SECT. I. ORGANOGRAPHY AND GLOSSOLOGY. 59 



other of its surface, which are properly styled " ap- 

 pendages" to the stem or ascending axis. Diversified as 

 these organs are in their forms, and even in their func- 

 tions, they may all be considered as modifications or 

 transformations of one fundamental organ, of very ge- 

 neral, though not universal occurrence, viz. the leaf. 

 In order to obtain a general notion of the varied appear- 

 ances assumed by this organ, we must suppose that some 

 of the materials which compose the stem have become 

 detached from the rest, and are then given off at the 

 surface, in the form of distinct organs. 



CHAP. III. 



NUTRITIVE ORGANS continued. 



LEAVES, SIMPLE AND COMPOUND (69.). VERNATION (71.). 

 FORMS OF LEAVES (74. ). PHYLLODIA (75.). TRANS- 

 FORMATION OF LEAVES (78.). VENATION (81.). DIS- 

 POSITION AND ADHESION (82.). NUTRITIVE ORGANS OF 



CRYPTOGAMIC PLANTS (84.). 



(69.) Leaves. IN by far the greater number of 

 plants, these organs consist of thin flattened expansions, 

 in which the vascular portion, termed " veins/' or 

 " nerves,'' is arranged in a kind of network, having the 

 interstices rilled up with cellular tissue here termed the 

 " parenchyma ;" and the whole is invested with the 

 epidermis. In Dicotyledons, the vessels proceed imme- 

 diately from the medullary sheath. In a few rare ex- 

 amples, as in the Dracontium pertusum (fig. 51.), the 

 parenchyma imperfectly fills up the interstices between 

 the veins, and large holes are left through the leaf (a). 

 In the most curious and interesting Hydrogeton fenes- 

 tralis (fig. 52.), an aquatic of Madagascar, the paren- 



