ORGANS OF REPKODUCTIOX. 357 



The suppression of whorls and parts of a whorl is well illus- 

 trated by plants of the Euphorbiacese, and the above diagram 

 from Jussieu will show this fact in a remarkable manner {fig. 

 782). Thus, in No. 1 we have a flower consisting of but two 

 whorls, the petals and carpels being suppressed ; in No. 2, while 

 the same whorls are present, one of the stamens is absent ; in 

 No. 3 two stamens are suppressed ; in No. 4 the calyx is sup- 

 pressed, and one stamen, the place of the calyx being occupied 

 by three bracts ; while in No. 5 the place of the calyx is occu- 

 pied by two bracts, and there is only one stamen present ; this 

 of itself constitutes the flower, which is thus reduced to its sim- 

 plest 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 transfor- 

 mation of the parts of a flower. Thus in Scrophularia the fifth 

 stamen is reduced to a scale ; in the Umbelliferse the limb of the 

 calyx is commonly abortive, while in the Compositse it is reduced 

 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-douhle flowers, such transformations are very 

 common ; thus we frequently find the stamens and carpels par- 

 tially transformed into petals ; or when the flowers are entirely 

 double, all the parts of the andrcecium 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 tha- 

 lamus or axis of the flower. The first two causes cannot well be 

 separated, and -will be treated of under one head. 



a. Unequal growth and unequal degree of union of the members 

 of a whorl render such whorls irregular, and produce what are 

 called irregular flowers. These irregular forms have been 

 already treated of in describing the diflferent floral organs. All 

 the examples of irregular forms of calyx and corolla, therefore, 

 which have been alluded to under their respective heads, will 

 afford good illustrations. The stamens of plants belonging to 

 the sub-order Papilionacese of the Leguminosae will afford nu- 

 merous examples of unequal union in the staminal whorl ; and 

 other illustrations will be found under the head of the andrcecium. 



b. Abnormal development of the thalamus or axis of the flower. 

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

 alluded to when describing the thalamus. Thus the flowers of 

 the species of l^elumbium {fig. 640), Ranuncidus {fig. 528), Eosa 

 {fig. 437), Bianthus {fig. 688), and Geranium {fig. 626), will 

 furnish examples of this form of irregularity. 



