2 Mr. J. Ball on the genus Leontodou. 



the variations in whose form and structure the characters of the 

 species have been derived. 



The structure of the root has been, as far as I am aware, neg- 

 lected by all authors before Koch, and by many who have written 

 since the publication of his work ; it offers nevei'theless a very 

 valuable character by which plants, which in certain states nearly 

 resemble each other, may with certainty be distinguished, and I 

 altogether concur in the sepai'ation of the group of species 

 which possess a fusiform vertical root, as a distinct section of 

 the genus from those having a horizontal abruptly terminated 

 rhizoma, though it is proper to remark that L. Villarsii, Lois., 

 and L. Rosani, Ten., present a nearly intermediate structure, in 

 conformity with the general law by which the nexus in a series 

 of forms so complete as that of the Cichoracece is continually 

 maintained. 



The length of the scape or flowering stem, as compared with 

 that of the leaves, can scarcely be deemed a trustworthy cha- 

 racter; in L. Taraxaci, Lois., and perhaps also in L. croceum, Hke., 

 the comparative shortness of the scape appears to be constant 

 under all circumstances. That condition of the scape which is 

 indicated by the drooping of the capitulum before flowering, as 

 also the thickening of the upper portion of the scape, and the 

 presence of leafy scales, are characters, which, though properly 

 applicable to the description of certain species, are yet so variable 

 in degree, that individual specimens may often be found to which 

 specific characters drawn from these points scarcely if at all apply. 



The variations in the form of the leaves in the several species 

 furnish characters, which it is impossible to neglect, and yet, 

 owing to the great diversity seen amongst individuals of the same 

 species, which it is extremely difficult to define with accuracy. 

 I may here express an opinion which has often been suggested 

 to me in the course of attempts to unravel difficult groups of 

 species, that the chief advance to be made in descriptive botany 

 depends upon such accurate observation and designation of 

 the forms of the leaf, as will enable us to comprehend in specific 

 characters the phases of variation which the leaves of the same 

 species undergo. Careful observation shows, as theory would 

 have already suggested, that, amidst their endless variations, the 

 leaves of plants belonging to distinct species are seldom if ever 

 precisely similar, but the descriptive botanist frequently fails in 

 assigning distinctive characters which really exist in nature. In 

 Leontodon the depth of the incisions or indentations of the leaves 

 is a point of little or no importance, but perhaps their direction 

 has not been sufficiently attended to, I venture to think that 

 in this respect Koch's appreciation of the importance of the cha- 

 racters drawn from the leaves is erroneous. I am also disposed 



