136 MANUAL OP BOTANY 



the flowers of some RosacesE. There are in two species of 

 OratmgiLS ten stamens arranged in a single whorl; but they are 

 not exactly opposite the sepals and petals, as they should be, on 

 the hypothesis of the addition of a whorl of five to the andrce- 

 eium, but stand in pairs opposite to the sepals. In NutfalUaa, 

 third whorl of five is added, which are opposite to the petals. In 

 other species, additional whorls of five each are present, making 

 as many as fifty stamens in some flowers. 



b. Chorisis or Deduplication. — This is generally looked upon 

 by botanists as another means of multiplication of the parts of 

 a flower. It consists in the division or splitting of a member 

 in the course of its development, so that two or more mem- 

 bers are produced in the place of one. Chorisis differs from 

 augmentation in the fact that it not only increases the number 

 of parts, bat also interferes with their regular alternation ; for 

 augmentation d.' ;s not necessarily interfere with alternation, 

 though it may obscure it when the number of additional parts is 

 excessive, or when the whorls are crowded together. 



Chorisis may take place in two ways, either transversely, 

 when the increased parts are placed one before the other, which 

 is called vertical, pnrallel, or transversB chorisis ; or collaterally, 

 when the increased parts stand side by side, which is termed 

 collateral chorisis. 



Transverse chorisis is supposed to be of frequent occurrence. 

 The petals of Lychnis {fig. 327, a) and many other Caryo- 

 phyllaceous plants exhibit a little scale on their inner surface at 

 the point where the limb of the petal is united to the claw. A 

 somewhat similar scale, although less developed, occurs at the 

 base of the petals of some species of Banmiculus (fig. 324). 

 The formation of these scales is supposed by many to be due-to 

 the chorisis or unlining of an inner portion of the petal from 

 the outer. Each petal oi Parnassia {fig. 326) has at its base a 

 petal-like appendage divided into a number of parts, somewhat 

 resembling sterile stamens ; this also is stated to be produced by 

 transverse chorisis. 



In plants of the orders Rhamnaoese {fig. 251), and others, the 

 stamens are placed opposite to the petals, hence they have been 

 supposed by many botanists to be produced by chorisis from the 

 corolla ; but others explain this opposition of parts by supposing 

 the suppression of an intermediate whorl. Transverse chorisis 

 is frequently to be found in the androeoium, but it is less frequent 

 in the gyncEcium. An example of transverse chorisis in the 

 gynoecium is furnished, however, by Crassula {fig. 245), where 



