Page 49 - Pharmacognosy-I (02-06-06-102)

fibrous layer. The fibrous layer appears as beaded cells in
surface view.
4- Pollen grains: The pollen constitutes the fine powder that is
liberated on the dehiscence of the anther. It is formed from
the pollen-mother cells, which fill the immature pollen sac
and each of which by division produces four pollen grains
contain oil droplets and frequently minute starch granules.
They are minute varying in shape and size but are commonly
constant for each species and constitute the most
characteristic element in powdered flower.

The pollen grain consists of wall of two membranes, an inner
membrane called intine and an outer membrane called exine, the
exine may be either smooth e.g. saffron, warty e.g. Datura or spiny
e.g. chamomile. The exine may show one, two, commonly three or
more minute thin areas or pits called germ pores from which the
pollen tube protrudes. Also, a narrow lanceolate areas or grooves
called germinal furrows may exist to accommodate the expansion
and shrinkage of the pollen grain due of humidity. The number of
germ pores and germinal furrows and characters of the surface of
the exine in addition to shape and size are usually constant and
characteristic for each species.

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