ECCENTEIC GROWTH. 279 



axis showing the greatest growth ; and when, as is so commonly 

 the case, the displacement of the growth-centre is toward the 

 upper side of the shoot, the largest side of the leaf, as also the 

 largest leaves, will be toward the lower surface. 



Similar generalisations apply to the structure of leaf-pinnules, 

 in which the largest lobe is necessarily on the side nearest the 

 base. This was, in fact, the conclusion reached by De Candolle 

 from empirical observation, and may be taken to indicate that the 

 great majority of cases obey these structural conditions. The 

 reverse effect does, however, occur in a few cases, notably in 

 the example of Goldfussia, a decussate type,* and to these the 

 teleological explanation may be more safely applied: the only 

 point to which attention is directed at present being that such 

 apparent exceptions do not disprove the general mathematical 

 basis of the construction mechanism. Teleological interpretations 

 which seem to satisfy some cases but not others are never wholly 

 satisfactory; but that secondary specialisations may be super- 

 imposed on the primary construction would be naturally expected.f 



* Cf. Qoebel, Organography, p. 112. 



t As an example of a comparable phenomenon in which the primary 

 condition of eccentricity is apparently reversed by a secondary specialisation 

 which takes the form of a later development of eccentricity in a diametrically 

 opposite direction, the case of the development of the typical Papilionaceous 

 flower may be taken, and the same holds for many cases of specialised 

 zygomorphic flower-shoots. Thus, in Oytisus Lahurmwn, longitudinal sections 

 of the perennating buds in January show that all the floral members are laid 

 down in position on a markedly eccentric receptacle ; the anterior side being 

 twice as large as the posterior, the anterior members also exaggerated ; so that 

 the conventional interpretation of ascending development is obvious. The 

 same eccentricity persists on until the anthers are fully formed and the ovules 

 produced inside the carpel (March) ; but as the mechanism receives its final 

 adjustment in the colouring buds, the growth of the posterior side of the flower 

 is considerably increased, i.e. the eccentricity is reversed, and the posterior 

 petal becomes the largest, and the posterior side of the receptacle is thrown up 

 as a considerable elevation, giving the axis that semi-crateriform condition which 

 has induced systematists to describe the type as " perigynous." 



Similarly, in Viola odorata, longitudinal sections of young buds cut in March 

 show all stages in floral development, and may be accurately plotted by cam. 

 lucida. The same phase of "ascending development" indicates a structural 

 eccentricity in the system, and is also expressed in the unequal development 

 of the floral receptacle, the anterior side being again considerably larger than 



