150 ELEMENTS OF BOTANY 
Study of Unisexual Flowers. — Examine, draw, and describe the 
unisexual flowers of some of the folowing dicecious plants and one of 
the moncecious plants : 
ieee meadow rue. 
Dicecious plants. & . -e Ge ww willow. 
i poplar. 
walnut, oak, chestnut. 
Moncecious plants . . . . . . . . 4 hickory, alder, beech. 
birch, hazel, begonia. 
178. Symmetry of the Flower. — Most angiosperms have 
symmetrical flowers. The simplest are those whose parts 
are arranged as in Figs. 97, 118, having radial symmetry. 
Any 
SN 
Fic. 101. Bilaterally Symmetrical k 
Corolla of Sweet Pea. | 
1, side view; B, front view dissected ; 
8, standard; w, w, wings; k, keel. 
A higher type of flower is that which shows bilateral sym- 
metry, as in Figs. 101, 128. If the drawing of such a 
flower were folded along the central line, one half of the 
drawing would cover and correspond with the other half. 
Some flowers are wholly irregular, showing no sort of 
symmetry. 
179. The Receptacle. — The parts of the flower are borne 
on an expansion of the flower-stalk known as the receptacle. 
