STRUCTURE.] LEAVES OF AMICIA. 293 



with the hairs that are formed on young leaves ; it is there- 

 fore no exception to the general rule that leaves grow by 

 their base. 



"Formation of the Leaves o/Amicia Zygomeris, D. C. The 

 axis of the leaf-bud is originally shaped like a conical tumour 

 that afterwards becomes a cylinder with a large base, and a 

 convex projecting apex. A little below the top, there appears 

 a small excentricity, which gradually becomes a tumour, and 

 is turned off nearly horizontally from the top of the axis. 

 The base of the tumour extends a little on the periphery of 

 the axis, at the same time that its summit is raised, and 

 passes beyond it. 



In a short time, the tumour becomes a fleshy, expanded 

 scale, with three bosses, of which one, the oldest and largest, 

 is terminal, whilst the other two are still continuous with 

 the axis. At this time a line drawn across the axis to 

 the top of the scale, was found to be / to -/ ff lines long ; 

 about one half of this length belongs to the diameter of 

 the axis, so that the length of the leaf at this stage of its 

 development, can be estimated at -^ lines. Two other bosses 

 are afterwards formed on the axis, one on each side; the 

 scale is then a simple, convex leaf, with five unequal bosses ; 

 the terminal boss corresponds with the point of the com- 

 mon petiole, the four others become leaflets. The leaf in 

 this imperfect state, undergoes many other transformations. 

 It is remarkable that the terminal boss, originally the largest, 

 is gradually absorbed, as it were, by the developing leaflets. 



At the same time that the tumour, corresponding with the 

 point of the common petiole, is formed on the nucleus of the 

 axis, we find round the latter a slight rim, below, and having 

 no connexion with the petiolar tumour. Another rim, on 

 the opposite side of the axis, corresponds with the former 

 one ; they are both at first quite distinct from each other, 

 but they soon approach and unite by their lower edges, 

 whilst they remain constantly free above. The two points 

 of contact always meet on the same points of the periphery 

 of the axis, because each of the two rims occupies half of 

 the surface of the nucleus. One of these points is placed 



