Vol. XXII. No. 4.] 



POPULAR SCIEITOE NEWS. 



51 



a laboratory adapted from the garden tool-house, 

 and in reading with care several books on the sub- 

 ject. " This," he says, '• was the best part of my 

 education at school, for it showed me practically 

 the meaning of experimental science." 



During his two years in the medical school of 

 Edinburgh University, Darwin made the acquaint- 

 ance of several young men fond of natural science, 

 and contributed to a natural-history club among 

 the students one or two interesting little zoological 

 discoveries made while dissecting, without any 

 regular training, and with a " wretched microscope," 

 specimens found in the tidal pools or dredged from 

 the sea. From one of his friends he heard enthu- 

 siastic eulogy of Lamarck and his theory of evolu- 

 tion, which derived all the plants and animals now 

 living, including man himself, from pre-existing 

 simpler forms, by a process of slow and gradual 

 modification of structure and instinct produced by 

 the effort of the individual to adapt itself to a 

 change in the conditions of its life. Darwin had 

 previously read similar views in the Zoonomia of 

 his grandfather, Erasmus Darwin ; and though he 

 paid little attention to them at this time, he 

 thought long afterwards that the hearing of them 

 maintained and praised early in life may have fa- 

 vored his upholding them under a different form 

 in the Origin of Species. 



The careful study of the works of Paley, the 

 public botanical lectures of Professor Henslow, 

 field excursions with the botanists of the Univer- 

 sity, and collecting beetles with eager entomolo- 

 gists, were among the educational influences of 

 Darwin's three years at Cambridge. Of these the 

 most potent in its after-effects was the friendship 

 formed with Professor Henslow, a man of well- 

 balanced mind, great knowledge of the natural 

 sciences, and a strong taste for drawing conclusions 

 from long-continued minute observations. At the 

 house of Professor Henslow, Darwin met many of 

 the most distinguished men of the University, 

 whose varied and brilliant conversation stimulated 

 his mental activity and ambition. These were, 

 moreover, nourished by the careful reading of 

 Humboldt's Personal NarraUoe and Sir J. Her- 

 schel's Introduction to the Study of Natural Phi- 

 losophy, " which books," he says, stirred in him 

 "a burning zeal to add even the most humble 

 contribution to the noble structure of natural 

 science." 



Up to the time of his leaving Cambridge, in 1831, 

 science had been to Darwin but one of the many 

 recreations of a happy, careless life, contributing 

 but indirectly to the education of his mind. His 

 first real scientific training was gained when, as 

 Naturalist to the Beagle, he was forced to attend 

 closely to several branches of natural history, to 

 bring into play powers of reasoning as well as of 

 observation, and to make every thing about which 

 he " thought or read bear directly on what he had 

 seen or was likely to see." 



In the early part of the voyage he read with 

 care the first volume of Lyell's recently published 

 Principles of Geology, in which a great mass of 

 facts was brought forward to support the principle 

 that the changes in the past geography of the globe 

 were wrought by the same forces which we see at 

 work in the present, — a principle which, though 

 subversive of all the "world-wide catastrophes" 

 dear to the geologists of Ihe period, was recognized 

 to be true by Darwin as soon as an opportunity 

 came to put it to the test. 



World-wide catastrophe having been eliminated 

 from the history of the earth, there remains no 

 cause for the sudden extinction of one set of or- 

 ganic forms and the substitution of another by 

 special creation. Lyell was quite aware of this; 

 but so long as the gradual derivation of one species 



from another remained a mere logical deduction, 

 with no better support than a suggestion from the 

 brain of the gifted Lamarck, he, like other scien- 

 tific men at tha;t time, hesitated to express himself 

 positively on the subject. 



Having grasped the principle of uniformity, 

 Darwin could not but see that consistency de- 

 manded its application to the whole realm of 

 nature, organic as well as ino;-ganic. His belief 

 in the theory of special creation was shaken, and 

 before the end of the voyage it was destroyed for- 

 ever by finding in South America fossil remains 

 of gigantic armor-clad animals allied to existing 

 armadillos of the same continent. Being also 

 much impressed by the resemblance between the 

 productions of the Galapagos Archipelago and 

 those of South America, and the differing slightly 

 of those productions from island to island, it be- 

 came evident to him that these and many similar 

 facts could be explained only by a gradual modifi- 

 cation of species. At the same time, it seemed to 

 him that changes in surrounding conditions, such 

 as climate, food, etc., could not alone account for 

 all the adaptations of organisms to their mode of 

 life, and that Lamarck's addition of effort on the 

 part of the organism was inapplicable in the case 

 of plants. The subject, he says, haunted him; and 

 shortly after his return to England he determined 

 to follow Lyell's example in geology, and collect 

 from the whole organic kingdom, and on a whole- 

 sale scale, all facts bearing in any way on the que.s- 

 tion of species. 



