Herbs are defined as non-woody plants that die down to the ground after flowering. They may consist of aerial parts like stems, leaves, and flowers. Herbs are classified based on their life duration as annual, biennial, or perennial. The stem is the main axis that supports leaves and other plant organs. Its functions include transport, support, and storage. Stem characteristics include shape, type (herbaceous, succulent, woody), surface features, branching patterns, and internal structure visible microscopically. Medically important herbs include Lobelia, Hyoscyamus, Mentha, and others containing volatile oils, alkaloids, or other compounds.

2. Herbs
• Definition:
• The herb is a plant whose stem doesn’t become
woody and permanent but dies down to the
ground after producing the fruits and seeds.

3. HERBS ( Herba )
What is Herb?
In Pharmacognosy
Herb is a drug composed
usually of the tender
parts of the plant axis.
(the stem + leaves +flowers + fruits).

4. • It may consist of:
• 1- part of the aerial shoot usually the tops.
• 2- The whole aerial part of the plant as Lobelia.
• 3- Occasionally the whole plant including the
roots.
• 4- The whole undifferential plant body or thallus
of the lower plants of thallophyta.
• The main axis of the herb consists almost entirely
of stem, the root or other underground structure
only rarely being present.

5. Herbs are classified according to life duration into
Biennial
Herbs live two
seasons and dies.
e.g: Digitalis and
Sugar beet.
Perennial
Plants live more
than two years.
e.g: Belladonna &
Citrus.
Annual
Herbs live one
season and dies.
e.g: Stramonium
and Umbeliferous
herbs

6. Definition:
Stem: - It is a part of the plant which carries the
leaves and other plant organs.
- It has nodes and internodes.

7. Stemfunction
1-Plant support
2-Carries leaves
and flowers, etc…..
3-Conduct water and
minerals from the root
to the leaves.
4-Conduct photosynthesis
products from leaves to the
root or other organs.

8. Macroscopical
Characters
1-Shape
2-Kinds of the stem
3-Surface of the stem
4-Fracture
5-Direction of growth
6-Branching of the stem

9. Shape of The Stem
Cylindrical
Triangular
Flattened
or
compressed
Winged
e.g.
Lobelia
Ribbed
or
with furrows
Quadrangular
e. g. Mentha
Angular
Pentagonal
Twisted

10. The aerial stem according to the nature and
texture has several types which are:
• 1- Herbaceous stem:
• is a plant that has leaves
and stems that die down at the
end of the growing season to
the soil level. They have no
persistent woody stem above
ground.
• Herbaceous plants may be
annuals, biennials or
perennials.
Kinds of The Stem

11. • 2- Succulent stem:
• A succulent plant or
succulent is a plant that
has fleshy and turgid
water-storing tissues
such as stems, leaves or
roots, capable of
retaining large amounts
of moisture (usually as
a drought survival
strategy).

12. • 3- Woody stem:
• A woody plant is a plant that produces wood as
its structural tissue. Woody plants are usually
either trees or shrubs. These are usually
perennial plants whose stems and larger roots
are reinforced with wood produced from
secondary xylem.

13. • 4- Creeping stem:
• a plant whose stems spread along the ground and
root by means of adventitious roots.
• Creepingstems with short internodes are called
runners, and those with long internodes are called
stolons.

15. • 5- Sucker stem:

16. • 6- Climbing stem:
- When the stem is weak
and attaches itself to a
support which is a
neighborhood plant by
means of tendrils,
prickles or hooks or
adventitious roots.
- e.g: Pepper.

17. • 7- Twining:
- When the stem attaches
itself to support by winding
around it in this case the
stem is usually thin, long
with far internodes.
- e.g.: Convulvulus & Vine.

18. Branching of the stem
1- Dichotomous
(or Apical) branching
The main growing point
is divided into 2 equal
halves. e.g. Thallophyta
(Ergot)
2- Axillary branching
When the branch arise
from the lateral axillary
buds of the leaves.
a) Monopodial
branching
b) Sympodial
branching

19. a) Monopodial branching:
The main stem axis continues
growing from the apical
growing point. The lateral
branches never exceed the
length of the main axis.
b) Sympodial branching:
The apical growing point of
the main axis stop to grow and
one or more of lateral axillary
buds continue the growth. The
lateral branches exceed the
main axis in length.

20. Examination of the Stem
• 1- Macroscopical characters:
- Condition:
- Shape
- Colour
- Nodes and internodes
- Phyllotaxis
- Surface
- Fracture
- Odour
- Taste

21. Microscopical
Characters

22. T. S. in Young (herbaceous) stem of Dicotyledons:
[ Vascular bundle is Open V.B. ]
Pericycle

23. Structure of The Stem
Epidermis:
with cuticle,
stomata and
hairs
Cambium: Responsible for
2ry thickening giving 2ry
phloem outside and 2ry
xylem inside.
Phloem
Xylem: Vessels ( Spiral,
annular, pitted.
Fibers and wood
parenchyma)
Endodermis:
inner most
layer of
cortex.
Pith:
parenchyma;
pitted lignified
Cortex:
Parenchyma,
Collenchyma
Pericycle:
parenchyma,
collenchyma,
fibers, sclereids.
N.B.
Stele: All tissues inside the endoderm .

24. Types of vascular bundles
Open vascular bundle Closed vascular bundle
Collateral V.B. Bicollateral V.B.
phloem
cambium
xylem
phloem
No cambium
e.g. Monocot.
Phloem
Xylem

27. T.S. in Monocot. Stem T.S. in Dicot. Stem

28. Herbs of Medicinal Importance
Lobelia
Hyoscyamus
Cannabis
Mentha
Thyme
Ergot
Ephedra
Vinca & Passiflora
Resin
Herbs Containing
Alkaloids
Herbs Containing
Volatile oil
Others

29. Medicinal Herbs
Lobelia
Hyoscyamus
Mentha
Thyme
Ergot Ephedra
Passiflora
Official Herbs Non-Official
Herbs
Cannabis
Vinca
Yeast
Fucus
Cetraria
Chondrus