68 



NA TURE 



[May 20, 1897 



possedais dans nies semis que des plantes a fleurs rouges ; j'avais 

 en triant les sujets pour la reproduction toujours ecarte les fleurs 

 Ics moins brillantes. II s'agissait maintenant d'obtenir des fleurs 

 a couleurs pales. Des efibrts nouveaux furent fait dans cette 

 voie ; je vis au bout de deux ans apres apparaitre la premiere 

 fleur aux petales Wanes et a onglet rouge ; des lors les croise- 

 ments se multiplierent au point qu'apres la neuvieme annee la 

 perfection des formes et des coloris est telle que tous ceux qui 

 voient mes Cyclamen Papilio sont unanimes a reconnaitre leur 

 merite et leur perfection des fleurs." 



In this case the basis of the new strain was found in a marked 

 variation or "sport." The deviation from the type could not, 

 however, have been very marked. The most remarkable feature 

 in " Papilio " as now developed is the curled and toothed margin 

 of the corolla segments. These peculiarities repeat characters 

 which occur elsewhere in the order. In Soldatiella the toothing 

 is conspicuous : curling occurs in cultivated varieties of Primula 

 sinensis. It is interesting to observe in "Papilio" that in the 

 primary variation there was a correlation between the toothing 

 of the corolla segments and of the leaves. 



Crestittg. 

 The most remarkable form which has made its appearance 

 under cultivation is that in which a plumose crest has developed 

 on the inner surface of each corolla segment. This is shown 

 in Fig. 10, which represents the " Bush Hill Pioneer," raised 

 by Messrs. Hugh Low and Co. I quote the account of its 



development with which they have been so good as to furnish 

 me : — 



"This interesting variety was first observed in our nurseries 

 some four years since, but how it originated we are unable to 

 say. 



" At that time, the only peculiarity about the variety was a 

 very slightly raised rib running part of the way up the petals, 

 and showing no tendency to branch. This was, however, con- 

 sidered sufficiently curious to follow up, and we seeded it with 

 its own pollen. 



" The young plants from this showed a decided improvement y 

 the rib in some cases showing a marked tendency to branch. 

 The best varieties (ten in number) were again fertilised with 

 their own pollen, and the plants now being exhibited by us 

 have resulted, although, needless to say, they are among the 

 finest obtained up to the present, though all show a further 

 improvement, eveiy flower having a well-branched feather on 

 the petals. 



" We have this year found some colour in one plant, and we 

 believe we shall have no trouble in obtaining crested flowers in 

 a variety of colours." 



The corolla segments of Cyclamen have no mid-rib. The 

 appearance of such a structure is a reversion to the original 

 leaf-type. The development of a crest from a mid-rib carries 

 reversion very far back indeed. The branching of a leaf- 

 structure in the plane in which it is expanded is common 

 enough ; branching in a plane at right angles to this is rare. 



NO. 1438, VOL. 56] 



Leafy outgrowths frequently occur from the mid rib in the 

 cabbage (Masters' "Teratology," p. 455). In this case the 

 structure of the leaf approximates to that of a stem, of which, 

 indeed, the leaf may be regarded as a modification. 



An interesting fact with regard to this singular variation is 

 that it has appeared more than once, and independently. It 

 first occurred in 1885, but seems afterwards to have been lost 

 sight of {Gardener's Chronicle, 1885, p. 536). It has also 

 occurred in a red-flowered form in France {Revue Horticole, 

 1897, pp. 98 and 130), in which case it was also perpetuated 

 by seed. 



I have not succeeded in discovering any similar structure in 

 any primulaceous plant occurring in a wild state. Dr. Masters, 

 however, informs me that it has been observed in cultivated 

 forms of Primula sinensis. The tendency thus seems to be 

 latent in the order, though why it should be so I am unable to 

 explain. 



Some theoretical interest appears to me to attach to the rapid 

 development of so striking an ornament of a corolla segment. 

 Such appendages are frequent enough in orchids, and are re- 

 garded as adaptations to cross-fertilisation by insects. Their 

 gradual evolution might be thought to require a long period 

 of time ; but in the present case we have definite evidence 

 that such a structure may be developed by selection with great 

 rapidity. 



Concbision. 



(i) The facts which I have stated appear to me to establish 

 the result that, when once specific stability ^ has been broken 

 down in a plant, morphological changes of great variety and 

 magnitude can be brought about in a comparatively short space 

 of time. This appears to me to have a very important bearing 

 on the rate of evolution. Mr. Darwin quotes Lord Kelvin as 

 insisting " that the world at a very early period was subjected 

 to more rapid and violent changes in its physical condition than 

 those now occurring"; and he adds, "Such changes would 

 have tended to induce changes at a corresponding rate in the 

 organisms which then existed " ("Origin," sixth ed., p. 286). 

 That changes may be effected with considerable rapidity can- 

 not, I think, be denied. 



(2) It is further, I think, abundantly proved in the present 

 case that, though sudden variations do occur, they are, as far as 

 we know, slight as long as self-fertilisation is adhered to. The 

 striking results obtained by cultivators have been due to the 

 patient accumulation by selection of gradual but continuous 

 variation in any desired direction. 



(3) The size which any variable organ can reach does not 

 appear to be governed by any principle of correlation. Large 

 flowers are not necessarily accompanied by large leaves. Under 

 natural conditions size is controlled by mechanical limitations 

 and by the principle of economy. Nature cannot afford to 

 indulge in anything unnecessary for the purpose in view (see 

 Darwin, "Origin," 6th ed., p. 117). 



(4) The general tendency of a plant varying freely under 

 artificial conditions seems to be atavistic, i.e. to shed adaptive 

 modifications which have ceased to be useful, and either to 

 revert to a more generalised type or to reproduce "characters 

 which are already present in other members of the same group " 

 (see Darsvin, " Origin," 6th ed. , p. 127). This conclusion must, 

 however, be accepted with caution, for we must remember that 

 in a case like the present we are only acquainted with variations 

 which have been preserved with a particular end in view. 



(5) The case of "cresting" shows that the plant still pos- 

 sesses the power to strike out a new line and to develop 

 characters which would even be regarded as having specific 

 value, as in the total change which has been effected in the 

 form of the leaf in Primula sinensis. If such a race developed 

 any degree of sterility with other races, it would have satisfied 

 Huxley's criterion for the artificial production of a new species. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 O.KFORD. — The Savilian Professorship of Geometry being 

 vacant by the death of the late Prof. Sylvester, the Electors 

 will proceed to the appointment of a successor in the course 

 of the present Term. The duties of the Professor are defined 

 in the following provisions of the Statutes: — "The Savilian 



1 For a general discussion of "the principles of variation and specific 

 stability, see Nature, vol. li. pp.'45Q-46i. 



