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1. Structure of Ovule & Types of ovule

2. Structure of ovule
Ovule is the fertile part of Pistil.
Morphologically it is called
megasporangium. The ovule consists
of the stalk and the body. It is
protective outer coat are called
integuments and the stalk called
funicle. The ovule may have either
one or two integuments. Ovule with
one integuments are called unitegmic
ovules and those have with two
integument are bitegmic. The
integuments envelops the inner
nucellus except at one place which is
the opening known as micropyle. This
micropyle is the main passage area
for the entry of pollen tube. Nucellus
is the fertile part that form the
female gametophyte (embryo sac).
Basal region of the ovule is called
chalaza.

3. • Following are the conditions seen in ovule in relation to
integuments :
(i) Unitegmic : Ovule with a single integument, e.g.,
sympetalous or gamopetalous dicotyledons.
(ii) Bitegmic : Ovule with two integuments as in
polypetalous (Archichlamydeae) dicotyledons and
monocotyledons.
(iii) Caruncle : It is formed as an outgrowth of the outer
integument in the micropylar region. Caruncle is common
in the ovules of Euphorbiaceae. e.g., Castor (Ricinus).
(iv) Aril : In Asphodelus, a 3rd integuments called aril.
Arises from the base of ovule & its covers complete the
other two integument.
(v) Ategmic : In some parasites like Loranthus, Viscum,
Santalum etc., there is no integument. Such an ovule is
called ategmic.

4. Types of Ovules
• Based on the position of micropyle and
chalaza with respect to funicle, the ovule
are of following six types.
• a) Orthotropous
• b) Anatropous
• c) Hemi-anatropous
• d) Campylotropous
• e) Amphitropous
• f) Circinotropous

5. 1. Orthotropous
• The micropyle, chalaza and funicle are
in straight line. This is most primitive type
of ovules. e.g., Betel, Piper, Polygonum.

6. 2. Anatropous
• The body of the ovule is completely inverted
(turn at 180o angle ) so that micropyle and
funicle come to lie very close to each other. e.g.,
82% of angiosperm families.

7. 3. Hemi-anatropous
• Ovule turns at 90 angle upon the funicle or body of
ovule is at right angle to the funicle e.g., Ranunculus.

8. 4. Campylotropous
• Ovule is circled more or less at right angle to
funicle. Micropylar end is bent down slightly. e.g.,
in members of Leguminosae and Cruciferae.

9. 5. Amphitropous
• The body of the ovule is very much curved
and embryo sac becomes curved like horse shoe
e.g. Lemna, Poppy,

10. 6 Circinotropous
• The funicle in this case is especially long that it
creates a nearly full circle around the ovule and
micropyle is ultimately pointing upwards.

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