74 



SYSTEMATIC BOTANY 



new instruments and techniques which 

 enlarge tlie field and scope of his per- 

 ceptions. 



In the beginnings of herbarium 

 practice it was tliought that a single 

 specimen was sufficient to represent a 

 species or kind of plant. This, I think, 

 can be linked directly with the Doc- 

 trine of Special Creation, a philosophy 

 then current which held that, being 

 specially created, all plants of a given 

 kind must look alike. Therefore, in 

 those early days, it was thought no 

 more necessary to clutter up an her- 

 barium with "duplicate" specimens of 

 a kind of plant than to burden a private 

 libran- with duplicate copies of the same 

 book. But if man's philosophy in eon- 

 junction with his passion for classifica- 

 tion, led him to set up a scries of defi- 

 nitions bounding these classificatory 

 units, these kinds or species of plants, 

 it was his insatiable curiosity which 

 drove him to determine the modulus 

 of variation permissible within them. 

 ^But botanists soon discovered that 

 words were not a completely satisfac- 

 tory medium for the recording of these 

 variations, that a concrete object was 

 in all ways better, for words, no matter 

 how they are used, are often inadequate 

 to express those differences which hu- 

 man perception indicates are present. 

 And thus began the current herbarium 

 practice of having more than one rep- 

 resentative specimen of each kind of 

 plant. 



But there soon came a time when 

 this curiosity led the botanist into a 

 series of difficulties, for he began to 

 find his former units of classification 

 unwieldy and was faced with the prob- 

 lem of setting up new units bounded 

 by more finely drawn distinctions. It 

 was then that he fully realized the 

 necessity of having easily available at 

 all times a wide assortment of speci- 

 mens—records of the plants as they are 

 found in nature— for onlv thus can he 



arrive at any reasonable conclusion as 

 to where to draw the lines indicative 

 of the limits of variation between his 

 several entities. 



I have spoken of new instruments 

 and techniques which enlarge the field 

 and scope of man's perception. Among i 

 these we need to mention only one, the 

 microscope. Here is a machine which 

 permits the user to see clearly that 

 which his unaided eye alone could not 

 discern. But the microscope is not 

 solely an instrument of visual percep- 

 tion. It is a tool and, in the hands of 

 the trained worker, ceases merely to be 

 a machine whereby the invisible is 

 made visible but, probing deeply into 

 the recesses of our ignorance, becomes 

 a tester of conclusions derived from the 

 observation of objects in the gross, a 

 dissector of biological h}pothcses and 

 thus, out of the fragments of our pre- 

 conceived notions, an instrument for 

 the building of new and better taxo- 

 nomic concepts. 



In the past the taxonomist, the 

 namer of plants, was not immediately 

 concerned with the mechanics of evo- 

 lution. Lately he has come to realize 

 that these apparently minor variations 

 with which he has been dealing are of 

 more than casual significance, being 

 the loose ends of threads in the tan- 

 gled and often knotted skein of evolu- 

 tion, and to understand them is to un- 

 derstand evolution itself. Hence the 

 needs of the taxonomist for as many 

 examples of these variations as possible 

 —herbarium specimens representative 

 of the sum total of the differentiations 

 of plants— for only bv a study of these 

 can he hope to reach anv conclusion 

 as to the directions which evolution has 

 taken within the group under con- 

 sideration. Knowing this, he then can 

 draw the lines between his units of 

 classification— his genera and species- 

 in a reasonably satisfactory manner. 



As this is read, there are in this her- 



