362 SYMMETRY .OF THE FLOWER.—IRREGULARITY. 
from Jussieu will show this fact in a remarkable manner (jig. 
801). Thus, in No. 1 we have a flower consisting of but two 
whorls, the petals and carpels being suppressed ; in No. 2, gee 
the same whorls are present, one of the stamens is absent ; 
No. 3 two stamens are abortive ; in No. 4 the calyx is seecntinds; 
and one stamen, the place of the calyx being occupied by three 
bracts ; while in No. 5 the place of the calyx is occupied by 
two bracts, and there is only one stamen present ; this of itself 
constitutes the flower, which is thus reduced to its simplest 
condition. 
Fie. 801. 
Fic. 800. 
z 2 
-_—a. aN 3 4 S 
PD ~ eelen) 
a~ NEY, \e8) Oj 
Fig. 800. Diagram of the flower of 7ropa@olum pentaphyl- 
(¢ Q lum.— Fig. 801. Diagram of flowers of Euphorbia- 
0) ceous plants becoming more and more simple. After 
Jussieu. 
Sos 3) 1. Staminate flower of 77 agia cannabina. 
2. A “ Tragia volubilis. 
3. - - Anthostema senegalense. 
4. = - Adenopeliis colliguaya. 
5. = an Euphorbia. 
Besides the above examples of the suppression of parts, 
there is another kind of suppression, to which the term abortion 
more properly applies. This consists in the degeneration or 
transformation of the parts of a flower. Thus in Scrophularia 
the fifth stamen is reduced to a scale ; in the Umbelliferze the 
limb of the calyx is commonly abortive, while in the Composite 
it is either abortive (fig. 465), membranous (fig. 466), or re- 
duced to a pappose form. Many of the so-called nectaries of 
flowers are merely transformed stamens. In unisexual flowers 
such as Tamus, the stamens are frequently present as little 
scales. In cultivated semi-douwble flowers, such transformations 
are very common ; thus we frequently find the stamens and 
carpels partially transformed into petals ; or when the flowers 
are entirely double, all the parts of the androecium and gyncecium 
are thus converted into petals. 
4. IrrEGULARITY.—This may be produced by three different 
causes—namely, unequal growth of the members of a whorl ; 
unequal degree of union; and abnormal development of the 
thalamus or axis of the flower. The first two causes cannot 
well be separated, and will be, therefore, treated of under one 
head. 
a. Unequal Growth and Unequal Degree of Union of the 
Members of a Whorl.—From these causes such whorls become 
irregular, and we have produced what are called irregular flowers. 
These irregular forms have been already treated of in describing 
the different floral organs. All the examples of irregular forms 
