678 LIFE : OUTLINES OF GENERAL BIOLOGY 



extraordinarily diverse, I finally perceive, after mature considera- 

 tion, and recognise nothing beyond leaves and stem (for the root 

 may be regarded as a stem). Consequently all parts of the plant, 

 except the stem, are modified leaves." But Wolff went further and 

 raised the question — still before us to-day — how the modification or 

 "metamorphosis", as it was then called, had come about. "We must 

 investigate the causes which so modify the general mode of growth 

 as to produce, in the place of leaves, the parts of the flower." Wolff's 

 own theory was that the transformation was due to a diminution 

 of vegetative vigour {vegetatio languescens). 



More than twenty years after Wolff, the poet Goethe was led 

 "through long prosecuted studies" to the same conclusion. In his 

 famous essay of 1790, Versuch die Metamorphose der Pflanzen zu 

 erkldren, the doctrine of the fundamental unity of floral and foliar 

 organs is clearly enunciated, and supported by arguments from 

 anatomy, development, and teratology. All the appendicular organs 

 of a plant are thus modifications of one fundamental organ — the 

 leaf, and all plants are in like manner to be viewed as modifications 

 of a common type — the Urpfianze. Wolff was ahead of Goethe in 

 his de\elopmental evidence of "metamorphosis"; but the morpho- 

 logy of his day was not sufficiently advanced to give him any clear 

 idea of what it was that had been the subject of all the supposed 

 metamorphosis. He had not a well-defined morphological and 

 cmbryolcjgical conception of the leaf. He felt this himself, as he 

 frankly says, and he was also puzzled by the possibility of reading 

 the facts in two ways: Has the metamorphosis been from vegetative 

 leaf to floral leaf, or has it been in the opposite direction? "For", as 

 he said, "we can as well say a stamen is a contracted petal as we 

 may say of the petal that it is an expanded stamen ; or that a sepal 

 is a contracted foliage-leaf, as that a foliage-leaf is an expandodsepal." 



It is clear nowadays that the stamens and carpels are not simply 

 transformed foliar organs, as might be said of sepals and petals, for 

 they bear specialised spore-making organs or sporangia, namely, 

 the anthers and the ovules. But while some botanists regard the 

 spore-producing leaf or sporophyll as a transformed foliage-leaf, 

 there are others who maintain that the foliage-leaf is a transformed 

 sporophyll which has become sterile. As Vines says, "The view that 

 the foliage-leaf is the primitive leaf-member, and that the floral 

 leaves are its derivatives, is based upon the fact that, as a rule, the 

 vegetative precede the reproductive organs in ontogenesis. The 

 opposite view, that the most highly specialised floral leaf, the sporo- 

 phyll, is primitive, is based upon the fact that, phylogenetically, 

 the reproductive precede the vegetative leaves." In any case, the 

 general homology of folial and floral organs is admitted. 



Note on Morphology of Vascular Plants. — Nearly a century 

 ago, when the colonial nature of .so many Hydrozoa, corals, Bryozoa, 



