January 7, 1921] 



SCIENCE 



was not an experimenter and cared little for 

 it. In Germany, under his influence taxonomy 

 d^enerated into mere plant collections, col- 

 lectors calling themselves tasonomists. 



POST-LINN^AN BOTANY 



A new era opened with such men as Jussieu, 

 Gaertner, DeCandolle, Eobert Brown, Adan- 

 son, Endlicher who knew how to observe and 

 interpret the things they saw. Experimental 

 work with plants became more important ; bot- 

 anists began to ask the why about plants ; and 

 so E. Mariette, one of the first experimental 

 physicists, studied the salts of plants and the 

 active forces of attraction and nutrition. 



Martin Lister directed attention to the 

 movement of water in plants. Christian 

 Wolff, too, experimented on the nutrition of 

 plants. Stephen Hales in his " Statistical Es- 

 says " sought to trace back the phenomena of 

 vegetation to mechanico-physical laws, as then 

 ujiderstood, and studied the water taken in by 

 plants and its exit by the leaves and the for- 

 mation of solid substances. 



The discovery of oxygen by Priestley was 

 important in plant physiology, but he missed 

 the important discovery that light is a vital 

 factor in making plant food. This was left to 

 Jean Ingenhousz, whose experiments showed 

 that purifying of air goes on in light only. 

 This led him to study the food of plants and 

 the improvement of soils. He discovered that 

 plants use CO2 and under the influence of 

 light make plant food. Jean Senebier was the 

 first to give a clear statement of the process 

 of photosynthesis. We are indebted to the 

 chemist, DeSaussure, for his discoveries, which 

 laid the foundation in an experimental way of 

 the process of food-making in plants. It is a 

 long way from the researches of these pioneers 

 to the work of Boussingault's quantitative 

 methods of studying the food requirements of 

 plants, especially with reference to nitrogen, 

 and the work of Sprengel on ash constituents 

 and Liebig's work, " Chemistry in its Relation 

 to Agriculture and Physiology." These greatly 

 helped to advance plant physiology, as did 

 also the work of Lawes and Gilbert on the 

 mineral constituents of plants and later the 



pot culture method of Knop, Sachs, and the 

 work of Lachmann, who in 1858, spoke of the 

 " Vibrionenartige " organisms found in legu- 

 minous nodules. Later the work of Schloes- 

 ing and Muntz, Warrington, Beijerinek, Wino- 

 gradsky, Hellriegel and Wilfarth and many 

 others made secure for ever a better agricul- 

 tural practise. Added to the knowledge of 

 the importance of the legume bacteria the im- 

 portant discoveries of Wollny and Berthelot 

 show that bacteria in the soil are the makers 

 of plant food. 



Plant physiological work in Europe made 

 rapid strides through the labors of Detmer, 

 Pfeffer, Sachs, Jost, Palladin, Haberlandt and 

 many others. The question of photosynthesis 

 long remained obscure because of insufficient 

 chemical study of the plant pigments. The 

 environmental factors were partially deter- 

 mined by F. B. Blackman and then Willstatter 

 and his coworkers determined the chemistry of 

 chlorophyll, which enabled plant physiologists 

 to better understand the problems of carbon 

 assimilation. Jorgensen and Walter Stiles in 

 their resume say: 



No prophetic vision is needed to foretell devel- 

 opment in plant physiology as great as those which 

 were produced by physics and chemistry in engi- 

 neering and other technical sciences. 



It is refreshing to observe that a soil physi- 

 cist like Edward Russell in his paper " Soil 

 Conditions and Plant Growth," should put 

 stress on plant physiological problems as 

 fundamental to a study of soils and plant nu- 

 trition. 



Jung did not entertain any definite idea of 

 the sexuality of plants nor did Grew have a 

 clear conception. Rudolph Camerarius, how- 

 ever, settled the problem by making experi- 

 ments with maize and mulberry, two economic 

 plants. 



We can only marvel at the economic trend 

 of the work of Leewenhoek in the study of 

 linen, who made the discovery of minute or- 

 ganisms, and thus repudiated the theory of 

 abiogenesis. People became curious to study 

 the hitherto unseen world. The use of the 

 microscope in the hands of the curious was 



