42 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



These reduction methods were checked by fermentation 

 with yeast, when it was found that no substances optically 

 active remained in the solutions. The error arising from 

 the slight cupric reducing -power of sucrose in presence of 

 hexoses was avoided by first estimating the sucrose from 

 the loss of rotation through hydrolysis. 



THE METHODS OF THE ROTHAMSTED EXPERIMENTAL 



STATION. 

 Since the researches of Strakosch (1907) and Mangham 



(1911) were almost entirely microchemical and qualitative, 

 the next reasearch requiring mention is that on Beta 

 maritima, the mangold. This was begun by Campbell 



(1912) and continued by Davis and Daish (1913, 1914). 

 Campbell found that drying at 100, or killing with 



chloroform, ether, or toluene, before drying, greatly influ- 

 enced the sugar content. The plan finally adopted was 

 to immerse the chopped-up leaves in boiling alcohol, after 

 removal of the midrib, and to begin the extraction at once. 

 The percentage of dry matter was determined in another 

 portion. Extraction was continued till all colouring 

 matter was removed from the leaves, as it was found that 

 this corresponded to complete extraction of the sugars. 

 The solution was then concentrated with removal of the 

 alcohol, and estimated by Pavy's solution, after clarify- 

 ing by heating for a few seconds with alumina cream or 

 kieselguhr and filtering. Inversion of sucrose was effected 

 by boiling for seven minutes with 2 per cent, citric acid, 

 and that of maltose by further hydrolysis of a diluted 

 portion with 10 c.c. of concentrated hydrochloric acid for 

 an hour. The results so obtained are admittedly not 

 absolute, but it is claimed that they are comparable. The 

 starch was estimated by 'Sullivan's diastase method after 

 gelatinization. It must be noted that all these de tormina- 



