FLOWERS 129 
119. Symmetry of the flower. Except in a comparatively 
small number of cases (of which the familiar canna, or Indian 
shot, is a good example) the perianth usually shows some 
kind of symmetry. Either (as in fig. 102) the parts are ar- 
ranged in a radial fashion, like the points of a star, or else 
they have corresponding halves , 
in one plane to the right and 
left of an axial line, as in pan- 
sies and violets (fig. 106), in the 
most familiar flowers of the Pea 
family, and in those of the Mint 
family. Flowers with radial 
symmetry are said to be actino- 
morphic, and those with corre- 
sponding halves are said to 
have bilateral symmetry, or to 
be zygomorphie. 
Sometimes, as in the Milk- 
weed family, the corolla has 
extraordinary forms which fa- Fie. 108. Diagrams to show struc- 
cilitate seed production by the hanover 0 gates 
aid of insect visitors (fig. 134). 2 vOUNEe? Hage, Wath four: cham 
ers, or locules (loc), containing pollen 
120. Parts of the stamen; mother cells dividing to form pollen 
union of stamens. Many stamens grains; B, an older stage, in which the 
nese : pollen grains (p) are fully formed and 
have a form similar to thatshown each pair of locules is uniting to form a 
in figure 107, 4, consisting of a nase ee ee a. om i an) . 
rather slender stalk (the filament) Ses Galligvie att ee 
which bears a stouter structure, 
the anther. Anthers which have no filaments are said to be 
sessile. Within the anther the stamen produces a powdery or 
pasty substance known as pollen, which, when magnified, is 
seen to consist of minute grains (fig. 117). These differ 
greatly in form and markings in different families of plants. 
The mode of origin of the pollen sacs in which pollen is pro- 
duced is partially shown in figure 108. When the sacs are 
fully mature, they open and allow their contents to escape. 
loc: * 
