64 DESCRIPTIVE BOTANY. PART 1. 



The intimate relation which subsists between simple 

 and compound leaves, is well exemplified in some 

 cases, where two or more contiguous leaflets become 

 grafted together, and thus reduce the usual extent of 

 the subdivision to a lower degree. This may be often 

 seen in some species of Gleditsia (fig. 57-), where dif- 



ferent parts of the same leaf assume a simply, doubly, or 

 triply compound character. It is difficult in some cases 

 to decide whether a leaf should be considered compound, 

 or simple ; and it is usual to account all leaflets which 

 are articulated to the petiole, as parts of a compound 

 leaf, even though they may be reduced to one in num- 

 ber, as in the case of the orange ; but those which are 

 not articulated, even though they may be otherwise dis- 

 tinctly formed, are considered as subdivisions only of a 

 simple leaf. Where these articulations exist, each 

 leaflet falls separately from the main petiole, when 

 this also becomes detached from the stem ; but where 

 the leaflets are not articulated to the petiole, the limb 

 falls entire, with the petiole attached. 



(b.) Palminerved. Instead of forming a midrib, the 



