XXV 



zoological (on the Crajfish and on Dinotherium (jigardeum) and one 

 botanical (" Ueb. das Wachsthum der Pfl.au zen "), followed by a 

 series of botanical papers, mostly morphological and systematic, 

 which appeared in the same journal in the course of the years 

 1854-56. During this period two papers of his appeared in the 

 ' Botanische Zeitung ' (1855) on Gollema and Orucibulum respectively ; 

 the former of these is of special interest inasmuch as in it Sachs 

 expresses views which nearly anticipated the theory of the structure 

 of Lichens propounded by Schwendener in 1868, and now almost 

 universally accepted. But it is not until 1857 that we find him 

 devoting himself especially to that department of botany with which 

 his name will always be associated, when he commenced that series 

 of physiological investigations which he carried on, with scarcely an 

 interval, for more than a quarter of a century. The most important 

 line of research which he struck out in what we may term his 

 Prague- period, was that of investigating the metabolism of the plant 

 by means of the rnicro-chemical examination of the tissues. Begin- 

 ning with the paper " Ueb. einige neue microscopisch-chemische 

 Reactions-methoden,"* it led on to the series of " Keimungsgeschich- 

 ten," relating to a variety of plants (bean, grasses, date, onion, &c), 

 the publication of which extended over a number of years, and which 

 may be fairly said to have laid the foundation of our knowledge of 

 micro- chemical methods, as also of both the morphological and 

 physiological details of the process of germination. 



The period of his tenure of office at Tharandt is memorable for 

 his resuscitation of the method of " water-culture," originally sug- 

 gested by Duhamel,f and the application of it to the investigation 

 of the fundamental problems of nutrition. It is to the introduction 

 of this method that we owe whatever accurate knowledge we possess 

 of the relative physiological importance of the various mineral con- 

 stituents of the plant's food. 



Of the many valuable contributions to plant-physiology which 

 Sachs made whilst at Poppelsdorf (1S61-67), perhaps the most 

 fundamentally important are those which relate to the function of 

 chlorophyll. Whilst Von Mohl and others had recognised the almost 

 universal occurrence of starch-grains in the chloroplastids, it remained 

 for Sachs to give the explanation of the fact. He ascertained that 

 the formation of starch-grains in chloroplastids is dependent upon 

 exposure to light ; in other words, upon the conditions already known 

 to be essential for the absorption and decomposition of carbon 

 dioxide by the green parts of plants. Bringing these facts into their 

 proper correlation, he arrived at the weighty conclusion that the 



* ' Sitzbcr. d. k. Akad. d. Wiss. in Wicn,' vol. 26, 1858. 

 f ''Physique des Arbrcs,' 1753. 



