374 The Physiology of Plants BOOK in 



stated by Sachs. We have seen that he himself con- 

 tributed not a little to the solution of the first the question 

 of the process of construction of carbohydrates. In con- 

 nexion with his researches on this point he made many 

 equally valuable observations on the second of the problems. 

 In 1864 he found evidence of the migration of the first- 

 formed starch from the leaves, in that while a leaf may 

 contain a very large amount at night, very little may 

 remain in it in the early morning. The idea of a nocturnal 

 migration following a daylight formation was at once sug- 

 gested, but further experiments led him to see that the 

 starch is removed in light as well as in darkness, though 

 the observation can be made only with greater difficulty 

 in consequence of the coincident constructive processes. 

 Further light was thrown upon the question of trans- 

 location in 1873, when Godlewski and Pfeffer independently 

 proved that starch disappears from a leaf when it is kept 

 for a long time in an atmosphere devoid of carbon dioxide. 

 This observation was repeated by Morgen in 1877. These 

 researches, taken together with those of Sachs, prove that 

 migration of carbohydrate goes on continuously and can 

 be observed readily as soon as its formation stops. Sachs 

 made no statement as to the form in which the starch 

 travels until, in his Vorlesungen, in 1882, he said he was 

 inclined to assume it to be some form of sugar. 



The relations between starch and sugar had been investi- 

 gated much earlier. As far back as 1814 Kirchoff had found 

 that germinating barley grains yield to extraction by water 

 something that is capable of converting the former into 

 the latter, and other writers had incidentally noticed the 

 same thing in connexion with similar researches. This 

 substance, which later came to be recognized as diastase, 

 was not especially studied after Sachs' experiments till 

 1874, when its examination was resumed by Gorup-Besanez. 

 Its relation to the migration of starch from leaves was 



