ITS MBTAMORPHY. 169 



305. It will be understood that metamorphosis, as applied to 

 leaves and the like, is a figurative expression, adding nothing to 

 our knowledge nor to clearness of expression, but rather liable 

 to mislead. The substance of the doctrine is unity of type. Its 

 proof and its value lie in the satisfactory explanation of the facts, 

 all of which it co-ordinates readily into a consistent and simple 

 system. As applied to the flower, two kinds of evidence may 

 be adduced, one from the normal, the other from teratological 

 conditions of blossoms. The principal evidence of the first class 

 is that supplied by 



306. Position and Transitions. As illustrated in the preced- 

 ing chapter, the flower occupies the place of an ordinary bud or 

 leaf-bud. Also the parts of the flower are arranged on the 

 receptacle as leaves are arranged on the stem, i. e. they conform 

 to phyllotaxy, as well in passing from leaves and bracts to the 

 perianth, as in the position of the floral organs in respect to each 

 other. This is partly shown in the preceding chapters, and 

 is to be further illustrated. Sepals, petals, stamens, and 

 pistils are either in whorls or in spirals, and have nothing 

 in their arrangements as to position which is not paralleled in 

 the foliage. 



307. The evidence from transitions has to be gathered from a 

 great variety of plants. Very commonly the change is abrupt 

 from foliage to bracts, from bracts to calyx-leaves, from these to 

 corolla-leaves, and from these to stamens. But instances abound 

 in which every one of the intervals is bridged by transitions or 



a second edition 1819 ; a third (revised by Alphonse DeCandolle), in 1844, 

 is posthumous. The Organographie Vegetale, in which the morphology of 

 the earlier work is developed, appeared in 1827. The leading idea is that 

 of symmetry, of organs symmetrically disposed around an axis (the 

 homology of foliar and floral organs not at first apprehended), but this 

 symmetry disguised or deranged more or less by unions (solderings) of 

 homogeneous or heterogeneous parts, by irregularities or inequalities of 

 growth, by abortions, &c. 



The reason why the organs in question have a normal symmetrical dis- 

 position on the vegetative and floral axes was not reached by DeCandolle, 

 nor was it perceived that the arrangement of leaves and of floral organs was 

 identical. All this was the contribution of phyllotaxy, a subject which 

 was approached by Bonnet (an associate of DeCandolle's father), and first 

 investigated by the late Karl Schimper and Alexander Braun, beginning 

 about the year 1829. 



It is interesting to know that Wolff's work was wholly unknown to 

 Goethe in 1790, and that both Wolff's and Goethe's were unknown to DeCan- 

 dolle until after the publication of the second edition of the latter's The'orie 

 El&nentaire, in 1819. When the Organographie appeared, the essay of Goethe 

 had come to light ; and contemporary contributions to floral morphology by 

 Petit-Thouars, R. Brown, Dunal, and Boeper, were adding their influence. 



