POSITIVE DEDOUBLEMENT. 73 



formed externally instead of, as in Datura, internally 

 to the normal whorl ; their position on the corolla may 

 be merely a question of the mode of development of 

 the single rudiment from vs^hich both have their 

 common origin : if the rudiment divides at an early 

 period into two equal parts, two equal corollas, exhibit- 

 ing normal orientation, will result ; if the innermost 

 portion of the rudiment develops more strongly and 

 ahead of the outer portion, the latter will appear, in 

 the mature state, as an appendage of the former on 

 its outer (dorsal) side, and this would give rise to 

 such structures as we find in " Gloxinia " and in the 

 abnormal corolla of Datura fastuosa ; according to the 

 degree of strength or weakness of the outer portion 

 of the rudiment will be its appearance in the mature 

 condition : a free independent corolla, a well-developed 

 corolla-like enation on the normal one, or in the form 

 of insignificant separate petaloid enations. Moreover, 

 the more the corolla-character of the structure is main- 

 tained the more likely is its orientation to be normal ; 

 the more the enation-character predominates the more 

 likely is the structure, like all enations, to obey the 

 law of laminar inversion and exhibit inversed orienta- 

 tion of its surfaces (the two cases are exemplified 

 respectively by the first extra whorl in Datura and 

 the " catacoroUa " of " Gloxinia''). 



The appearance of the enation-structure in certain 

 forms of " Gloxinia " in the guise of separate petals, 

 we can quite well understand, for it is well known 

 that in many double flowers of the Gamopetal*, as, 

 for example, in the oleander, the corollas are poly- 

 petalous.. 



A similar phenomenon to that of Datura and 

 " Gloxinia " is found occasionally in Primula sinensis, 

 but here the enations are on the inner side of the 

 corolla ; which abnormality Masters classes amongst 

 the double flowers. To quote his description : " In 

 these flowers the calyx is normal, . . . the limb 

 [of the corolla] is divided into ten fimbriated lobes. 



