138 report — 1859. 



Wolf, and to a less extent by Linnaeus. Instances were cited to show that Goethe, 

 by reason of what he wrote on the nature of buds, their homologies with seeds, the 

 phenomena of vegetative reproduction and growth, the successive production of node 

 after node, the doctrine of alternate expansion and contraction, &c, may fairly be 

 considered as the pioneer of the doctrine of the rejuvenescence of plants, of the 

 theory of the vibrations of the metamorphosis, and, to a less extent, of that of 

 metagenesis. 



The paper concluded with some remarks on the axis as playing an essential part 

 in the metamorphosis, and on the difficulty in some few cases of distinguishing with 

 absolute certainty between axis and stem, — the author believing that in these cases 

 mere expediency led writers to refer certain organs to the leaf or to the axis re- 

 spectively, and to make the assertion that there are no intermediate stages between 

 stem and leaf. Rather may we not consider leaf and axis as parts of one and the 

 same organ — that in most cases both parts are developed and take part in the meta- 

 morphosis, while in other cases the one predominates over the other ? Is not this 

 view consistent with the absolute identity of original structure and with what we 

 know of cellular growth in the vegetative organs of plants ? Do not all these in- 

 stances of Nature's pliability, as manifested in the metamorphosis, afford a warning 

 against those systematists, who, relying upon some slight or inconstant variation in 

 some one or more organs, found thereupon an unstable, unphilosophical assemblage 

 of genera and species ? 



On the Colours of Leaves and Petals. By W. E. C. Nourse, F.R.C.S., 

 Fellow of the Royal Medical and Chirurgical Society. 



From the facts enumerated by the author, it appears that, 



1st. Variegation of leaves is of two kinds, — that in which the green patch is 

 central, having light-coloured edges ; and that in which the centre is yellowish, 

 with green edges. 



2nd. Variegation is not the result of etiolation, nor yet of any defect or imper- 

 fection of tissue. 



3rd. It is intimately connected with the vital process of nutrition, both in the 

 plant generally, and in the tissue locally, it] some peculiarity of which it seems to 

 consist. That peculiarity, though not a defect, is not connected with exuberance of 

 nutrition. 



4th. In variegated leaves the deepest colours are found in contact with the veins, 

 which is the situation where the growth of the leaf proceeds most rapid] v. 



5th. Light is thus excluded, and the process of growth and nutrition indicated, 

 as the cause of variegation in leaves. 



6th. The first appearance, both of the extra tints of leaves, and of their autumnal 

 tints, whose seat is always in the rete, is invariably either about the capillaries of 

 the upper set of veins, or about the main trunks of the under ones. These two 

 points are therefore evidently the seat of some speciality of function, over which 

 light has a marked influence. 



7th. Leaf- colours thus originate from two different agencies. There are the 

 colours produced in contiguity with the veins, and mainly within the influence of the 

 sap ; and there are the colours produced beyond the full influence of the sap, and 

 chiefly under the control of solar light. Besides these, there is a third set of tints 

 produced by the circulation of a coloured sap, as in beet root, red cabbage, &c. 



8th. White flowers have nothing to do with etiolation or imperfection of tissue, 

 but contain in their cells a white matter perfect after its kind, and attain their fullest 

 development under the full blaze of solar light. 



9th. Brilliant colours are often seen in the rudimentary petals still enclosed in the 

 bud, so that no light could reach them. Such colours are usually in contact with the 

 veins, showing their connexion with the process of nutrition. 



10th. The process of nutrition is one of the most important vital powers the 

 plant possesses, since without it the very identity and existence of the individual 

 must cease. With respect to colour, this power exhibits its effects occasionally in 

 the production of tints quite independently of light, and constantly by the formation 

 of tissues not calculated to take on this or that colour at random, but each sped-' 



