September 30, 1909J 



NA TURE 



407 



appreciation. He can pursue his studies unaffected by any 

 considerations save those of adding to the sum of human 

 knowledge and of bringing a necessary task appreciably 

 nearer completion. In descriptive study it is the work 

 rather than the personality of the worker that tells. Yet 

 the work is not without human interest, because systematic 

 writings rarely fail to rellect the character of the writers. 

 The intimate knowledge of descriptive treatises, which 

 floristic or monographic study entails, usually leads to 

 mental estimates of the actual authors. The evidence on 

 which these estimates depend is unwittingly given and un- 

 consciously appreciated. But its value is not thereby 

 diminished, and estimates so formed may prove useful 

 checks on contemporary judgments. 



The descriptive worker as a rule makes his work " the 

 primary business of his life, which he studies and practises 

 as if nothing else in the world mattered." But he does 

 not hold aloof from those engaged in other lines of 

 botanical activity. His evidence is mainly obtained from 

 organography and organogeny ; but, just because his results 

 are for the use of others, the descriptive botanist has to 

 keep abreast of all that is done in every branch of his 

 science. New weapons are constantly being forged, and 

 not in morphological workshops only ; with these and their 

 uses the descriptive worker must be familiar, for the need 

 to employ them may arise at any moment. If he does not 

 always abandon old friends for new, this is not because 

 the systematist is unaware of their existence, or unpre- 

 pared to apply new methods. The descriptive worker 

 employs his tools as a craftsman ; like other craftsmen, he 

 finds that tools do not always fulfil the hopes of their 

 designers. In descriptive work, too, as elsewhere, a steam 

 hammer is not required to break every nut ; the staff and 

 sling may be arms as effective as those of the hoplite. 

 There are occasions when the descriptive writer does appear 

 to hold aloof by declining to accept proffered evidence. 

 But his motive is not arrogant ; it is only altruistic. If he 

 is to avoid the risk of causing those who depend on his 

 results to reason in a circle, the descriptive writer must 

 obtain these results, if not without extraneous aid, at least 

 without help from those for whose immediate use they are 

 provided. 



Taxonomic study is pursued in an environment which 

 differs from th.it surrounding descriptive work. Tile de- 

 scriptive student can hardly see the wood for its trees. 

 The taxonomic student works in more open country, and 

 can look on the wood as a whole. He has, too, the benefit 

 of companionship. The paUeobotanist meets him, with all 

 the lore of mine and quarry, as one ready to exchange 

 counsel ; other workers attend to give or gather informa- 

 tion. 



The community of interest which unites the systematic 

 worker, chiefly concerned with existing plant-types, and 

 the palseobotanist, primarily interested in types now extinct, 

 is strengthened by the bond which identity of purpose 

 supplies. But the two are differently circumstanced ; the 

 systematic worker is ordinarily better acquainted with the 

 characters than with the relationships of his types ; the 

 pala?obotanist usually knows more of the relationships of 

 his types than he does, or ever may do, of their characters. 

 The material of the pateobotanist rarely lets him rely on 

 ordinary descriptive methods in defining his plants ; he has 

 to depend largely on anatomical evidence, which supple- 

 ments and confirms, but hardly replaces, the data of 

 organography. On the taxonomic side the palaeobotanist 

 is restricted to phylogenetic methods ; here again he is 

 handicapped, though less than on the descriptive side, by 

 the fragmentary character of his specimens. The palaeo- 

 botanist hardly does more than the phylogenist, hardly as 

 much as the anatomist, towards advancing the object all 

 have in common. 



