208 PBINOIPLES OF PLANT-TERATOLOGT. 



hence this extra stamen may be regarded as probably 

 representing a third carpel which has become trans- 

 formed. Zimmermann describes interesting cases of 

 the gradual transformation of carpels into stamens in 

 the crack-willow {S.fragilis) (fig. 137). 



Plate XLTX, fig. 9, shows a carpel of Begonia 

 bearing an anther. 



Wigand's observations illustrate the fact that 

 metamorphosis is very frequently accompanied by 

 positive d^doublement (an instance has just been 

 cited in Linaria), for when the equilibrium of the 

 flower becomes upset, reversion in more than a 

 single respect is likely to occur. In the maize male 

 spikelets sometimes occur in the female inflorescences 



Fig. 137. — Salix fragilis (Crack-Willow). Carpels changed into 

 stamens. (After Zimmermann.) 



or " cobs." They usually appear in the terminal 

 portion of the cob, either as a continuation of the 

 normal rows of spikelets, or on a special prolongation 

 of the axis, as in Typha. But they occur more fre- 

 quently, as might be expected, when the cob becomes 

 resolved into its original separate spikes, and in that 

 case, again, at the ends of the branches ; such an 

 androgynous inflorescence comes to resemble the 

 terminal male panicle of the plant. More rarely do 

 the male spikelets occur in the middle region of the 

 cob, mixed up with the female spikelets. 



Blaringhem obtained, by artificial mutilation, cobs 

 in which all the female spikelets were replaced by 

 male ones, yet the glumes and palese remained the 

 same as in the female flower. 



Very interesting are those cases in which the 

 nucellus (megasporangium) of the ovule produces 



