292 VEGETABLE ORGANOGRAPHY. 



opposite leaflets, the side most developed is always the 

 lower, the upper being narrower and less prolonged. 



In leaves with palmate, peltate, or pedate nerves, 

 when thei'e is inequality in the two sides of the leaflets, 

 or lobes, the external are always those which are de- 

 veloped most, probably because their development is 

 not restrained by the neighbouring parts. The same 

 observation may be made upon the stipules, which are 

 very frequently irregular, the outer side, or that most 

 distant from the petiole, having a tendency to be dilated 

 much more than the inner, whence it results that several 

 of them have the longitudinal nerve very near the inner 

 edge, and their general form is semiovate, semicordate, 

 or semisagittate. 



The inequality of the two sides of a compound leaf is 

 also perceptible in certain leaves, in some of the sides 

 being devoid of a leaflet, the existence of which is indi- 

 cated by the general symmetry ; thus, Anthyllis tetra- 

 phylla, and all the species of Anthyllis of the section of 

 Cornicineae, are devoid of a leaflet or a stipule towards 

 the base of one of the sides of the leaf. Thus, in several 

 species of Mimosa (PI. 13, figs. 2, 2*,) the common petiole 

 of which bears two partial ones, each of which wants a 

 leaflet of the lower pair of the inner side, this absence 

 is owing to a constant abortion, for the place of the 

 leaflet is vacant, and in some accidental cases it is 

 developed. 



Not only have leaves, considered with regard to them- 

 selves, their sides symmetrical, but they also almost always 

 present a symmetry in size, when they are considered with 

 regard to their position upon the stem. Thus, in almost 

 all opposite or verticillate leaves, those which spring 

 from the same horizontal plane are perceptibly equal. 

 Sometimes, in verticillate ones, they are alternately a 

 little unequal ; but in opposite ones there has recently 



