198 FOUNDATIONS OF BOTANY 
greatly modified leaf (Sect. 222), adapted into a seed- 
bearing organ. Such a pistil may be one-seeded, as in 
Fig. 166, or several-seeded, as in the diagrammatic one 
(Fig. 150) ; itis called a carpel. The calyx and corolla are 
also known as the floral envelopes. Flowers which have 
the essential organs are called perfect flowers. They may, 
therefore, be perfect without being complete. Incomplete 
flowers with only one row of parts in the 
perianth are said to be apetalous (Fig. 139). 
209. Regular and Symmetrical Flowers. 
—A flower is regular if all the parts of 
the same set or circle are alike in size and 
shape, as in the stonecrop (Fig. 140). Such 
: flowers as that of the violet, the monkshood, 
Fig. 139.— Apetal- and the sweet pea (Fig. 141) are irregular. 
ous Flower of F 
(European) Wild Symmetrical flowers are those whose calyx, 
eee corolla, circle of stamens, and set of 
carpels consist each of the same number of parts, or in 
which the number in every case is a multiple of the 
‘smallest number found in any set. The stonecrop is 
y 
Fic. 140.— Flower of Stonecrop. 
I, entire flower (magnified) ; II, vertical section (magnified). 
symmetrical, since it has five sepals, five petals, ten sta- 
mens, and five carpels. Roses, mallows, and mignonette 
