44 PINNATE LEAF [CH. 



or multi-foliolate, &c. ; nor need the numbers be odd. A 

 peculiar case is that of the uni-foliolate leaves of the 

 Barberries and Oranges where one leaflet is attached by 

 a distinct articulation to the petiole : each is therefore a 

 compound leaf, but with only one leaflet. 



In pinnate leaves, again, we may have tri-, quinque-, and 

 multi-foliolate leaves, where one leaflet is odd and 

 terminal; such leaves are termed impari-pinnate, e.g. 

 Robinia. If the numbers are paired, and there is no 

 odd terminal leaflet, the leaf is pari-pinnate, though such 

 leaves do not occur among those here to be dealt with. 



The case of the tri-foliolate leaf e.g. Laburnum, 

 Broom, &c. requires careful examination. That it is 

 a pinnate leaf is determined by the separate articulation 

 to a slight stalk of the terminal leaflet ; but it is easy for 

 the student to be tempted to regard the whole leaf as 

 of the palmate type if this point be overlooked. 



It must not be supposed that the distinctions between 

 simple lobed leaves and compound leaves are absolute, 

 since plenty of examples can be selected where the upper 

 part of a leaf is pinnatifid and the lower pinnate, e.g. in 

 Pyrus Aria, Agrimony and other Rosaceae, which only 

 serves to emphasize the fact that the degree of segmenta- 

 tion of the leaf merely expresses the extent of its 

 branching. 



In the following examples it should be understood 

 that the average type of the leaf is referred to ; com- 

 parison of numerous leaves will show that considerable 

 variation in contour and in details may be met with on 

 one and the same plant, examples of which are very 

 conspicuous in the Blackberry, White Poplar, Pyrus 

 Aria, Fig, and Mulberry. 



The leaves in the following are compound and 

 pinnate : 



