280 PROGRESS OF THE COMPOUND LEAF. [BOOK i. 



This projection is like a rounded tumour, and is the begin- 

 ning of the apex of the terminal leaflet on the side of the 

 axis opposite the tumour, and a little above it, an excentricity 

 belonging to a younger leaf afterwards appears. This excen- 

 tricity becomes a tumour, which lengthens more and more 

 laterally to the axis, whilst its base increases at the expense 

 of the latter, and from its summit to the axis, there is a pro- 

 jecting line terminating on each side of the periphery of the 

 axis in a small swelling ; to this swelling another springing 

 from the axis is soon after added ; a little later five toothings 

 are seen on the edge of a large ovate leafy expansion. These 

 toothings are nothing but the three leaflets and their two 

 stipules, having soon after their birth the appearance of a 

 simple crenated, and afterwards lobed leaf. 



The leaves of roses when they are attached to the axis by 

 a small base also resemble simple, oblong or ovoid leaves, 

 with seven or more toothings ; at this stage they have no 

 trace of either petiole or distinct leaflets. 



The nascent leaflets of compound leaves are, with the 

 exception of the terminal leaflet, symmetrically disposed on 

 the two sides of the petiole ; but when perfectly formed this 

 symmetry is often lost. 



If we compare the form of a compound leaf, when its basal 

 leaflets and stipules have just appeared at the axis, with a 

 young simple leaf we find no difference between them ; for 

 at this degree of development the compound leaf is nothing 

 but a simple leaf. It is not till later, when the constituent 

 parts are no longer in direct relation with, nor form a part 

 of, the nucleus of the axis, that they assume a form corre- 

 sponding with that of a perfectly developed leaf. It is in 

 this, as it were, secondary formation of the parts of a com- 

 pound leaf that there perhaps exists a distinctive character 

 between it and the really simple leaf, from the number 

 of which we must withdraw many forms which are at pre- 

 sent referred to this class ; for, as has been shown by Grise- 

 bach, many parted leaves have not in the beginning all their 

 segments. I have not a sufficient number of observations on 

 the development of decompound or supra-decompound leaves, 

 to be able to enter at present into that subject. 



