THE LEAVES OF VASCULAR PLANTS. 247 



out of the fibres. But all these leaves spread out at 

 their base as petioles, instead of contracting as limbs. 

 3d. Phyllodia, or petioles without limbs, in Dicotyledons, 

 are terminated either by a spine, like that of Aloes, 

 or by a tendril, as in Flagellaria and Methonica, or 

 by a callosity, as in the Hyacinth, and a multitude of 

 others. These different modes of termination, which 

 indicate an abortion, are found under analogous circum- 

 stances in both classes. 4th. The study of Dicotyledons 

 has proved that there exists a great number of examples 

 of leaves -without limbs, and, consequently, it may 

 equally as well be admitted in Monocotyledons. This 

 phenomenon is, in each class, more frequent in some 

 families than in others. 



I think then that in this class, as in the preceding, 

 there exist: 



1st. Leaves having a limb and petiole : such as, among 

 Monocotyledons, Sagittaria, Potamogeton natans^ Heme- 

 rocallis, Palms, the Gramineae, &c. ; and in Dicotyledons, 

 the Pear, Rohinia, &c. 



2d. Leaves having only a foliaceous petiole, perform- 

 ing the office of a limb, as in the submerged Potamo- 

 getons, Hyacinth, Iris, &c., among Monocotyledons ; 

 the Acacias with phyllodia, Bupleurum., Lathyrus Nis- 

 solia, &c., among Dicotyledons. 



od. Leaves having a true limb devoid of petiole, as 

 those of Trilkm, Paris, Lilium, &c., among Monoco- 

 tyledons ; and all sessile leaves among Dicotyledons. 



Let us observe, on concluding this Section, that the 

 word " leaf" is taken, in woi'ks of descriptive Botany, 

 sometimes for an entire leaf, composed of petiole and 

 limb, which is the more regular and usual case ; some- 

 times for a limb devoid of petiole, as is said of sessile 

 leaves ; sometimes for a foliaceous petiole without a 

 limb, as in the family of the Liliaceae, or in the Mimosas 



