120 



ELEMENTS OF STRUCTURAL BOTANY. 



the sub-division is continued through another stage, the 

 leaf is thrice-pinnate, and so on. Sometimes, as in the 

 leaves of the Tomato, very small leaflets are found "between 

 the larger ones, and this form is 

 described as interruptedly pinnate 

 (Fig. 168). 



In the palmate or digitate forms 

 the leaflets spread out from the end 

 of the petiole, and, in describing 

 them, it is usual to mention the 

 number of divisions. If there are 

 three, the leaf is tri-foliolate ; if there 

 are five, it is quinque-foliolate. 



181. In the examination of the 

 Mallow we found a couple of small 

 leaf-like attachments on the petiole 

 of each leaf, just at the junction 



Fig. 168. 



with the stem. To these the name 

 stipules was given. Leaves which 

 have not these appendages are 



182. Besides the characters of 

 leaves mentioned above, there re- 

 main a few others to be noticed. 

 With regard to their surface, 

 leaves present every gradation from 

 perfect smoothness, as in Winter- 

 green, to extreme roughness or 

 woolliness, as in the Mullein. If hairs are entirely absent, 



Fig. 169. 



Fig. 168. Interruptedly pinnate leaf. 

 Fig. 169. Leaf of Pitcher-Plant. 



