BVD AND LEAF. 



87 



expansion of the bark ; with two surfaces : one faeing the 

 sky, called the upper, 

 or inner face ; one 

 facing the earth, called 

 the under, or outer face. 

 The line where these 

 faces meet is the Mar- 

 gin. The Complete 

 Leaf consists of Blade 

 (lamina), Petiole (leaf- 

 stalk), and Stipule. 

 When the petiole is 

 wanting the leaf is ses- 

 sile ; jvhen the stipule 

 is wanting the leaf is 

 exstipulate. 



184. The Slade has 



a frame or hbrOUS r,g, uS.-Pltcher-Plant (iVepen/iM AsMZiatoWa). 



branches called Jtlibs 



or Nerves. The strongest, in the centre (Fig. 74), is the 

 Midrib ; those branching from it are Veins; the smaller 

 ones branching from the veins are Venules (little veins); 



and the whole make a net, 

 which gives name to neir- 

 veined leaves. Hold a leaf 

 between you and the light ; 

 its venation (veining) will 

 be beautifully seen. (Leaf- 

 pulp is treated of in Les- 

 sons XXXL, XXXII.) 



185. Transformations. — 



Though plants, as a rule, feed on 

 inorganic matter, some of them 

 have a daintier tooth, and make 

 a dessert of insects and animal 

 flesh ; using various devices to 

 ensnare their prey. The Ameri- 

 can Ply-Trap (Pig. 112) allures 

 flies by exuding a sticky sub- 

 stance from the strong gland- 

 bearing hairs on its leaf-blade; 

 as soon as the insect alights the hairs impale it, the leaf closes over it, 



Fig. 114. — Sarracenia purpurea : 1, fl., corolla 

 removed, showing the umbrella-like stigma 



o, complete fl. ; b, ovary ' ' 



Flaut entire. 



, section of same. 



