UNIVERSITATIS LATVIENSIS - DSpace

On the development of pollen and embryo-
represent
sac of Papaver Rhoeas L.
By Marija
Vilcins and Karlis Abele.
The young anthers in their early stages of development
sperms. A young
the usual appearance of anther development of angio-
anther is an elevated little protuberance with
cells not yet differentiated (Fig. 3, 5). Contemporarily with the
continuation of development begins the differentiation of the
sporogenous cells. The pollen mother cells are growing larger,
forming more extensive nuclei and becoming more stained with
haematoxylin and gentiana-violett-eosin. Already in the early
stages of the anthers the development of vascular tissue can be
noticed (Fig. 6).
The sporogenous cells become gradually richer in plasma.
At the beginning of the development of the pollen
mother cells
the tapetum cells cannot be observed, later they appear
in the
form of a layer of one row of cells, that differ from the sporo-
genous cells (Fig. 7). As soon as the pollen-sack is covered
by the tapetum cells, the pollen mother cells enter the prophase
of tetrad division. The tapetum cells differ from the pollen
mother cells in their peculiar appearance
and their often remar-
kable size (20p.
—
40p.). In
many cases the tapetum
cells are
2-nucleate. The two nuclei arise from the usual mitotic division
of nucleus, but no division of cell follows the division of nuc-
leus, and the formation of the wall fails to appear.
Both the
nuclei of the 2-nucleate cells can be observed without a connec-
tion between them, but in many
cases between these nuclei can
be seen some coherence, a kind of plasma bridge, or the nuclei
may also be in connection between them forming a figure that
looks like the amitotic division of a nucleus. There is reason
to think that in these cases the nuclei flow together.
There are
also to be seen longish nuclei, that are evidently formed by the
junction of the two nuclei. Nuclei, that arise in such a manner
have two nucleoli, while the simple nuclei in other cells posses
usually only
one nucleolus.
The 2-nucleate tapetum
during the development of the pollen
the final corrosion.
cells remain in this condition also
and can be observed till
It can be added to the description of the tapetum cells,
that in the part which is nearer to the epidermis of the anther,
Acta Hortl Bot. Unlver». Latv. 11. 9