366 ORGANOGRAPHY. 



calyx is occupied by two bracts, and there is only one stamen 

 present , this of itself constitutes the flower, which is thus re- 

 duced to its simplest condition. 



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 Scrophnlaria 

 the fifth stamen is reduced to a scale; in the Umbelliferai the 

 limb of the calyx is commonly abortiA'e, while in the Com- 

 posite {,figs. 953 and 955) it is reduced to a pappose form. 

 Many of the so-called nectaries of flowers are merely trans- 

 formed stamens. In unisexual flowers, such as Tamus, the 

 stamens are frequently present as little scales. In cultivated 

 semi-double 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 tlie parts of the androecium and gynoecium are thus 

 converted into petals. 



4. Irregularity. — This irrejiularity may be produced by 

 three different causes, — namely, unequal growth of the memljers 

 of a whorl; unequal degree of union; and abnormal development 

 of the thalamus or axis of the flowei*. The two first causes 

 cannot well be separated, and will V)e treated of under one head. 



a. Unequal yroivt/i, and unequal degree of union of the members 

 of a whorl render such whorls irregular, and ])roduce what arc 

 called irregular flowers. These irregular forms have been 

 already treated of in describing the different floral organs. All 

 the examples of irregular forms of calyx and corolla therefore, 

 which have been alluded to under their rcs])ectivc heads, will 

 afford good illustrations. The stamens of Papilionacejc will 

 afford an example of unequal union in the staminal wliorl. 



b. Abnormal development of the thalamus or axis ofthejloxoer. — 

 The irregular forms of flowers due to this cause have been also 

 alluded to when describing tlie thalamus. Thus the flowers of 

 the Ncluml)inm (^f\g. 640), Ranunculus {jig. 530), Kosc {jig. 

 439), Dianthus {j^g. 587), Geranium {fig 626), &c., will furnish 

 examples of this form of irregularity. 



