3i8 



NA TURE 



\\ EBRUARY 6, 1908 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part 0/ Nature. 

 No notice is taken of anotiymous communications.] 



The Cotton Plant. 



Attention has been directed in Nature of January 16 

 to a work in which a writer on economic subjects deals 

 with " The Wild and Cultivated Cotton Plants of the 

 World." The subject is as difficult as it is important, 

 and your reviewer, whose expert opinion is held in regard, 

 shows that some of the questions involved may have two 

 sides. 



Your reviewer remarks that this work has been doomed 

 to failure owing to the mode of study adopted by its 

 author. If this means that the work is not without error 

 and does not attain finality, the judgment has been 

 anticipated by the author. But if this also means that the 

 work adds nothing to what is known by those who do 

 not happen to be experts in cotton, its readers will find 

 that the verdict cannot be sustained. 



The work is compared unfavourably with another on 

 this subject by the late Prof. Todaro. Your reviewer 

 attributes success to Todaro 's book because Todaro dealt 

 for the most part with living plants grown by him from 

 seed. It is possibly true that the material studied by 

 Todaro was, for the most part, obtained from the living 

 plants the cultivation of which is related in the introduc- 

 torv fifth part of his monograph. But it is not the 

 case that Todaro 's revision of the cottons of the world 

 was based for the most part on this material. Those who 

 have studied Todaro 's work know that, of the fifty-four 

 species of Gossypium there enumerated, only eleven were 

 certainly described from living plants, although it is 

 possible that others may have been seen by him in the 

 living state. In dealing with the remaining thirty-eight, 

 Todaro has had to rely on the mode of study which your 

 reviewer tells us is doomed to failure ; indeed, as regards 

 a considerable number of the species recognised, Todaro 

 has had to depend on the accuracy of descriptions by other 

 writers, because he did not have access to authentic 

 herbarium specimens. 



We are, however, less concerned with the work of 

 Todaro than with the continuation and extension of that 

 worJi which your reviewer says was needed, and which 

 Sir G. Watt has tried to supply. A study of Watt's work 

 shows that its chief merit and value He in the exhaustive 

 way in which it brings together references to all con- 

 ceivable sources of information. On this account it will 

 be indispensable to anyone who may hereafter be seriously 

 at work on cotton, who will find it a comprehensive guide 

 to the literature of the subject and to the whereabouts of 

 authentic material. Its readers must follow the rule that 

 applies to the study of subjects so critical, and reserve 

 perfect freedom of judgment as regards the acceptance of 

 Watt's conclusions. They are not bound to agree with 

 Watt as to the provenance or the pedigree of any par- 

 ticular cultivated cotton, nor are they bound to adopt the 

 advice Watt may give as to the kinds most suitable for a 

 particular locality. But when, in deference to other views 

 or on intuitive grounds, we question the validity of Watt's 

 opinion, we are not entitled to do more than reserve our 

 assent unless and until we have critically examined, and if 

 need be supplemented, the material on which that opinion 

 is based. 



Believing, as he explains, that the work of Todaro does 

 not require to be corrected, your reviewer is justified in 

 refusing to accept any opinion expressed by Watt which 

 is at variance with that of Todaro, and is free to 

 imagine that, because Watt at times differs from Todaro, 

 Watt's volume is rather a retrogression than an advance 

 on Todaro 's work. He is also entitled to assert the right 

 to criticise details as to which he considers himself a com- 

 petent judge. But his decision that when Watt differs 

 from Todaro therefore Watt must be wrong does not prove 

 this to be the case ; his belief in the infallibility of Todaro 

 does not establish that unusual quality ; we know, indeed, 

 that at least one of Todaro's species of Gossypium does 

 not belong to the genus. 



