278 



THE POPULAR SCIENCE MONTHLY. 



the old editions, structural and physiologi- | 

 cal botany were considered together. There 

 was no attempt to deal with them separate- 

 ly. But the present volume is specially de- 

 voted to structural botany, and leaves out 

 physiology as far as possible. This diifer- 

 ence is really greater than at first appears. 

 Although structural botany was given along 

 with physiology in the old editions, yet phys- 

 iology was the only division of the science 

 that was really learned from its pages. Of 

 course, this was not intended by the au- 

 thor ; but, with the human mind what it 

 is, and the public schools such as they are, 

 no other result was possible. When this 

 work first appeared, and for long years 

 thereafter, studying objects was undreamed 

 of in our schools; lesson-learning ^was their 

 sole occupation. But a descriptive science 

 can not be learned from the pages of a 

 book. Physiology could be acquired by 

 the prevailing method, since it takes little 

 account of the differences among plants, 

 and would be much the same if the vege- 

 table world consisted of only one species. 

 The impression made upon pupils by the 

 descriptive portions of " Gray's Class-Book " 

 was so slight that, to the average student, 

 the science of botany and the physiology of 

 plants were about the same thing. 



And so it happened that class after class 

 of our youth left school complacently think- 

 ing that they knew botany, but with only 

 the merest book-smattering concerning the 

 classification of plants. Of course, if the 

 forms and modifications of the organs of 

 plants were not regarded, there could be 

 little occasion for glossology ; and, by the 

 neglect of both organography and glossolo- 

 gy, the sketch of the natural orders at the 

 end of the volume was unintelligible. This 

 could only be understood when the actual 

 features of a large variety of plants were 

 familiar to the mind, and the memory was 

 also furnished with the exact terms applied 

 to them. Educationally considered, there- 

 fore, this chapter of illustrations of the nat- 

 ural orders, covering more than a hundred 

 pages, was little better than waste-paper. 



The order of publication now adopted, 

 which presents structural botany by itself 

 at the outset of the study, will compel the 

 teachers of botany to change their practice, 

 and make the study of plants by direct ob- 



servation a serious business. For, interest- 

 ing and fundamental as is the physiology 

 of plants, the discoveries of the last twen- 

 ty years have rendered their morphological 

 study more captivating still, so that the in- 

 terest of the science reaches its highest 

 point in systematic botany, or classification 

 on the basis of genetic relationship. But 

 the only possible admission to this delight- 

 ful portion of the subject is through such a 

 genuine knowledge of the contents of the 

 present work as will come from wide and 

 careful observation of living vegetable forms. 

 Another noticeable change in this treat- 

 ise is the substitution of the doctrine of the 

 development of species by natural selection 

 for that of the special creation of species, 

 which was taught in all former editions. 

 The fifth was published in ISSY, and Dar- 

 win's work on the " Origin of Species " did 

 not appear until 1859. The new direction 

 given to inquiry in natural history by this 

 work, and the copious literature of the sub- 

 ject which followed it, have profoundly al- 

 tered the aspects of biological science. The 

 old system of comparative anatomy, which 

 was based upon the doctrine of special cre- 

 ations, has given place to the modern sci- 

 ence of morphology ; which, from being, 

 before Darwin's time, merely a descriptive 

 study of forms, has become an analytical 

 science of form, pervaded throughout by the 

 principle of descent with variation. The 

 following extract from his chapter on "The 

 Principles of Classification " will sufficiently 

 indicate the present attitude of Professor 

 Gray toward the question of the evolution 

 of species : 



The theory of descent, that is, of the diversi- 

 fication of the species of a geuus through varia- 

 tion in the lapse of time, aftbrds the only nat- 

 ural explanation of their likeness which has yet 

 been conceived. The alternative supposition, 

 that all the existing species and forms were 

 originally created as they are, and have come 

 down essentially unchanged from the beg^inning, 

 offers no explanation of the likeness, and even 

 assumes that there is no scientific explanation 

 of it. The hypothesis that the species of a ge- 

 nus have become what they are by diversifica- 

 tion through variation is a very old one in bot- 

 any, and has from time to time been put for- 

 ward. But, until recently, it has had little in- 

 fluence upon the science, because no clear idea 

 had been formed of any natural process which 

 I might lead to such result. Doubtless, if varia- 

 I tion, such as botanists have to recognize within 



