ARRANGEMENT OF THE PARTS OF THE FLOW KB. 459 



though he does not appear to have perceived on what the peculiar 

 appearance which mimicked chorisis really depends. 



The arrangement just alluded to, of decussating whorls, is, as is 

 well known, a very common one. It is well seen in the case of 

 the stamens of Aquilegia, which, as shown in the diagram given 

 m the text-books, has the stamens arranged in ten ranks, those 

 of one rank alternating with the next, and so on. In some Ber- 

 beridaceae (as in Epimedium), Guttiferae*, Menispermaceae (e. g. 

 Sychnosepalum), some Lauraceae, etc. the apparent superposition 

 of parts may be explained on similar principles. 



An appearance of superposition is also sometimes brought about 

 by the circumstance that portions of the same phyllome are placed 

 one above the other, as in the case of the divided stamens of 

 Mallows. If a young flower of Malope be examined, the anthers 

 may be observed as if arranged in ten vertical rows, there being in 

 reality five branched stamens, each stamen with two marginal rows 

 of anthers. 



III. True Superposition. 



This occurs in many different manners, and depends on various 



causes. Certain actual, or at least possible, modes of arrangement 



may here be cited, with illustrations. Other examples, together with 



the discussion of the causes producing them, will be given in the 

 sequel. 



1. Sepals superposed to sepals, as in flowers where there is a pleio- 

 taxic calyx (Veg. Teratol. p. 371), as represented by the formula 



S 

 S 



s. 



2. Petals superposed to sepals, thus 



S 

 P. 



Planehon says such superposition may be considered a general 

 rule in Cistaceae (Bull. Soc. Bot. France, ix. 507). 



8. Petals superposed to petals, as in pleiotaxic corollas 



S 



P 

 P. 



* See Aug. de St.-Hilaire, Morphol. Veget. 612 ; Planehon et Triana, Ann. 

 8* Sat. ser. 4, xvi. p. 276. 



