Page 4 - Pharmacognosy-I (02-06-06-102)
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Medicinal leaves
Leaf
Definition:
The leaf may be defined as a lateral outgrowth on the stem.
A complete leaf is composed of three parts:
• Lamina or Blade.
• Petiole or Stalk.
• Base: It is the part of the leaf by which it is attached to the
stem and is slightly enlarged.
Duration of leaves:
The leaf is described as:
• Persistent: when live for one year or more, thus the plant is
described as evergreen.
• Deciduous: when falling in autumn, thus the plant bears no
expanded leaves during winter.
Petiole or leaf-stalk:
It serves to carry the lamina away from the stem and conducts
materials to and from the lamina. When it is present, the leaf is
described as petiolate, while when absent, it is sessile.
The lamina:
It may be:
• Simple: Consists of a continuous, undivided surface
• Lobed or divided: cut up into a number of lobes, connected
together by an undivided portion.
• Compound: Completely segmented into a number of separate
leaflets.
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