The same community of interest unites in their labours 

 the organographic systematist and the morphologisi whose 

 interests are phylogenetic. Here, however, though the task 

 of the two be complementary, the mode of attack is so 

 different as almost to mask their identitv of purpose. The 

 comparative morphologist studies the planes oT cleavage 

 indicated by salient differences in structure and develop- 

 ment. The system he evolves is composed of the entities, 

 sometimes more or less subjective, that combinations of 

 characters supt'est. The method in intention, and largely 



NO. 2083, VOL. 81] 



in effect, passes from the general to the more particular, 

 though the process is tempered by the fact that the 

 characters used are derived from such types as exhibit 

 thorn. The organographic systematist, after summing up 

 the characters which mark individual types, aggregates 

 these according to their kinds. Having estimated the 

 features that characterise individual kinds, he aggregates 

 these according to their families. Families are thereafter 

 aggregated in higher groups, and these groups are sub- 

 jected to further aggregation. The system thus evolved is 

 composed of those entities, always in theory objective, 

 that successive aggregations indicate, and the process is 

 one of constantly widening generalisation. 



The comparative morphologist, though glad when his 

 results can be practically applied, follows truth for its own 

 sake. His work is thus on a higher plane than that of 

 the organographic systematist, whose aggregations are 

 primarily utilitarian. But the work of the latter is not 

 less valuable because its scientific character is incidental. 

 Were our knowledge of plant-types exhaustive, a generally 

 accepted artificial arrangement of these would be as useful 

 to the applied botanist as a professedly natural one. But 

 our knowledge is incomplete, and the accession and inter- 

 calation of new types renders any artificial, and most 

 attempts at a natural, system sooner or later unworkable. 

 The more closely an arrangement approximates to the 

 natural system, the less can the intercalation of new forms 

 affect its stability. The more stable a system is, the mors 

 easily will its details be remembered and the more useful 

 will it prove in practical reference work. Here, therefore, 

 for once, self-interest and love of truth go hand in hand. 



Since the organographic systematist learns their 

 characters from his groups, while the comparative morpho- 

 logist defines groups by the characters he selects, their 

 results, were knowledge complete, should be identical, and 

 this identity should prove their accuracy. But knowledge 

 is finite, and these results are not alwaj's uniform. The 

 want of uniformity is, however, often exaggerated because 

 the reasons are not always appreciated. 



One cause is the difference in personal equation, which 

 affects alike the worker who deals with things and him 

 who considers attributes. It would be contrary to expectar 

 tion vi-ere every phylogenist to assign the same value to 

 each character, or every systematist to apply the same 

 limitation to each type or group of types. The divergence 

 of view on the part of two observers may show a small 

 initial angle ; it may nevertheless lead them to positions far 

 apart. But while divergence of view is the most obvious 

 explan.ation of the want of uniformity apparent in 

 systematic results, it is the least effective cause. This 

 inherent tendency to differ manifests itself in contrary 

 directions ; in the long run individual variations are apt 

 to cancel each other. 



The nature of the work counts for more than the pre- 

 disposition of the worker. The aggregations on organo- 

 graphic lines, which were the main guides to the composi- 

 tion of the higher groups until phylogenetic study was 

 seriously undertaken, do not assist the comparative morpho- 

 logist. The characters on which phylogenetic conclusions 

 may be based increase in value in proportion to the width 

 of their incidence, so that the greater their value for 

 phylogenetic purposes the less do they aid the descriptive 

 worker in discriminating between one plant-type and 

 another. Often they are characters which for practical 

 reasons the descriptive worker must avoid. Organography, 

 then, may not give evidence as to characters whereof 

 cognisance cannot be taken, while for another reason the 

 comparative morphologist may not use characters derived 

 from descriptive sources. The object of the phylogenist is 

 to take his share in advancing our knowledge of taxonomy ; 

 to seek from the systematist the evidence on which his 

 results are based would be to vitiate the reasoning of 

 both. All that the phylogenist can ask the descriptive 

 worker to do is to supply the units that require classifica- 

 tion. 



The comparative morphologist, relying mainly on 

 anatomical and embryological evidence, at first had a hope 

 that his method of study might enable him to supply his 

 own units and thereby render further taxonomic work 

 based on organography unnecessary. This hope remains 

 unfulfilled, and the phylogenist, as a rule, limits his efforts: 



