Page 98 - Pharmacognosy 2 PG303 (1)

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

Herbs
The term herb in botany is defined as a plant whose stem does not become woody and
permanent but dies after fruiting. In pharmacognosy, it indicates a drug composed of the tender
parts of plant axis, leaves, flowers, and fruits taken from annual, biennial, or perennial plants. It
consists of:

1- Flowering tops of flowering plants e.g. Cannabis.
2- The whole aerial parts of the plants e.g. Lobelia.
3- The entire plant body or thallus of lower e.g. Cetraria, Ergot, etc.

Types of Herbs
1- Annual: live for one season before seeds production then dies e.g. stramonium.
2- Biennial: live for two seasons before seeds production then dies e.g., Digitalis.
3- Perennial: live for more than two years and have perennial rootstock, which throw up
aerial shoots annually e.g. Belladona. The main axis in herbs consists almost entirely of
stems.

The stem
It may be defined as that part of the plant axis which bears leaves or modifications of leaves
at certain, usually swollen points, called nodes. The stem usually grows above the ground and is
termed aerial stem, but sometimes grows below the surface of the ground and termed subterranean.

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