SECT. I 



MORPHOLOGY 



33 



whether lanceolate, elliptical, ovate, or otherwise shaped, the flat leaf- 

 blade is distinct from the leaf-base, while a leaf-stalk may also be 

 interpolated between them (Figs. 33, 36 s). If no leaf-stalk is de- 

 veloped the leaf is said to be sessile, otherwise it is described as 



STALKED. 



Sessile leaves usually clasp the stem by a broad base. Where, as in the case 

 of the Poppy [Papaver somniferum), the leaf-base surrounds the stem, the leaves 

 are descri})ed as amplexicaul ; if, 

 as in species of Bupleurum, it com- 

 pletely surrounds the stem, the 

 term teufoliate is used. If the 

 bases of two opposite leaves are 

 united, as in the Honeysuckle 

 {Lonicera Gaprifolium), they are 

 said to be connate. Where the 

 blade of the leaf continues down- 

 wards along the stem, as in the 

 winged stems of the common Mul- 

 lein {Verbascum thapsiforme), the 

 leaves are distinguished as decuu- 

 iiENT. The petiole of a leaf merges 

 either directly into the leaf-base, 

 or it swells at its lower end into a 

 LEAB'-CUSHION Or PULVINUS, and 

 is thus articulated with the leaf- 

 base. This is the case, for instance, 

 with many of the Leguminosae. 

 The leaf-blade, in turn, may be 

 either sharply marked off from the 

 petiole, or it may be prolonged so 

 that the petiole appears winged, 

 or again it may expand at its junc- 

 tion with the petiole into ear-like 

 lobes. A leaf is said to be entire 

 if the margin of the leaf-blade is 

 wholly free from indentations, or 

 if the latter are very shallow (Fig. 

 36 sp). When the incisions are 

 deeper, but do not extend half-way 

 to the middle of the leaf-blade, a 

 leaf is distinguished as lobed ; 

 when they reach more than half- 

 way, as CLEFT (Fig. 37 sh) ; if the 

 incisions are still deeper the leaf is 

 said to be PAP.TrrE (Fig. 38 I), and 

 if they penetrate to the midrib or 

 base of the leaf-blade it is termed 



DIVIDED. The divisions of the leaf-blade are said to be pinnate or palmate, accord- 

 ing as the incisions run towards the midrib or towards the base of the leaf-blade. 

 Where the divisions of the leaf-blade are distinct and have a sepai'ate insertion on 



i D 



Fig. 34. — Lily of the Valley (Convallaria majalif:). nd, 

 Scale leaves ; lb, foliage leaves ; lib, bracts ; h, flower ; 

 ws, rhizome ; aio, adventitious I'oots. (Somewhat 

 reduced.) 



