POSITIVE D^DOUBLEMENT. 59 



DiBTZ. — " Beitrago zur Kenntniss der teratologisclien Falle 



des Mais." Bot. Oentralbl., Jalirg. iii, Bd. x (1882), 



pp. 413-415. 

 DuTAiLLY. — "Anomalies dans I'epi femelle dii Mais." Bull. 



mens. Soc. Linn., Paris, tome ii (1892), pp. 1061-1053. 

 Haeshberger.— "Maize, a Botanical and Economic Study." 



Contrib. Bot. Lab. Pennsylv., vol. i (1892), pp. 75-202; 



pis. xiv-xvii. 

 " A study of the fertile hybrids produced by cross- 

 ing Teosinte and Maize." Loc. cit., vol. ii (1898), pp. 



231-235. 

 Krapft. — Die normale und anorrnale Metamorphose der Mais- 



pflanze. Wien, 1870. 

 Peirson. — "Abnormal Development in Maize." Journ. Bot., 



vol. xlix (1911), p. 34. 

 Penzig. — " Studi morphologici sui cereali. I. Ahomalie 



osservate nella Zea Mays." Boll. Staz. Agr. Modena, 



N. s., Ann. iv (1884). Res. in Bot. Oentralbl., Bd. xxiii 



(1885), pp. 353-354. 



■ Pflanzen-Teratologie, Bd. ii. Genua, 1894. 



ScHUB. — " Beobachtungen in der Floia von Siebenbiirgen." 

 ^ GEster. bot. Zeitschr., Jahrg. ix (1859), pp. 11-12 

 V[Maize]. 

 Watson, S. — "Upon a Wild Species of Zea from Mexico." 



Proc. Amer. Acad. Arts and Sci., vol. xxvi (1891), pp. 



158-161. 



4. POSITIVE DEDOUBLEMENT. 



This is a term borrowed from the writings of Cela- 

 kovsky. When the tendency for an organ to divide 

 becomes all-potent, overriding completely that which 

 makes for unity, the result is the formation of two 

 organs instead of one : this is positive dedouhlement. 

 It has been usually applied to the phenomenon termed 

 by many authors " polyphylly," viz., the increase in 

 number of the members of a floral whorl. But it may 

 equally well be applied to the phenomenon of " pleio- 

 taxy," or the increase in number of the whorls of a 

 flower, and in this dual sense it will here be used. 



The phenomena of positive dedoublement in the 

 abnormal cases considered in the following pages may 



