58 



PART I. THE MORPHOLOGY OF PLANTS. 



[ 12. 



the pitcher begins in very much the same way as that of the lamina 

 of a peltate leaf ; but instead of remaining flat, it becomes tubular 

 by continued basal intercalary growth (see p. 17). The leaf may, 

 as in Sarracenia and Darlingtonia, be sessile ; or it may be 

 petiolate, as in Cephalotus and Nepenthes : in Nepenthes (Fig. 

 37) the petiole is winged for some distance in its lower portion. 

 The lid, when present, is a development of the apical, or sub-apical 

 (Nepenthes), portion of the lamina; at its first development it 

 adheres firmly to the rim of the ascidium, from which it eventually 

 separates, except at the point of attachment ; the lid is bilobed. 

 2. Leaf -Tendrils (see p. 49) are leaves or parts of leaves which 

 have a somewhat filamentous form, and 

 which possess the property of twisting 

 spirally round foreign bodies, thus 

 fixing the plant (see Part IV.). In 

 species of Clematis, Tropoeolum, etc., 

 this function is performed by the pe- 

 tiole of the foliage-leaf ; but in the 

 Vetches and Peas there is a division 

 of labour of this kind, that the anterior 

 leaflets of the pinnate leaf are modified 

 into tendrils (Fig. 28, C, rf) ; in La- 

 thyrus Apliaca all the leaflets undergo 

 this metamorphosis, and the special 

 functions of the foliage-leaves are dis- 

 charged by the stipules. The tendrils 

 of the C ucurbitaceae are also metamor- 

 phosed leaves. 



3. Leaf -Spines are leaves or parts of 

 leaves which are modi tied into pointed, 

 hard, woody structures. Spiny teeth 

 are often present on foliage leaves (e.g. 

 Holly, Thistles) ; in species of Caragana and Astragalus the phyl- 

 lopodium of the pinnate leaf becomes a spine after the falling-off 

 of the green leaflets ; finally, the entire leaf becomes spiny in 

 Berberis (Fig. 38). 



4. Scales or cataphyllary leaves (Fig. 36 N). These are usually 

 of a yellow or brown colour, of simple structure, without project- 

 ing veins, and are attached to the stem by a broad base. They 

 may be regarded in some cases as leaf-bases, the laminae of which 

 have not developed ; and in other cases, as entire leaves which 



FIG. 37. Pitchered leaf of Ne- 

 penthes, a Organic apex of leaf ; 

 b leaf-base ; pet petiole, winged 

 in its basal portion ; as ascidium ; 

 I its lid; fr fringe of ascidium 

 (reduced). 



