198 Ubscrvatwii of the Ujicjiii of I 'arictics. 



I refer to a very beautiful instance of the latter (Fig. 36) 

 which I owe to the kindness of Mr. Ernst H. Krelage 

 in Haarlem. 



The origin of double flowers in other groups of flow- 

 ering plants has probably occurred on similar lines with 

 that of double inflorescences. I restrict myself to a con- 

 sideration of doubling by the transformation of stamens 

 into petals, that is, the petalody of the stamens, referring 

 the reader for an account of the other types of doubling 

 to Goebel's well-known monograph.^ 



Occasional petaloid stamens occur fairly commonly 

 both in culture and in nature ; they are so well known 

 that it is not necessary to cite special instances. The 

 curve which represents this variation is unilateral, indi- 

 cating thereby the existence of a latent or semi-latent 

 character.- The attempt to render this active may be 

 made, and if it succeeds'^' the origin of a double variety 

 may be expected. 



Double varieties of this kind tend to vary in the same 

 way as those of composites. If, for instance, the com- 

 mercial Varietates plenae of Clarkia pulchella, Clarkia 

 clccjans. Phlox Dnnnmondi and others are examined, 

 almost all the intermediate stages between nearly hemi- 

 spherical double flowers and flowers wnth normal sta- 

 mens are met with. In such cases it is usually obvious 

 that favoral)le conditions tend to increase ''doubling," 

 a fact which has been known for a lono- time in the 

 case of Anfliciuis nobilis, of some species of N^arcissus, 



* K. GoEr.Ki., Bcitr'dge ziir Kenntniss gcfiilUcr BU'ithcn, in Prings- 

 iieim's Jahrb. f. wiss. Bot., Vol. ly, 1886, p. 207. 



^ Ueher halhe Galton-Curvcn ah Zeichen discontimdrlicher Varia- 

 tion. Ber. d. d. bot. Ges., Vol. XII, 1894, P- i97- 



"Which is, however, by no means always the case. See the ex- 

 periment with Ranunculus bulhosus in §23 of this part. 



