ORGANS OF REPRODUCTION. 359 



successive whorls alternate with each other, as shown in figures 

 763 and 765; thus here, the sepals alternate with the petals, 

 the petals with the stamens, and the stamens with the carpels 

 or parts of the pistil. 



A perfectly normal and typical flower should possess a calyx, 

 corolla, stamens, and carpels, each of which should be so ar- 

 ranged as to form but a single circle of parts; the ditferent 

 whorls should consist of an equal number of members; the parts 

 of successive whorls should alternate with one another; and the 

 organs of each whorl should be uniform in size and shape, and 

 distinct from each other and from the surrounding whorls. 

 This normal and typical flower is, however, liable to various 

 alterations, arising from several disturbing causes, which modify 

 and disguise one or more of the above typical characters. Some 

 of these disturbing causes have been already aUuded to in the 

 description of the diflferent organs of the flower, but it will be 

 necessary for us to investigate them more fully here, and 

 chissify for systematic study. All the more important devia- 

 tions of the flower from its normal character, may be arranged 

 under the following heads: — 



1st. The adhesion or union of the parts of the same whorl; 

 or those of different whorls. 



2nd. The addition of one or more entire whorls in one or 

 more of the floral circles; or increase in the number of parts, 

 Avhich is due to the multiplication by division of any or all of 

 the organs of a whorl. 



3rd. The suppression or abortion of one or more of the 

 floral whorls ; or of some parts of a whorl. 



4th. Irregularity produced by unequal growth ; or unequal 

 union of the members of the same whorl; or to abnormal de- 

 velopment of the thalamus. 



That part of Botany Avhich has for its object the investiga- 

 tion of the various deviations from normal structure, both in 

 the flower and other parts of the plant, is called Teratology. 



We shall describe the above causes of deviation in the order 

 in which they are placed above. 



1. The changes due to union or adhesion of parts. — "We 

 diA"ide these into two divisions: namely, the union of the mem- 

 bers of the same whorl; and the adhesion of the different whoi'ls ; 

 the first is frequently termed coalescence, and the \aiiQV adnation. 



a. Coalescence. — This is of very common occurrence in the 

 members of the different whorls of the flower. Thus it occurs in 

 the calyx, when it becomes monosepalous ; in the corolla, when it 

 is monopetnlous ; in the filaments, when it gives rise to monadel- 

 phous, diadelphous, and polyadelphous stamens ; in the anthers, 

 when they are syngenesious ; and in the pistil, when the carpels 

 are syncarpous. All these modifications have been fully de- 

 scribed under their respective heads. 



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