534 



NA TURE 



[September 28, 189; 



by the Photographs Committee, of which, however, onlya small 

 selection could be shown, those exhibited by the Scottish Geo- 

 logical Survey, and the specimen slides and maps to illustrate 

 papers and discussions, kindly lent by Prof. Sollas, Messrs. 

 Teall, Topley, Johnston Lavis, Gregory, and many otheri. This 

 exhibition, if it can be continued with increased facilities at 

 subsequent meetings, promises to become one of the most im- 

 portant features of the section's meeting 



EVOLUTION AND CLASSIFICATIONS 



A S we have gathered up the scattered masses of botanical 

 ■^"^ knowledge, laboriously wrought out by many isolated 

 workers, and attempted to fit tliem together into a consistent 

 whole, which should outline the structure of the temple Kotany, 

 we have found that the workmen have not always followed the 

 same architectural plan, and have often used different units of 

 measurement. With the increasing specialisation so noticeable 

 year by year there is a corresponding lack of coordination of 

 work. To this lack of coordination, this want of unity of 

 measurement, this misunderstanding of plan, we can no longer 

 close our eyes, and I therefore feel free to invite your attention 

 to the following somewhat summary discussion of tlie causes of 

 the present unsatisfactory condition, in the hope that we may 

 thereby be enabled to see how we may make some improve- 

 ment. • 



All botanical knowledge finally culminates in some kind of 

 classification. The facts of histology, morphology, and phy?i- 

 ol(^y are of great biological importance, but the greatest of all 

 liiological facts is that the world is peopled with living things. 

 We may group and arrange in orderly sequence the histological 

 facts of the science ; we may do likewise with the facts which 

 the morphologist has discovered ; we may make a classification 

 of all the known physiological (nets ; but beyond and above 

 these lies the greatest grouping of all — the grouping in orderly 

 sequence of the organisms themselves whose histology, mor- 

 phology, and physiology we have studied. 



It is now a full third of a century since a great light was first 

 turned upon all biological problems by the formulation of the 

 doctrine of evolution by the master-mind of Darwin. In its 

 light many puzzles have been solved, and many facts hitherto 

 inexplicable have been made plain. We now know what rela- 

 tionship means, and we have given a fuller meaning to the 

 natural system of classification. From the new point of view a 

 natural classification is not merely an orderly arrangement of 

 similar organisms. It is an expression of genetic relationship. 

 Furthermore, in the light of evolution we now see the meaning 

 of many reduced structures whose significance was formerly not 

 at all — or but vaguely — understood. We have become familiar 

 with the fact that degradation is a prominent factor in the vege- 

 table kingdom. Evolution has by no means always involved an 

 advance in structural complexity. Often this catagenesis is a 

 result of parasitism or saprophytism, as is so well illustrated in 

 the "fungi," where the degradation has gone so far that their 

 relationship has to a great degree been obscured. 



But there are also many cases of a catagenesis not due to a 

 dependent habit in which we have evidence of a simplification 

 from a more complex structure. Thus in the willows and 

 poplars, where we have a raceme of very simple flowers, each 

 consisting of a single ovary, or one 'to many stamens, it is 

 readily seen that this simplicity is not primitive. The ovaries 

 are not single carpels, but are composed of two or three united. 

 The flower of the willow is simple by a degeneration from a 

 higher type — probably a tricarpellary or pentacarpellary type — ■ 

 by the loss of its floral envelopes and stamens or pistils. 



Every naturalist should be as familiar with these illustrations 

 of evolution by simplification as he is with those of evolution by 

 complication. In the growth of the great tree of life, while the 

 development has been most largely in an upward direction, so 

 that the great body of the tree has risen far above its point of 

 beginning, there are yet multitudes of twigs and branchlets 

 which droop downward. 



I need not now, before a body of scientific men, speak of 

 evolution as an hypothesis ; for we know it as a great biological 



1 -Abstract of Annual Address before Section G (Botany) of the American 

 Association for the Advancement of Science. By C. E. Besjey, ['resident 

 of the Section. 



fact, about whose existence there is no shadow of doubt. A 

 natural classification will conform strictly to the lines of evolu- 

 tion, it will be in fact a clear exposition of the succes-ive steps 

 in its progress. In such a classification the primitive forms 

 will precede the derived ones, and the relation of the latter will 

 be positively indicated. Moreover, in such a system there wilt 

 be no confusion between the primitively simple forms and those 

 which are so by derivation. 



