22 LEAVES, PLOWEES, AND FRUIT 



have compound leaves (Plate III, Fig. P; Plate III, 

 Fig. R). 



At the base of the blade of simple leaves there are in a 

 few cases a pair of blade-like parts at the side of the leaf 

 stalk, which are called stipules. Of the common shrubs 

 the one showing these most conspicuously is the so-called 

 Japan quince. Books make much of stipules, in the 

 text, but they are so rarely seen, except in the earliest 

 spring, that I have left them almost entirely out of con- 

 sideration in the keys and the descriptions. All oaks are 

 said to have stipules, but they are so short-lived that none 

 are to be found when the leaves have fully expanded. 



There are two distinct plans for the arrangement of the 

 blades on compound leaves. They are either all together 

 at the end of the leaf stalk, as in the red clover with 

 3 blades, or in the horse chestnut with 7 blades, these 

 are called palmately compound (Plate IV, Fig. X) ; or 

 they are regularly arranged along the stalk as in the elder 

 and common sumach, these are called pinnately compound 

 (Plate III, Fig. P). 



The pinnately compound leaf may have an even num- 

 ber of blades, there being no blade at the tip ; in this 

 case it is called evenly or abruptly pinnate (Plate IV, 

 Fig. S). More frequently there is an odd blade 

 at the end, and the leaves are odd pinnate (Plate III, 

 Fig. Q). 



Both palmate and pinnate leaves may be the second or 

 third time divided before the blades are reached ; in such 

 cases they are twice (bi) or thrice (tri) palmate or pin- 

 nate as the case may be. The mimosa (Plate IV, Fig. S) 

 is twice or bipinnate, and the astilbe (Fig. 239) is three 

 times or tripalmate. The honey locust is curious ; many 

 of its leaves are once pinnate, while those on the rapidly 

 growing twigs are bipinnate. Both the mimosa and* the 

 honey locust lack end blades and are abruptly pinnate. 



As far as the classification of leaves has been given, it 

 can be summed up in the following : 



