46 THE AMERICAN BOTANIST. 



an example of a compound leaf, part of which has chant^ed 

 to a tendril while the part nearest the stem still functions 

 as a foliage leaf. The bracts, mentioned in a previous 

 article are also considered to be of leafy origin. 



VERNATION AND VENATION. 



These two words so much alike in spelling are far 

 apart in meaning. The first refers to the wa}- the new 

 foliage leaves are packed in the bud. When folded like a 

 fan (in the maple, for example) the3' are plicate; when 

 rolled up from one margin to the other they are convolute, 

 and when the two margins are rolled up to the mid -rib 

 they are involute. Revolute indicates that the leaf-mar- 

 gins are rolled backward toward the middle of the under 

 surface. 



Venation has reference to the wa}' the wood}- tissues 

 or veins are distributed through the leaf. If all the main 

 veins extend from base to apex or from midrib to margin 

 at equal distances apart they are parallel veined ; if there 

 are several main veins in the leaf and these give off smaller 

 veins that again divide and connect with the veinlets of 

 other veins, they are said to be reticulated or net- veined. 

 The net-veined leaves are further distinguished as being 

 pinnately veined or palniately veined. In the first there is 

 a strong midrib reaching from base to apex and this gives 

 off veins that go to the margin ; in the second, several of 

 the basal veins are nearly as strong as the midrib and ex- 

 tending through the leaf give off veins. An excellent illus- 

 tration is found in the maple. 



POSITION ON THE STEM. 



Anyone who examines a stem will notice that the 

 leaves are not arranged akmgit hap-hazard but that they 

 grow from definite regions called joints. Thus in some 

 plants with two leaves at each joint they are opposite on 

 the stem, in others there is but one leaf at a joint and the 

 leaves are alternate, while in still others there maj' be a 

 circle of leaves at the joint in which case they are whorled. 

 When these opposite leaves are sessile, that is, without a 

 petiole, their bases often grow together and the two leaves 



