THE LEAVES OF VASCULAR PLANTS. 29^5 



the appearance is modified by very slight difFerenees. 

 Thus, for example, when two penninerved leaves are 

 exactly opposite, and in crossing pairs, they are so 

 folded as to embrace the inner pair : we see this in the 

 Privet. These kinds of leaves are said to be Equitative. 

 When the opposite position of leaves is less exact, one 

 of the sides of each leaf is found a little on the outside, 

 and the other, consequently, a little on the inside : this 

 happens in Saponaria, and then the leaves are said to 

 be Semi-embracing. When the leaves are alternate 

 or quincunx, each is folded wholly upon itself, and, thus 

 folded, they are found lying side by side without em- 

 bracing each other : this is the case in the Beech ; they 

 are then said to be Conduplicate. 



Palminerved leaves may be considered, as we have 

 seen above, as formed by the junction of partial penni- 

 nerved limbs, each of which has a tendency to be folded 

 upon itself, and it results that the whole of the limb is 

 folded upon the nerves like a fan ; this takes place in the 

 Vine and all palminerved leaves. They are said to be 

 Plicate, or folded in a fan-like manner. 



The leaflets of palmate leaves present the same dis- 

 position : they are folded upon their middle nerve, and 

 placed side by side ; those of pinnate ones are also 

 folded and placed in like manner, covering each other on 

 the edges of a common petiole. 



Some penninerved leaves present peculiarities which, 

 without differing much from the general rule, have 

 caused them to have particular names. Thus, there 

 are some, which, although folded upon the middle nerve, 

 have their two edges more or less rolled, either outwards, 

 as in the Rosemary, and are said to be Revolute ; or 

 inwards, as in Euonyvius, or Nymphcea, which are said 

 to be Involute ; or upon one another, as in the Apricot, 

 when they are termed Supervolute. It is not known 