As it seemed to Darwin that light might be thrown 

 on the problem by a careful study of domesticated 

 animals and cultivated plants, he sent out printed 

 inquiries whenever information promised to be 

 forthcoming, plied his friends with questions, con- 

 versed with skilful gardeners and breeders, and 

 read and "abstracted" an immense number of 

 books, journals, and transactions. He soon per- 

 ceived, he says, that selection was the keystone of 

 man's success in making useful races of animals 

 and plants: but how selection could be applied to 

 organisms living in a state of nature, was inexpli- 

 cable to him until, in October, 1838, happening to 

 read for amusement Matthus on Population, ;md 

 being well prepared to appreciate, from long-con- 

 tinued observation of the habits of animals and 

 plants, the struggle for existence which everywhere 

 goes on, it at once struck him that under these 

 circumstances favorable variations would tend to 

 be preserved, and unfavorable ones to be destroyed ; 

 and the result of this process continued through 

 untold time would be the formation of species. 

 " Here, then," he says, "I had got a theory by 

 which to work." 



But so anxious was Darwin to keep his mind 

 free from prejudice at this early stage of his in- 

 quiry, that it was not till the summer of 1842 that 

 he allowed himself to write even the shortest 

 sketch of his theory. This sketch, somewhat en- 

 larged in 1844, was again set aside until, having 

 tested his hypothesis by nature, thought, extended 

 observations, and abundant experiment, he should 

 feel justified in offering to other scientific workers 

 "natural selection" acting through the "strug- 

 gle for existence " as the basis of organic evolu- 

 tion. This caution and self-restraint were not 

 without reward; for when at last, in 1859, Darwin 

 gave his results to the world, no critic, however 

 hostile, was able to bring forward a single objec- 

 tion that had not already been considered, while 

 the clear reasoning and striking illustrations with 

 which his views were presented had no small share 

 in producing that change in the aspect of biological 

 science which is one of the wonders of the nine- 

 teenth century, and the direct and necessary out- 

 come of the Origin of Species. 



[Original in Popular Science 2fewa.] 

 BOTANY AS A RECREATION. 



BY FREDERICK LEROY SARGENT. 



IV. 



PHYSIOLOGICAL BOTANY. 



In the study of plants from a physiological 

 stand-point, the main endeavor is, to discover how 

 they live, the details of their structure, and the 

 uses or significance of their several parts. The 

 various questions which are thus involved must 

 be answered by different means, — sometimes by 

 performing experiments, and sometimes by study- 

 ing form or construction. 



For the encouragement of those who would 

 rather study plant-life than plant-names, it may 

 be said that such a general acquaintance as most 

 persons possess of the common names of common 

 plants is quite sufficient for the needs of a be- 

 ginner in physiological botany. Proficiency in 

 systematic botany is, of course, very helpful in the 

 study of plant-life, and in most of the books to 

 which we shall refer, the student will find that a 

 knowledge of names is constantly presumed ; still, 

 the knowledge called for is mostly of a kind that, 

 when needed, can usually be easily obtained by 

 reference to a dictionary or to a general systematic 

 work. 



The principle of verification, which we have 

 already advocated in systematic botany, is especial- 

 ly valuable for a beginner in physiological studies. 

 At the outset, the most profitable as well as the 

 most enjoyable manner of working is to read some 

 good book, and attempt to see for one's self, as 

 as much as possible, of what is spoken of, — re- 

 peating the experiments described, and hunting 

 up examples of the structures that are mentioned. 

 A most fertile source of pleasure is, however, neg- 

 lected if the student does not extend his investi- 

 gation bej'ond mere verification. Books can at 

 best tell only what has been already learned on 

 a given question ; and to an intelligent student 

 there will be suggested interesting ways in which 

 this knowledge may be extended, and thus he will 

 be led to supplement his verification studies by 

 the delights of independent work. 



In the study of animals, it has long been under- 

 stood that the various organs of their bodies are 

 adapted, often in a most beautiful way, by their 

 form and other qualities, to fulfil those offices 

 which the welfare of the animal requires. Thus, 

 in our conception of a bird there enters an idea 

 of the wonderful mechanism of fiight; the ways in 

 which lightness and strength are secured in the 

 skeleton ; the form of the feet as adapted for 

 perching or wading or swimming, as the case may 

 be; the shape of the bill, as fitting it for a special 

 use ; and a number of other adaptations of means 

 to ends by which the creature is fitted to the con- 

 ditions under which it lives. In plants it has been 

 only within comparatively recent times that adap- 

 tations to environment have been recognized; but 

 to-day such considerations hold a prominent place 

 in the minds of botanists, and offer one of the 

 most attractive fields upon which a student can 

 enter. 



For the most part, there is no need of other than 

 the simplest apparatus ; and for much of the work, 

 none at all is required. In the matter of books, 

 the student in this field is especially fortunate, for 

 it would be hard to find more delightful scientific 

 literature than has appeared of late years in this 

 department. 



As particularly useful for beginners, we can 

 recommend Gray's How Plants Behave, a charm- 

 ing little book, written for young people, but 

 fully worthy of older readers; and Lubbock's 

 Flowers, Fruits, and Leaves, and British Wild 



