium chloride side 

 by side with those in which this salt had been replaced by sodium 

 chloride. With potasisium chloride the plants grew much more vigor- 

 ously than with the sodium salt, but in the case of grasses and cereals, 

 the lowest internode was so weak that the plant fell, while those with 

 sodium chloride were still standing. This he attributed to a weakening 

 effect of potassium salts. Sections revealed more intense lignification in 

 plants grown without potassium chloride. This result is clearly not in 

 accordance with the facts observed in the field, and cannot, therefore, 

 be accepted as final. Dassonville himself found that the stunted plants 

 grown in distilled water showed the most intense lignification of all. 



This last result of Dassonville suggests that starvation promotes 

 rapid lignification in the young stages, possibly because reserves of 

 carbohydrates in the seed go to form cell-wall material in the absence 

 of minerals necessary for the formation of proteins. It may be then 

 that the thickening of plants in the sodium chloride culture solution is 

 due to starvation rather than to the effect of sodium itself. The unusual 

 weakness of the plants which were supplied with potash was presumably 

 due to the unsuitability of the solution Dassonville used for cereals; 

 barley grown in the stronger solution used at Rothamsted has never 

 been known to collapse, and can be brought to fruit, while .specimens 

 of Lolium perenne have been growing in the Rothamsted solution for 

 more than eight months, and many of them are still perfectly healthy. 



It may be that the effect of potassium salts varies with the period 

 of growth — that one result would be obtained early in the life of the 

 plant, but a totally dift'erent one later. Dassonville examined his plants 

 at one stage only — the time was determined by the collapse of his plants. 



During the summer of 1917 the effect of potassium salts on the ana- 

 tomy of Dactylis was investigated, and the results are set out in this 

 paper. Plants were collected both from field plots which had received 

 potassium fertilisers, and from those which had not. The potassium 

 salts in the soil were sufficient to prevent complete potash starvation 

 where no such salts had been added, so that one difficulty of Dassonville's 

 experiments was removed. Moreover, material was collected at short 

 intervals during the summer, from the time when flowering stems were 