An examination of our common systems shows them sadly 

 deficient in the essentials of a scientific classification. This is 

 particularly true of the treatment of the flowering plants at the 

 hands of English and American botanists. Nothing could show 

 better the conservatism of botanists than the fact that for a third 

 of a century after the general acceptance of the doctrine of 

 evolution they are still using so crude an arrangement of the 

 group of plants with which they are most familiar. 



I may assume that it is well known to nearly all of us that 

 the prevailing arrangement of the Dicotyledons does not repre- 

 sent the later views of any of the systematists. The fact is 

 that the systematic disposition of the higher plants is at present 

 a make-shift, maintained by conservatism, and a reverence for 

 the time-honoured work of the fathers. It is unscientific to let 

 our practice drag behind the present st.-ite of our knowledge : it 

 is far more so for us to cling to the opinions of our fathers, 

 through mere reverence, long after we know them to be unten- 

 able. It is npt to the credit of our science that for a second 

 time she has persistently held to a system through such con- 

 siderations. For thirty or forty years after a natural system had 

 been constructed by Jussieu, botanists as a body still adhere to 

 the artificial system of Linne. Now, sixty years later, we find 

 ourselves faced wiih a problem similar to that which Lindley, . 

 Torrey, Beck, and Gray met. History repeats itself with such 

 exactness that, with the change of a word here and there, the 

 arguments fro and coti then used may be used to day. The 

 system of Jussieu and DeCandolle is now as much a clog and a 

 hindrance to the systematic botany of the higiicr jilants as was 

 that of Linne sixty years ago, and now as then it is the spirit of 

 conservatism and of veneration for time-honoured usage which 

 maintains the incubus. 



Manifestly a system of classification which conforms to 

 and is based upon the doctrine of evolution must begin with 

 those forms which are primitive, or which as nearly as may be 

 represent primitive forms. Since the flower is a shoot in which 

 the phyllomes are modified for reproductive purposes, that 

 flower in which the phyllomes are least modified must be 

 regarded as primitive, while that in which there is most modi- 

 fication must be regarded as departing most widely from the 

 primitive type. The simple pistil, developed from a single 

 phyllome, is primitive and lower, the compound pistil is 

 derived and higher. The several seeded compound ovary must 

 be lower, and the compound ovary with but one seed 

 must be higher. Separate stamens are primitive, united 

 stamens, whether the union be with one another or with other 

 structures, must be derived and consequently higher. So, too, 

 when all parts of the flower are separate it is a primitive con- 

 dition, and when they are united it is a derived structure. 



Applying these principles to the flowering plants it becomes 

 evident that in the Dicotyledons either the Apetaire or the 

 Polypetalce must furnish our starting point. The Gamopetalae 

 are universally admitted to be higher than the groups just 

 mentioned, and certainly do not contain the sought for primitive 

 types. Even a hasty examination of the thirty-six apetalous 

 families shows that they are, at least to a very large extent, 

 derived from the Polypetalfe by the abortion of some parts and the 

 entire omission of others. It will not be difficult to determine that 

 ' the Ranales must take rank below all other Polypetalse, in the 

 ; sense of representing more nearly than any other group the 

 primitive Dicotyledons. 



The attempt to make a natural system by linking family to 



family in a long undulating chain, by concatenation, is 



unscientific because it absolutely fails to conform to the law of 



I evolution. We must abandon the old classification and attempt 



! one which in the light of evolution is rational. Let us not 



I cling to the old because it is inconvenient to change, let us not 



i cling to it through a mistaken reverence for the practice of the 



fathers, let us net cling to it as long as a flaw may be fo;md in 



a new system. .Science is ever abandoning the old when the 



old is no longer the tiue ; it tears down tliewotk of years when 



that work no lorger reprt;cntsthc truth ; and it dares to reach 



NO. 1248, VOL. 48! 



