Leaves with stipules are called stipulate . The leaves without stipules are called exstipulate or estipulate . The stipules are commonly found in dicotyledons. In some grasses (Monocots) an additional out growth is present between leaf base and lamina.
It is called Ligule. Sometimes, small stipule like outgrowths are found at the base of leaflets of a compound leaf. They are called stipels. The main function of the stipule is to protect the leaf in the bud condition.
. . Venation The arrangement of veins and veinlets on the leaf blade or lamina is called venation. Internally, the vein contains vascular tissues.
Conventionally venation is classified into two types namely, Reticulate venation and Parallel venation. I. Reticulate venation In this type of venation leaf contain a prominent midrib from which several secondary veins arise that branch and anastomose like a network. This type of venation is common in all dicot leaves.
It is of two types. . Pinnately reticulate venation (unicostate): In this type of venation there is only one midrib in the centre which forms many lateral branches to form a network. Example: Mangifera indica.
. Palmately reticulate venation (multicostate): In this type of venation there are two or more principal veins arising from a single point and they proceed (c) Cinnamomum (a) Ficus (b) Cucurbita Figure . : Types of reticulate venation (a) Pinnately reticulate (b) Palmately reticulate (Divergent) (c) Palmately reticulate (Convergent) . .
Phyllotaxy The mode of arrangement of leaves on the stem is known as phyllotaxy (Gk. Phyllon = leaf ; taxis = arrangement ) . Phyllotaxy is to avoid over crowding of leaves and expose the leaves maximum to the sunlight for photosynthesis. The four main types of phyllotaxy are ( ) Alternate ( ) Opposite ( ) Ternate ( ) Whorled.
. Alternate phyllotaxy In this type there is only one leaf per node and the leaves on the successive nodes are arranged alternate to each other. Spiral arrangement of leaves show vertical rows are called orthostichies . They are of two types.
a) Alternate spiral: In which the leaves are arranged alternatively in