POSITIVE D1SDOUBLEMENT. 



75 



'ins of dedoublement combined : the formation of 

 an extra wliorl of petals (imperfect, of course), and 

 double the number of whorl-members caused by lateral 

 fission (giving rise to polyphylly). 



There is another possibility of explanation, and that 

 is that the petaloid enations in Primula and similar 

 instances are of the nature of the petaloid median loculi 

 of the original anther from which the petal-blade 

 sprang, which have become disjoined from the parent 

 petal and appear as a basal ventral excrescence, or they 

 may represent the basal upturned lobes of the anther, 

 homologous with the corona of Narcissus.* Where 

 this excrescence is comparatively little developed, its 

 orientation is, of course, the reverse of that of the 

 petal ; but in some cases it develops to the size of the 

 parent petal itself, becoming individualized as a distinct, 

 independent petal, so that the necessity for obeying the 

 law of laminar inversion becomes abolished. If this 

 is so, then this phenomenon in the petal is probably 

 precisely the same as that described above in the 

 foliage-leaf ; in both cases all stages exist between 

 small superficial enations and fully-developed, com- 

 pletely individualized foliar organs ; and both would 

 be homologous with the structure resulting from the 

 ventral facial cohesion of two united basal lateral lobes 

 with the midrib of the main leaf ; thus the petaloid 

 enations are also the homologues of the median laminse 

 in virescent, and of the median loculi in fertile anthers. 



This view of the origin of the extra petals in 

 Primula seems the more likely to be true inasmuch as 

 there is a tendency for the petaloid stamens, as de- 

 scribed by Masters in P. vulgaris, to develop enations 

 which in some cases take the form of a median ovuli- 

 ferous placenta probably corresponding to the median 

 loculi of an anther. Masters also figures interesting 

 transitional forms between small median enations, 

 reminding one strongly of remnants of anther-lamellae, 



* This can only be properly understood by reference to a later section 

 where this subject is treated of. 



