Pharmaceutical botany - Lighthouse Survival Blog
Pharmaceutical botany - Lighthouse Survival Blog
Pharmaceutical botany - Lighthouse Survival Blog
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46 PHARMACEUTICAL BOTANY<br />
vular openings. The pollen is usually a powdery substance which<br />
shows under the microscope distinct grains of characteristic forms, sizes<br />
and markings. Like starch grains, each represents a particular source,<br />
hence the variety that may be examined is limited only by the number<br />
of kinds of flowers available for the purpose. In order to study pollen<br />
grains, take up by means of forceps a stamen whose anther is just de-<br />
hiscing, or letting free its contents, and tap upon a sheet of white paper;<br />
then examine with a Compound Microscope.<br />
The following are some of the forms of pollen grains:<br />
Four Spore Daughter cells hanging together as in the Cat Tail<br />
forming a pollen grain.<br />
Elongated simple pollen grains as in Zostera.<br />
Dumb-bell shaped as the pollen of the Pines.<br />
Triangular, as in the Mexican Primrose.<br />
EcHiNATE. as in the Malvaceae.<br />
Spherical, as in Geranium.<br />
Lens shaped as in the Lily.<br />
The Gynoecium, or Pistil System.—The Carpel or megasporophyll<br />
is the female organ of reproduction of flowering plants. In the Spruce,<br />
Pine, etc., it consists of an open leaf or scale which bears but does not<br />
enclose the ovules. In angiosperms it forms a closed sac which envelops<br />
and protects the ovules, and when complete is composed of three parts,<br />
the ovary or hollow portion at the base enclosing the ovules or rudimen-<br />
tary seeds, the stigma or apical portion which receives the pollen grains,<br />
and the style, or connective which unites these two. The last is non-<br />
essential and when wanting the stigma is called sessile. The carpel<br />
clearly shows its relations to the leaf, though greatly changed in form.<br />
The lower portion of a leaf, when folded lengthwise with the margins<br />
incurved, represents the ovary; the unfolded surface upon which the<br />
ovules are borne is the placenta, a prolongation of the tip of the leaf, the<br />
stigma, and the narrow intermediate portion, the style. A leaf thus<br />
transformed into an ovule-bearing organ is called a carpel. The carpels<br />
of the Columbine and Pea are made up of single carpels. In the latter<br />
the young peas occupy a double row along one of the sutures (seams) of<br />
the pod. This portion corresponds to the infolded edge of the leaf, and<br />
the pod splits open along this line, called the ventral suture.<br />
Dehiscence, or the natural opening of the carpel to let free the con-<br />
tained seeds, takes place also along the line which corresponds to the<br />
mid-rib of the leaf, the dorsal suture.