BOTANY AS APPLIED TO VETERINARY SCIENCE. 387 
small membranous sacs, attached to each other, or united by 
an intermediate body. They vary much in form. When 
they grow together by their margins they are called synge- 
nesious. Within the anther we have a yellow-looking 
powder, called pollen , which, when examined by the micro¬ 
scope, is found to consist of grains of definite size and shape, 
and which are uniform in the same plant. Their colour is 
generally yellow, but in some plants this is blue, red, &c. 
Pollen is the organic matter by which impregnation is pro¬ 
duced in the vegetable kingdom. 
It is very important to bear in mind the position of the 
stamens, as upon this the subdivisions of exogenous plants 
in part depend. When the stamens are attached below the 
ovary they are said to be hypogynous ; if to the sides of the 
calyx, perigynous; if to the corolla, epipetalous; if on the top 
of the ovary, epigynous. 
The pistil (fig. 3, c) occupies the centre of the flower, 
being surrounded by the stamens and floral envelopes. It is 
the female organ of flowering plants. It consists of three 
parts (fig. 4), viz., style (a), stigma ( b ), and 
ovary (c). The style is the part which con¬ 
nects the ovary and stigma. It is not always 
present. When absent the stigma is sessile. 
The ovary is situated at the base, and con¬ 
tains the ovules or rudimentary seeds. 
The stigma is the enlarged upper extremity of 
the pistil. Its use is to receive the pollen 
grains from the anther, which are then con¬ 
veyed down the style to the ovary, to impreg¬ 
nate the ovules contained in it. 
The above description of parts entering 
into the formation of a flower, although very 
short and imperfect, will, I think, be sufficient 
to make the following subdivisions of the 
Natural system understood. Of the three primary divisions, 
viz., exogens, endogens, and acrogens, the former only will 
be described as having subclasses, as,according to De Candolle, 
endogens are all included in a single group of orders. Acro¬ 
gens are destitute of flowers. 
Dr. Lindley, adopting the arrangement of De Candolle, 
divides exogens into the following subdivisions. 
Subclass 1 . Thalamiflorve. —Flowers furnished with both a 
calyx and corolla, the latter consisting of distinct petals. 
Stamens always hypogynous, or united to the sides of the 
ovary. 
Subclass 2. Calycijlorve. —Flowers furnished with both a 
