80 MORPHOLOGICAL BOTANY. 



SUMMARY. 



The leaf is that part of a plant, which is always developed laterally on 

 the stem and is usually of a flattened nature. 



The base of the leaf is its organically lower end. 



The apex of the leaf is its organically upper end. 



The body of the leaf is the portion lying between the base and the apex. 



The leaf is said to be coriaceous when its texture is tough and leathery. 



The leaf is said to be lierbaceous when its texture is weak and soft. 



The leaf is said to be succulent when its texture is thick and juicy. 



The leaf is said to be membranous when its texture is thin and flexible. 



The leaf is said to be annual when it dies the same year in which it is 

 developed. 



The leaf is said to be biennial when it dies the second year. 



The leaf is said to be perennial when it lives for many years. 



The aerial leaf is one which exists exposed to the air. 



The aquatic leaf is one which exists submersed in water. 



The subterranean leaf is one which exists buried in the soil. 



The foliage leaf is one which is always green, mostly flattened, and does 

 not produce reproductive organs. 



The modified leaf is one which differs from the foliage leaf. 



The lamina is that part of a foliage leaf, which is usually expanded and 

 situated above other portions. 



The petiole is that portion of a foliage leaf, which stands between the 

 lamina and the leaf -sheath and is usually semicylindrical. 



The leaf-sheath is that portion of a foliage leaf, which stands below the 

 petiole and embraces the stem more or less assuming a tubular or sheath- 

 like form. 



Stipules are small leafy appendages situated one on each side of the leaf 

 sheath. 



Veins are the woody thread-like structures in the lamina. 



The venation is the mode of veining. 



Ribs are large veins proceeding from the base to the apex of a lamina. 



The midrib is the most prominent central rib. 



When veins are distributed to form a kind of network, the venation is 

 said to be netted-veined. 



When veins are distributed paralled to one another, the venation is said 

 to be parallel-veined. 



When the netted-veined lamina has but one central rib, the venation is 

 said to be pinnately veined. 



