294 METAMORPHY. 



anther-lobes are usually atrophied, and little or no 

 pollen is formed. 



An occurrence of this nature in Tacsonla pinnati- 

 siipala, in conjunction with the partial detachment of 

 the stamens from the gynophore, led Karsten to estab- 

 lish a genus which he called Pogrjendorffia} 



From the subjoined list of genera in which petalody 

 of the stamens, in some form or other, has been 

 observed, it will be seen that it happens more often 

 in plants with numerous distinct organs (Polypetalae, 

 Polyandria, Polygynia, &c.) than in other plants 

 with a smaller number of parts, and which are more 

 or less adherent one to the other. The tendency to 

 petalification is, moreover, greater among those plants 

 which have their floral elements arranged in spiral series, 

 than among those where the verticillate arrangement 

 exists ; and in any given flower, if the stamens are 

 spirally arranged while the carpels are grouped in whorls, 

 the former will be more liable to petalody than the 

 latter, and vice versa. It has been before remarked, 

 that this condition is far more common in plants whose 

 petals, &c., have straight veins, like those in the 

 sheath of a leaf, than in those the venation of which 

 is reticulate, as in the blade of the leaf. It must also 

 be remembered that in the same genus, even in the 

 same species, different kinds of doubling occur. 

 Familiar illustrations of this are afforded in the case 

 of anemones, columbines, fuchsias, and other plants. 



The existence of " compound stamens " in some 

 flowers, as pointed out by Payer, and others, and the 

 researches of Dr. Alexander Dickson, confer additional 

 importance on the subject of petalody, and necessitate 

 the examination of double flowers ynih. special reference 

 to these compound stamens, and to the order of their 

 development. The presence of these compound sta- 



' Karsten, ' Flor. Columb. Spec.,' tab. xxix. 



' See Dickson, " On Diplostemonous Flowers," ' Trans. Bot. Soc. 

 Edin.,' vol. viii, p. ICM) ; and on the Andi-oeciiim of Mentzelia, Ac, in 

 Secmann's * Journal of Botany,' vol. iii, p. 209, and vol. iv (1866), p. 273 

 {PotentUla, &c.). 



