280 The Physiology of Plants BOOK in 



struction of organic substance so far on the way to com- 

 pleteness. 



It is to the work of Sachs himself that we are indebted 

 for the establishment of no inconsiderable part of the 

 foundation on which our modern views are resting to-day. 

 He called attention to the part played by chlorophyll ; 

 he correlated the growth and nutrition of the organs of 

 the plant with the activity of the chlorophyll corpuscles ; 

 he investigated the conditions of the formation of the pig- 

 ment, and showed its relation to light and its dependence 

 thereon for both its formation and its subsequent activity ; 

 and he for the first time demonstrated what are at any 

 rate some of the products of its activity. 



But this is not all the credit that must be rendered to 

 Sachs in the solution of these great problems. By his 

 own illuminating researches he opened the way to the work 

 of others, work very largely carried out under his own 

 inspiration by his many famous pupils. The light he threw 

 upon these questions stimulated enthusiasm in many other 

 quarters than Wiirzburg, and a great outbreak of research 

 into the chemical and physical problems connected with 

 life became noticeable throughout all Europe. 



While Sachs' researches were carried out with great care 

 and exactness for the time, it is not surprising that many 

 of his conclusions, though fundamentally sound, have been 

 found to need considerable modification in later years, as 

 the resources of chemistry and physics have developed and 

 the older, somewhat crude methods of research have given 

 place to others which admit of more exactitude. That was 

 only to be expected and cannot detract from the merit of 

 Sachs' achievements. 



The study of the nutritive processes of plants, starting 

 again then from the school of Sachs, has been directed to 

 four main points in connexion with the formation of carbo- 

 hydrate substance. These have been the gaseous inter- 



