THE FLOWER 263 
ZYGOMORPHIC. _Irregularity may result either from variation in 
form or size of the parts of a whorl, from appendaging, as in the 
calyx of the Larkspur where one of the 5 sepals bears a long spur, 
or from abortion. 
A SYMMETRICAL FLOWER is one in which the parts of each 
whorl are of the same number, or multiples of the same number, 
as the lily or rose. 
Fic. 177.—Diagrams of floral structures. A, Shows the relations of the floral 
parts in a hypogynous flower; B, the same in a perigynous flower; C, the same in 
an epigynous flower; D, a stamen; F, a simple pistil in longitudinal section; F, 
the same in cross-section; G, transitional forms between true petals (left) and true 
stamens (right); H, slight union of two carpels to form a compound pistil; J and 7, 
union of carpels more complete; K and L, cross-sections of compound pistils, of 
three carpels. In B: a, stamen; 6, petal; c, sepal; d, pistil; e, receptacle; f, pedicel. 
In D: a, anther cell; 4, connective; ¢, filament. In £: a, stigma; 4, style; c, ovules; 
d, ovary. (From Hamaker.) 
When either petals or sepals, or both, are present in more 
than the usual number, the flower is said to be “‘double,” as the 
cultivated Rose and Carnation. The doubling of flowers is 
brought about through cultivation and is due either to the trans- 
formation of stamens (as in cases cited), and occasionally of 
carpels into petals, to a division of the petals, or to the formation 
of a new series of petals. 
If one or more pistils are present and stamens wanting, the 
flower is called PistrLLATE, or female; if it possesses one or more 
stamens but no pistil, it is described as SraMINATE, or male; if 
both are absent, NEUTRAL, as marginal flowers of Viburnum 
