POSITIVE DfoOUBLBMBNT. 103 



General CoNcmsroNS. — More will be stated under 

 tills heading in a later section, when reduction-phe- 

 nomena are considered. In the meanwhile it may be 

 said that the phenomena of positive dddoublement are 

 in a general way reversional in character. Some of 

 them, however, may be regarded as exhibiting rever- 

 sion in one aspect, but not in another. For instance, 

 in the lily afflicted with " petalomania " the elongation 

 of the axis may be regarded as a reversion, as also the 

 formation of great numbers of spirally-arranged foliar 

 organs ; but the petaloid character of the latter cannot 

 be so regarded. Many of the cases of dMoublement 

 may perhaps be considered as early stages in fasciation 

 of the flower. Whether a reversionary meaning is to 

 be attached to the formation of extra corolla- whorls in 

 Datura and Sinning ia it is difficult to say. If so, it 

 can only be in the wider, vaguer sense of the term. 



" Positive d^doublement " is merely a (frequently 

 reversionary) increase in the number of whorls or 

 members of whorls. "Fasciation " is an increase in the 

 number of whorl members representing early stages in 

 the splitting of tlie flower into two or more. 



BIBLIOGRAPHY. 



Abbado. — "Mostrnosita in fiori di Pseonia Moutan Sims." 



Bull. Soc. bot.Ital.,no.6 (1896), pp. 125-128 [pleiotaxy]. 

 Benecke. — " Zur Kenntniss des Dicagramms der Papaveracete 



und Rhoeadinea;." Engler's Bot. Jahrb., Bd. ii (1882), 



pp. 373-390, pi. iii. 

 BoWEE. — Studies in the MorpTiology of Spore-producing 



Members : II. Opliioglossacese. London, 1896. 

 " Note on Abnormal Plurality of Sporangia in 



Lycopodinm rigidum Gmel." Ann. Bot., vol. xvii (1903), 



pp. 278-280. 



"Notes on the Morphology of Oinliioglossum [Qheiro- 



glossa) palmatum L." Ann. Bot., vol. xxv (1911), pp. 

 277-298, pis. xxii-xxiv. 

 Beown, N. B. — "A remarkable flower of Stapelia revoluta." 

 Gard. Ghron., ser. 3, vol. xxxvi (1904), p. 206. 