NO. 1997, VOL. 'J'j'] 



In exercising his right to criticise, your reviewer 

 occasionally raises a doubt whether sound judgment as 

 to the value of a cotton need include full appreciation of 

 the diflicuhies connected w-ith its botanical status, while 

 his terminology does not make it clear that his conception 

 of botanical characters, and his interpretation of words 

 like " species " and " variety," accord with established 

 usage. This prevents our commenting on his estimate of 

 Watt's system of classification, which is based on those 

 characters that Watt believes to be least subject to varia- 

 tion in truly wild cottons. That among cultivated forms 

 even these characters prove unstable is only loo true; 

 but they may still be the best available, and the re- 

 viewer does not suggest an alternative method of arrange- 

 ment. 



In certain specific instances your reviewer directs atten- 

 tion to what he terms errors. Thus the treatment by 

 Watt of G. obtusifolium, Roxb., and G. Wightianum, 

 Tod., is cited as a case of "erroneous synonymy." The 

 situation is this : — Todaro has shown that he only knevir 

 of G. obtusifolium from Roxburgh's description, and that 

 he did not recognise Roxburgh's species in any of the 

 plants he grew. Todaro has further concluded that a 

 plant which most Indian botanists have treated as a form 

 of G. herbaceum does not belong to G. herbaccuni ; this 

 plant he has named G. Wightianum. Dealing anew with 

 the subject. Watt has agreed with Todaro in considering 

 G. Wightianum distinct from G. herbaceum. But Watt 

 also thinks that he can recognise the plant which Ro.\- 

 burgh named G. obtusifolium, and believes that 

 G. Wightianum is only a variety of G. obtusifolium. 

 However the case may stand as to these conclusions, the 

 synonymy they involve is accurate. Even if, as is possible, 

 your reviewer by " erroneous synonymy " only implies 

 that Watt differs from Todaro, the criticism fails. We are 

 unable to say whether, if Todaro had been able to re- 

 cognise G. obtusifolium, any difference of view would have 

 existed. The subordinate questions as to whether Watt's 

 limitation of G. obtusifolium, var. Wightiana, accords 

 with natural facts, and whether G. obtusifolium proper 

 and G. Nanking^ var. roji, should be kept apart or united, 

 are only differences of opinion between Watt and your 

 reviewer on points as to which they are equally entitled 

 to form a judgment. 



Your reviewer cites two cases in which he believes that 

 plants have been wrongly identified by Watt. He states 

 that the figure of G. microcarpum given by Watt 

 (plate 36) represents a plant other than the one figured 

 by Todaro as G. microcarpum. He points out that Todaro 

 describes the two lobes on either side of the central lobe 

 as unequal, and states that the figure given by Watt does 

 not display this peculiarity. On examining the figure of 

 G. microcarpum given by Watt, we find that it 

 does show this peculiarity, and on consulting the text 

 we see that it is G. microcarpum of Todaro and no 

 other species that is intended to be represented. There 

 may be some mistake with regard to this species ; if 

 it be the case that the G. microcarpum grown by the 

 reviewer is the true G. microcarpum of Todaro, and is at 

 the same time the plant figured by Watt as G. .Schottii, 

 then the figure which Todaro has given of G. microcarpum 

 can hardly represent his own species accurately ; it is 

 unlikely that a suggestion as to the identity of G. Schottii 

 as figured by Watt (plate 35) and G. microcarpum as 

 shown in Todaro's plate will be generally admitted. In 

 the other case, your reviewer's conclusion as to mis- 

 identification rests partly on a statement that the name 

 " Piura " indicates a cotton other than the one it connotes 

 in Watt's book, partly on an assertion that Lamarck 

 describes his species G. vitifolium as having the under- 

 side of its leaves glabrous. The incidence of vernacular 

 names is not always so exact as to justify implicit con- 

 fidence, but in this instance Spruce, who collected the 

 Piura cotton in Peru and has described it with care, 

 assigns the name to tlie plant with which \A'att associates 

 it. Finally, what Lamarck says with regard to the leaves 

 of his G. vitifolium is : — " Elles sont glabres en dessus, 

 un neu velues en dessous." 



What we now await is a work on the cultivated cottons 

 from the pen of your reviewer. D. Prain. 



Kew, January 20. 



