ii6o A TEXTBOOK OF THEORETICAL BOTANY 



petals as sterilized stamens. Intermediate forms, for example in double 

 and semi-double flowers, indicate that it is the anther connective which 

 contributes the expanse of the new petal and that the filament of the stamen 

 goes to form little but the petal-base. These intermediate petals are often 

 bi-lobed, with a minute apiculus between the lobes, and, where anthers are 

 present on them, the two halves of the anther stand on the outer edges of the 

 two lobes, as may be seen in double flowers of Galanthiis nivalis. This 

 strongly suggests that the petaloid portion of the organ is a broadened 

 anther-connective, rather than a broadened stamen-filament. Traces of 

 this supposedly primitive bi-lobing of the petal may be seen at the apices of 

 the petals in a great many flowers, even where there is no indeterminacy 

 and complete fixity of character prevails, e.g., in many Caryophyllaceae. 



Petals are usually somewhat late in their appearance in the ontogeny 

 of the flower and this has been considered to be connected with their status 

 as arrested stamens. The stamens may be well developed, with their arche- 

 sporium already formed, before the petal-rudiments begin to appear. As 

 Arber points out, in flowers like Clematis where the perianth is of sepal 

 nature, its parts are well in advance of the others in development. It is as if 

 there were a hesitation in the development of the flower at the petal stage, 



associated with their anomalous 

 character, which is neither fully 

 foliar nor fully staminal, but con- 

 tains an admixture and perhaps 

 an opposition of both characters. 

 The almost boundless plasticity 

 of plant form is nowhere shown 

 more prominently than in the vari- 

 ations of the corolla, especially in 

 zygomorphic flowers. To mention 

 particular examples is almost 

 otiose, but the families of Orchid- 

 aceae, Leguminosae and Zingiber- 

 aceae may be cited as among those 

 displaying the greatest diversity of 

 form, colour and texture. The 

 fragile texture of most petals is 

 sometimes modified. In Feijoa 

 selloiviana (Myrtaceae) (Fig. 1131) 

 the petals are fleshy and the entire 

 inner surface, which is bright 

 crimson in colour in contrast to 

 the white outer surface, is nectari- 

 ferous, so that they are eaten in 

 Brazil as sweetmeats. In the annonaceous genus Xylopia the petals are 

 woody and look like the five valves of a dehiscent capsule. Petals are not 

 often hairy, the White Dead Nettle, Latnium album, providing one of the 



Fig. 1 131. — Feijoa selloiviana. Hower show- 

 injj the dark-coloured upper surface of 

 the fleshy petals, which are nectariferous. 



