128 THE STRUCTURE OF FLOWERS. 



CHAPTER Xiy. 



ACQUIRED REGULARITY AND " PELORIA." 



Reversions to Regularity. — Dr. Masters observes that " in 

 cultivated Pelargoniums, the central flower of the umbel or 

 ' truss ' frequently retains its regularity of proportion, so 

 as closely to approximate to the normal condition in the 

 allied genus Geranium; this resemblance is rendered greater 

 by the fact that, under such circumstances, the patches of 

 darker colour characteristic of the ordinary flower are com- 

 pletely wanting, the flower being as uniform in colour as in 

 shape. Even the nectary, which is adherent to the upper 

 surface of the pedicel in the normal flower, disappears, some- 

 times completely, at other times partially. The direction of 

 the stamens and style, and even that of the whole flower, 

 becomes altered from the inclined to the vertical position. 

 In addition to these changes, which are those most commonly 

 met with, the number of the parts of the flower is sometimes 

 augmented, and a tendency to pass from the vertioillate to 

 the spiral arrangement manifested." * 



All the differentiations in an ordinary lateral blossom of 

 Pelargonium brought about by insect agency are, in the above 

 instances, reversed in consequence of the terminal position 

 of the flower. A more complete illustration of the effect of 

 manner of growth and the distribution of nutrition could not 



* Teratology^ p. 221. 



