STRUCTURE OF FLOWERS. 129 



pose them and find more or less clearly the trace of the 

 petiole and limb : the former being developed in the 

 outer organs which serve as the integuments, and the 

 latter in the interior and reproductive organs. Thus, in 

 the calyx, the sepals represent usually dilated petioles, 

 more or less fibrous or foliaceous : sometimes the limb is 

 visible, as in the Rose. In the corolla, the petals appear 

 generally formed by the petiole dilated into a petaloid 

 limb ; sometimes they present a claw, which acts the part 

 of a petiole, and a lamina, which acts that of a limb. In 

 the stamens we may also distinguish the filament which 

 represents the petiole, and the anther which is formed of 

 the two margins of the limb rolled upon themselves, 

 thus forming two cells. Lastly, in the carpels it hap- 

 pens most frequently that the petiole is wanting ; the 

 limb forms the carpel and the ovules arise from the ex- 

 tremity of the lateral nerves. 



The petiole sometimes exists in the carpels (for exam- 

 ple, in Sterculia, Phaca, &c.) and then they are pedicel- 

 late; but when there are several carpels with the petioles 

 united, we must take care not to confound this support, 

 which seems an axis (as in Helleborus), with the central 

 axis, which is the prolongation of the stem (as in Myosu- 

 rus). I do not know any general rule for distinguishing 

 them. The extremity of the carpels is prolonged into 

 a style, which arises from the point where in a great 

 number of leaves we see a bristle or mucro, or a terminal 

 tendril, which is therefore the rudiment of this organ. 



The important differences which are observed between 

 the ordinary or nutritive leaves, and those which com- 

 pose the flower, are : — 



1st. That the ordinary leaves bear a bud in their axil, 

 and rarely have germs developed at the extremity of their 

 nerves (except in Bryoplujllum) ; those, on the contrary, 

 which form or surround the flower have no axillary 



VOL. II. K 



