THE LEAF 



31 



CHAPTER VII 



THE LEAF 



Leaves are lateral appendages of the stem, and grow 

 in an acropetal order. The leaves of the embryo are 

 known as cotyledons, the leaves of the underground 

 stem as scales, the ordinary green leaves ^ 



of the aerial stem as foliage or vegeta- 

 tive leaves, and the leaves of the flower, 

 such as petals, &c., as floral or repro- 

 ductive leaves. In this chapter we shall 

 deal with foliage leaves only, and these 

 latter are what we commonly call leaves. 



A typical leaf consists of a flat broad 

 portion, the blade or lamina, situated 

 at the top of a thin elongated portion, 

 the PETIOLE or stalk, the base of which 

 broadens out into a sheath, which 

 partially or wholly embraces the stem. 

 Take, for instance, a Plantain leaf (fig. 

 27). It has a large oblong blade, a 

 long^ petiole, and a long, broad, con- 

 cave sheath, the ^sheaths of the leaves 

 collectively forming the so-called stem 

 of the plant. Most of the Monocoty- 

 ledons have leaves with sheathing bases, 

 as, for example, Palms (tal, narikel, 

 khejur, supari, &c.). Grasses (bans or Bamboos, akh 

 or Sugar-cane, bhutta or Maize, durba, &c.), Arums 

 (kachu, man-kachu, &c,). Ginger, Turmeric, &c. 

 Among Dicotyledons most of the UmbelUfertx, such 

 as dhania or Coriander (Coriandrum safiviim), mouri 

 or Fennel {Fcemcwlum viUgare), juan {Carum cop- 



Fig^. 27. — Plantain 

 Leaf: Kala pata 



a. Sheath. 

 b. Petiole, c. Blade. 



