JULIUS SACHS. 165 



fundamental importance of which needs hardly to be demon- 

 strated at the present day. 



The formation of starch largely engaged his attention 

 later on. He contrived a simple means of quantitatively 

 estimating- starch-assimilation, and by the application of the 

 " iodine test " to leaves or portions of leaves respectively, 

 supplied an extraordinarily simple and instructive method 

 of demonstration. 



His services in improving the culture of plants in 

 nutrient solutions are well known. They drew down upon 

 him a violent attack from Knop which deeply wounded 

 him, and not without reason. It is now one of the most 

 elementary experiments in the physiology of plants to rear 

 a plant from germination to seed-bearing by the adminis- 

 tration of nutrient salts ; but at that time it was maintained 

 that the seed-bearing plants of maize must have been placed 

 in the solution of nutrient salts after they had attained a 

 flourishing condition ! 



He incidentally discovered the interesting fact that 

 polished marble slabs may be corroded by roots ; a fact of 

 some importance for the understanding of the functions of 

 these organs. He began to work upon entirely virgin soil 

 when, at the close of his fiftieth year, he set on foot investi- 

 gations which brought to light by microscopical tests, and 

 above all by microchemical methods, the movements, 

 chemical changes, and final consumption of the reserve 

 material during the growth of organs. These experiments 

 have also proved of fundamental importance, and he lays 

 stress upon the fact that they served to first lead him to 

 think that the chlorophyll grains are the true organs of 

 assimilation. A bare reference must suffice to the classical 

 treatises on the germination of the date-palm, of grasses, 

 or on inulin, etc. 



In later years he ceased to contribute experimentally to 

 our knowledge of metabolism. Other problems had mean- 

 while claimed his attention. His investigations — the first to 

 be made — into the action of heat claim special notice. The 

 phenomena of freezing had long been in need of investiga- 

 tion, and here also Sachs' work created a clear conception 



