26 



directly, also develop branches on which the leaflets arise, these 

 secondary branches are termed pinnules and the leaf is said 

 to be tn-pinnate, as are often the leaves of Moringa pterygosperma. 

 A compound leaf is usually described by the number of leaflets, 

 thus J}i~, tri-, quadri-foliolate and so on. 



It is not always easy at first sight to distinguish between 

 a pinnately-and palmately-trifoliolate leaf, but on close in- 

 spection it will be seen that in the former the leaflets do not 

 all spring from the same point see the pinnately 3-foliolate 

 leaf of Desmodium tilicefolium, Fig. 1, Plate F, in which an 

 obvious rhachis extends from the point of insertion of the 

 pair of lateral leaflets to that of the terminal leaflet. The 

 junction between the rhachis and the base of the terminal 

 leaflet, or of its petiolule, is often marked by a distinct joint 

 or articulation ; sometimes also the petiolule of the terminal 

 leaflet is swollen and is thus easily distinguished from the 

 rhachis. The leaf of Desmodium tiliaefolium may be compared 

 with the palmately 5-foliolate leaf of Holboellia latifolia in 

 which all the leaflets spring from a distinct joint at the apex of 

 the petiole, Fig. 2, Plate V. 



It is not always easy to at once decide whether foliar 

 structures are leaves or leaflets. If we look at a branch of 

 Phyllanthus Emblica we find the small leaves arranged in two 

 ranks along the twigs giving the latter the appearance of 

 pinnate leaves. Minute buds may, however, be often found 

 in the axils of these small leaves, thus indicating that they 

 are true leaves, no buds being normally produced in the angle 

 between a leaflet and the axis from which it springs. Moreover 

 flowers are found on these leaf-bearing twigs thus showing that 

 the latter aje branches of the stem and not petioles, rhachises, 

 or branches of them, on which no flowers normally arise. 



A leaf which is at first palmately 3-nerved but in which 

 each of the lateral nerves is forked, the outer branch of each 

 fork sometimes again forking, is said to be pedately -nerved. 

 Such a leaf may be lobed, cleft, parted, divided or compound, 

 just as is the case with an ordinary palminerved leaf, and in 

 the last case we get a pedately -compound leaf, which is usually 

 simply called a pedate leaf. See Fig. 7, Plate IV. 



The principal terms which are usually employed for 

 describing the general shape of leaves have now been 

 enumerated above, but it must be remembered that the forms 

 of leaves are infinitely various and that it is neither possible 

 nor desirable to have separate names and definitions for every 

 form that may be met with. Here, as elsewhere, morphology 



