14 THE COLOURS OF FLOWERS. 



The one change is comprehensible and reasonable, 

 the other change is meaningless and absurd. Of 

 course, it is not intended to deny the truth of Wolf's 

 great generalisation in the way in which he meant it 

 — the existence of a homology between the leaf and 

 all the floral organs : but the conception certainly 

 requires to be modified a little by the light of later 

 evolutionary discoveries. The starting-point consists 

 of a plant having three kinds of organs, true foliage 

 leaves, staminal leaves, and carpellary leaves : the 

 petals and sepals are apparently later intermediate 

 modifications, produced in special connection with the 

 acquired habit of insect fertilisation. 



In many other cases besides the waterlily, we know 

 that stamens often turn into petals. Thus the 

 numerous coloured rays of the MesembryantJiemiims 

 or ice-plant family are acknowledged by many 

 botanists to be flattened stamens. In Cmma, w^here 

 one anther-cell is abortive, the filament of the solitary 

 stamen becomes petaloid. In the Ginger order, one 

 outer whorl of stamens resembles the tubular corolla, 

 so that the perianth seems to consist of nine lobes 

 instead of six. In orchids, according to Mr. Darwin, 

 the lip consists of one petal and two petaloid stamens 

 of the outer whorl. In double roses (Fig. 4) and almost 

 all other double flowers the extra petals are produced 

 front the stamens of the interior. In short, stamens 

 generally can be readily converted into petals, especi- 

 ally in rich and fertile soils or under cultivation. The 

 change is extremely common in the families of Ran- 

 iinctdacecB, Papaveraccce^ Magnoliacea^, Malvacece, and 

 RosacecB, all very simple types. Even where stamens 

 always retain their pollen-sacs, they have often broad, 



