Vlll 
be unsymmetrical. The petals are often very different in form and 
size, and the flower then becomes irregular, as in the Snapdragon, 
Foxglove, and Monkshood. One peculiar form of irregular flower 
prevalent in the Leguminosse or Pea tribe is known as papilionaceous, 
from a fancied resemblance of the petals to a butterfly with its 
wings expanded. The upper of the five petals, usually larger than 
the rest, termed the vexillum , is somewhat curved backwards; the 
two lateral ones are called alee or wings; while the two lower, which 
are united slightly by their margins, are styled the carina , or keel. 
Attached to the petals, or between them and the stamens, are 
sometimes found small processes of various form, to which the 
name of nectaries is usually given. 
The stamens are arranged within the petals, in one or more 
whorls. They consist generally of a long slender column or 
filament bearing a small body at the apex called the anther , 
which contains the pollen or powdery matter by which the seed 
is fertilized. This anther is usually two-celled, but sometimes 
one-celled, and the manner in which the cells open to discharge 
their pollen is often a most important character in distinguishing 
plants. The stamens are sometimes united by their filaments into 
a column with the pistil, or into several groups, and in some plants 
the anthers are similarly connected. The anther is the only 
essential part of the stamen, the filament being often wanting. 
The pistil is the body through which the fertilization of the seed 
takes place. There is sometimes only one, and sometimes many; 
they always occupy the centre of the flower. A pistil generally 
consists of a club-shaped or variously divided process called the 
stigma, supported on a column termed the style, by which it com¬ 
municates with the ovary or embryo seed-vessel at its base; the 
style, however, is often absent. 
Like all other parts of the flower, the ovary is formed of modified 
leaves variously arranged. Sometimes it consists of one leaf with 
the margins united so as to form a vessel in which the seeds are 
