2i6 HISTORY OF BOTANY 



was clearly seen to be in the form of starch grains, other 

 carbohydrates were recorded as replacing starch, e.g. 

 glycogen, inuUn, and even cane-sugar. 



Our knowledge was by no means so extensive as to 

 the nitrogenous reserves, although one of these, viz. 

 aleurone, had been the subject of enquiry by Hartig 

 as far back as 1855. Such work as was accomplished 

 was carried out chiefly on seeds, first by Hoppe-Seyler, 

 and later by Vines and two American investigators, 

 Chittenden and Osborne. 



Sachs, in his early researches on the carbohydrates 

 of the leaf, had noticed the occurrence of oil as a reserve, 

 and studied its origin and fate. In spite of the chemical 

 difficulties involved, he held that fats might arise from 

 carbohydrates, and carbohydrates from fats. Naegeli 

 and others, some years later, regarded the fats as direct 

 products of the protoplasm, while Wakker and Zimmer- 

 mann, towards the end of the century, determined the 

 existence of bodies to which the name of elaioplasts was 

 given, whose duty it was to secrete oil drops. 



Other organic substances, such as glucosides, were 

 also identified in plants towards the end of the century, 

 and believed by many authorities to be of the nature of 

 reserves. 



Enzymes 



As we have already seen, all reserve bodies had to be 

 transformed from the resting, usually insoluble, condition 

 into a soluble state before they could be transported 

 from the seats of storage to the regions where they were 

 required as constructive plasta, and to effect this trans- 

 formation certain agents were necessary ; these agents, 

 as you know, are enzymes. 



The first enzyme to be identified was diastase, which, 

 as I have already stated, was obtained in 1833, by 

 Payen and Persoz, from germinating barley. After the 

 middle of the century, investigator after investigator 



