The genus Cinnamomum

Botany and Crop Improvement of Cinnamon and Cassia 49
same type of embryo sac development in C. camphora. A more detailed embryological
study was carried out by Sastri (1958) on C. zeylanicum (C. verum) and C. iners. The
following discussion is mainly based on the above studies.
Ontogeny of the carpel
Carpellary primordium arises as a small conical protuberance on the thalamus, which
becomes cup shaped due to differential growth. One side of the cup continues to grow
and form the style and the stigma, from the other side the ovule primordium arises in
the subterminal position as a lateral protuberance.
Ovule
The ovule soon becomes bent as a result of the funiculus and comes to lie in a position
facing away from the style at the megaspore mother cell stage. The curvature of the
ovule continues further, the rate of growth varying from species to species. In C. verum
the curvature is arrested early, and at the mature embryosac stage the ovule takes a
transverse position in relation to the micropyle at right angles to the style, pointing
towards the lateral wall of the gynoecium. In C. iners at the megaspore tetrad stage or
even earlier, the tip of the ovule is at a right angle to the style. At the four nucleate
stage the curvature is complete, and the micropyle points to the style. The ovule is
anatropous, pendulous, crassinucellate and bitegmic (Fig. 2.14). Integument initials are
seen in the young ovule at the primary archesporium stage. Integuments are not very
well developed at the megaspore mother cell stage, but are fully formed at the tetrad
stage. The inner integument is three to four layered, while the outer integument is four
to five layered.
1 2 3 4
5 6 7
Figure 2.14 Ovule development in Cinnamomum. 1–3. L.S. of carpel showing successive stages in the
development of ovule. 4. L.S. of nucellus showing multi-cellular archesporium. 5. L.S.
of ovule showing megaspore mother cell. 6. L.S. of young ovule showing linear tetrad of
megaspores. 7. L.S. of ovule showing linear tetrad of megaspores of which the micropylar
three are degenerating. (Source: Sastri, 1958.)