PLANT ORGANS AND ORGANISMS 
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Triangular, as in the (Enotheras. 
Echinate, as in the Malvaceae. 
Spherical, as in Geranium, Cinnamon and Sassafras. 
Lens-shaped, as in the Lily. 
Spinose, as in the Composite. 
Barrel-shaped, as in Polygala. 
Under the microscope the immature pollen grain generally consists 
of two membranes, an outer firmer one called the exospore, which 
may be variously marked and which possesses deficiencies in the 
form of “pores” or “clefts,” and an inner delicate cellulose mem¬ 
brane called the endospore, which surrounds a protoplasmic interior 
in which are imbedded a nucleus, oil droplets and frequently starch 
or protein. 
Pollinia. —These are agglutinated pollen masses which are com¬ 
mon to the Orchidacece and Asclepiadacece. 
The pollen of many plants, notably certain species of Composites, 
Graminece and Rosacece, has been shown to be responsible for “Hay 
Fever.” At the present time serums, extracts and vaccines are 
manufactured from pollen to be used in the treatment of this disease. 
The Gynoecium or Pistil System. —This is the female system of 
organs of flowering plants. It may consist of one or more modified 
leaves called carpels. Each carpel or megasporophyll is a female 
organ of reproduction. In the Spruce, Pine, etc., it consists of an 
open leaf or scale which bears but does not enclose the ovules. In 
angiosperms it forms a closed sac which envelops and protects the 
ovules, and when complete is composed of three parts, the ovary or 
hollow portion at the base enclosing the ovules or rudimentary seeds, 
the stigma' or apical portion which receives the pollen grains, and 
the style, or connective which unites these two. The last is non- 
essential and when wanting the stigma is called sessile. The carpel 
clearly shows its relations to the leaf, though greatly changed in 
form. The lower portion of a leaf, when folded lengthwise with the 
margins incurved, represents the ovary\ the infolded surface upon 
which the ovules are borne is the placenta, a prolongation of the 
tip of the leaf, the stigma, and the narrow intermediate portion, the 
style. A leaf thus transformed into an ovule-hearing organ is called 
a carpel. The carpels of the Columbine and Pea are made up of 
