556 History of the Doctrine of [BOOK in. 



firmer foundation for future theory. But no conclusive results, 

 no such entirely new points of view were gained before 1860, 

 as were established during the same time in phytotomy, mor- 

 phology, and systematic botany. To these subjects the most 

 eminent enquirers applied their best powers almost exclusively, 

 while phytodynamics vanished from the field of view of the 

 generality of botanists, and no one made them the object of 

 the comprehensive, intense, and effectual study, which Dutro- 

 chet had previously devoted to them. At the same time his 

 example was not without a powerful effect. The working of 

 endosmose was further investigated and treated as a part of 

 molecular physics. Greater freedom was thus gained in the 

 mechanical treatment of phytodynamical questions, and a firmer 

 basis secured by aid of the advances which were being at the 

 same time made in phytotomy. But with the exception of 

 Briicke's essay on Mimosa (1848), the works produced during 

 this period were chiefly devoted to the critical examination of 

 the writings of previous observers, and whatever appeared that 

 was new and positive remained incomplete till after the date at 

 which this history ends. Under these circumstances we must 

 be content to indicate briefly the more important of the new 

 discoveries and of the efforts made at this time to advance the 

 theory of the subject. 



Several observers occupied themselves soon after 1840 with 

 the influence of light on the growing parts of plants. Payer 

 maintained in 1843 that the radicles of various Phanerogams 

 turn from the light, and a controversy arose between him and 

 Dutrochet on the point, in which Durand took part in 1845, 

 but no definite conclusion was arrived at even as regards the 

 certainty of the fact. The beautiful discovery of Schmitz in 1 843, 

 that the Rhizomorphs grow more slowly in the light than in the 

 dark, and are at the same time negatively heliotropic, might 

 have proved much more important ; but the theoretical value 

 of this fact has till quite recently been entirely misconstrued. 

 Sebastian Poggioli had discovered in 1817 that highly refringent 



