10 



If this view is correct it follows that acids need not be used in 

 soil analysis at any rate for the extraction of bases : any agent 

 capable of being absorbed by the soil would serve equally well. In 

 our laboratory Mr. J. A. Hanley has recently been using a solution 

 of ammonium nitrate and finds it dissolves at least as much potas- 

 sium, calcium, etc., as an acid, and in some respects is more satis- 

 factory. This method of extracting the bases from soils was devised 

 by Prof. Ramann, under whom Mr. Hanley worked for a time. 



These investigations promise to clear up many of the difficulties 

 in soil analysis. 



THE PLANT NUTRITION WORK. 



The fundamental problem in plant nutrition is the production 

 of sugar in the green leaf, but the investigation is seriously hampered 

 by analytical difficulties. During the past three years considerable 

 improvements in method have been effected by Mr. Davis and his 

 assistants, Messrs. Daish and Sawyer, and this year satisfactory 

 proof has been adduced of the presence of free pentoses in the leaf 

 and a method has been elaborated for determining them. 



The complete method now allows of the determination of cane 

 sugar, maltose, dextrose, levulose, pentoses, starch, and pentosans in 

 the leaf. It has been used for numerous analyses of leaves and 

 stalks plucked at regular intervals during the day and night, the 

 results of which will be discussed later. 



Equally important from the standpoint of crop production is the 

 formation of starch in the grain. Analytical difficulties have hitherto 

 prevented a satisfactory investigation, but this year the determina- 

 tion of starch has been put on a satisfactory basis. The existing 

 methods may give rise to an error equal to 20 per cent, or more 

 of the starch present : in the ordinary diastase method, for example, 

 a loss of this magnitude may arise from the precipitation of dextrin 

 during the preliminary processes of precipitation. A new method 

 has therefore been devised, based on the fact that the enyzme taka- 

 diastase transforms starch quantitatively into maltose and dextrose, 

 no dextrin being formed : thus the errors of the ordinary method are 

 obviated. This is apparently the only trustworthy way of esti- 

 mating starch in plant tissues, and it is now being used for wheat 

 and barley grown on the Rothamsted plots. 



During the year Dr. Brenchley has been engaged on an 

 extended survey of the grass plots ; a complete botanical analysis is 

 being made, and the results are compared with the last survey of 

 1903 and the earlier ones of 1862, 1867, 1872 and 1877 in order to 

 follow the change brought about in the herbage. A survey of the 

 weed flora of certain of the fields, and of the flora of Geescroft and 

 the Wilderness, has also been made and compared with that of 

 earlier years. All these results are being worked up both from the 

 agricultural and the ecological standpoints. 



The investigations on the effect of certain organic substances 

 on plant growth have been continued, and progress has been made 

 by Miss Adam with the study of the effect of potassic manuring on 

 the anatomical structure of a grass {Dactylis glomerata). 



At the present time eleven of the laboratory staff and research 



