246 VEGETABLE ORGANOGRAPHY. 



the different species oi Strelitzia of the gardens presents 

 an analogous result; their petiole is sheathing at the 

 base, afterwards cylindrical, tapering a little upwards ; 

 at its extremity it bears a very distinct limb, which is 

 large in Strelitzia regina, half the size in S. parvifoUa, 

 and completely absent in S. juncea, in which the organs 

 which are called leaves are petioles. 



To the foliaceous organs of Monocotyledons, which 

 are of the same nature throughout, and in which it is 

 impossible to distinguish a petiole or limb, such as the 

 Hyacinth or Aloe, &c. the name of leaves has been 

 given, which would seem to indicate that they are 

 regarded as sessile limbs ; but as this idea has been 

 admitted without any examination, and at a time when 

 no one knew any thing of the degenerations of organs, 

 the question remains thus : — are these the limbs of 

 leaves devoid of petioles, or petioles devoid of limbs? 



I incline to the last opinion, for the following reasons : 

 — 1st. The analogy of these organs with leaves, where 

 a limb and petiole are constantly recognised, is evident. 

 If Strelitzia juncea has only petioles, it is difficult to 

 believe that the pretended leaves of Littcea can be of 

 another nature. If the sheath which supports the limbs 

 of Epidendrum be a petiole, it is difficult to maintain 

 that the sheath of other Orchidess is not one also. If 

 the sheath of the Gramineae be a petiole, why are the 

 sheathing leaves of neighbouring families anything else ? 

 2d. In the two classes of Vasculares we know many 

 examples of sheathing petioles, but none of sheathing 

 limbs. All the limbs of leaves, whatever the disposition 

 of their nerves, contract at the base, and present at this 

 point a divergence of their fibres, more or less distinct ; 

 it is observed in the limbs of the Aroidese, Potamoge- 

 tons, Palms, &c. as in Dicotyledons : it is in this diver- 

 gence that consists the idea of the limb and the spreading 



