430 RELATION OF PLANT PHYSIOLOGY TO OTHER SCIENCES. 



Ill liis epoch-making Elements of Systematic Botany, Schleideu, near 

 the middle of the century, challenged the systematists in these words: 

 "The time has passed wherein a man who could give the names of 6,000 

 plants would because of that be called a botanist, but another who knew 

 10,000 plants would be designated a greater botanist, and the formerly 

 so-called systematic botany has been thrust back into its proper place 

 of simply a hand servant of the true and exact sciences." But the sys- 

 tematists returned the thrust. One of her foremost representatives 

 declared to the men of the " true science:" " If one were to collect all 

 the positive results thus far offered by plant physiologists it would 

 scarcely suffice to till a nutshell." Wrong judgments lay here on both 

 sides, such as are always called forth by insufficient knowledge and 

 limited insight into the relation of things. The principle of the division 

 of labor led here, as usual, first to a separation of two so closely related 

 territories, and it was only as one of the later results of the applica- 

 tion of this principle that they were again brought into their natural 

 relations. 



The science, however, incurred no lasting injury from the fact that 

 descriptive botany and physiology first pursued opposite ways. In 

 each field good constructive material was accumulated. An earlier 

 commencement of common constructive work would only have led to 

 complications. 



A really gratifying prospect is presented when one considers how 

 gradually systematic botany was advanced by this branch of physiology 

 in its widest sense. Linnaeus and his school could still content them- 

 selves with a very elementary form of plant description, form and 

 position of leaves, number and arrangement of flower parts — in short, 

 any character which a plant in flower presented to the naked eye suf- 

 ficed for the end of plant description as then pursued. Now, however, 

 a hundred thousand species of plants are known. Of orchids alone 

 there are as many species as all the species of plants described by Lin 

 nseus put together, and it is easy to see how the few superficial charac- 

 ters at first used for distinction of species became wholly inadequate. 

 Besides, descriptive botany could not content itself with simply distin- 

 guishing plant species and supplying them names. 



Furthermore, it became necessary to consider the systematic arrange- 

 ment of the ever-increasing species. There had also to come into play 

 that great principle of natural science investigation which one of our 

 most distinguished colleagues has called the ''economy of science." 

 When I speak of orchids 1 express the sum of all those characters 

 which are common to these 8,000 species. This expression of the sum 

 of common characters must possess this quality, that by it I can dis- 

 tinguish this plant group from all others and, besides, express their 

 relationship to other groups. The sum total of isolated characteristics 

 must be brought into the simplest, briefest expression possible. Lin- 

 naeus sought to attain this "economy" by his artificial system. This 



