32 



MORPHOLOGY 



ticum), &c. Ranunculacece and Dilleiiiacecs (chalta) 

 have often sheathing leaves. 



The majority of the leaves, however, have only the 

 blade and the petiole, and not the sheath (fig. 28). 

 A small minority have the blade only, and neither the 

 petiole nor the sheath. 'In Grasses the leaves have 

 usually blade and sheath, but no petiole, or hardly 

 any. Leaves with petiole are called petiolate, and 



leaves without petiole 



Apex 



Leaf Blade 



Veins 



Petiole 



Midrib 



Axil 



Node 



SESSILE. In fact, the 

 word sessile is used to 

 designate all structures 

 that are not provided 

 with a stalk. Leaves 

 with a very short petiole 

 are* often described as 



SUBSESSILE or SUB- 

 PETIOLATE. It should, 



however, be remem- 

 bered that leaves that 

 have no petiole, but a 

 sheath, as those of most 

 Grasses, are not ses- 

 sile, because in such 

 cases the blades are not inserted directly on the stem, 

 as the blades of true sessile leaves are. 



A leaf-blade, which for convenience is often desig- 

 nated shortly as a leaf, should be examined with re- 

 gard to its form, margin, apex, base, venation, sur- 

 face, and consistency. The form may be described in 

 ordinary English, but it would be more convenient 

 to use the following technical terms, namely: (i) orbi- 

 cular (fig. 29) or round, as in padma {Nelumbium); 

 (2) LINEAR or long, as in most Grasses; (3) lanceo- 

 late or lance-shaped, as in Bamboo; (4) ellip- 



Fig. 28.- 



-Diagram to Illustrate Parts 

 of a Leaf 



