THE SHAPES OF FLOWERS. 167 



that this primitive radial type had an upright attitude; and 

 that the derivation of a bilateral type from it, occurred along 

 with the assumption of an inclined attitude. 



We come now to a group of cases above referred to, in 

 which radial symmetry continues to co-exist with that con 

 stant lateral attitude ordinarily accompanied by the two- 

 sided form. Two examples will suffice: one a very large 

 flower, the Hollyhock, and the other a very small flower, the 

 Agrimony. Why does the radial form here remain unchanged ? 

 and how does its continuance consist with the alleged general 

 law? 



Until quite recently I have been unable to find any prob 

 able answers to these questions. When the difficulty first 

 presented itself, I could think of no other possible cause for 

 the anomaly, than that the parts of the Hollyhock-flower, 

 unfolding spirally as they do, might have different degrees 

 of spiral twist in different flowers, and might thus not be 

 unfolded in sufficiently-constant positions. But this seemed 

 a questionable interpretation; and one which did not ob 

 viously apply to the case of the Agrimony. It was only on 

 inquiring what are the special causes of modifications in the 

 forms of flowers, that a more feasible explanation suggested 

 itself; and this would probably never have suggested itself, 

 had not Mr. Darwin s investigations into the fertilization of 

 Orchids led me to take into account an unnoticed agency. 



The actions which affect the forms of leaves, affect much 

 less decidedly the forms of flowers ; and the forms of flowers 

 are influenced by actions which do not influence the forms of 

 leaves. Partly through the direct action of incident forces 

 and partly through the indirect action of natural selection, 

 leaves get their parts distributed in ways that most facilitate 

 their assimilative functions, under the circumstances in which 

 they are placed ; and their several types of symmetry are thus 

 explicable. But in flowers, the petals and fructifying organs 

 of which do not contain chlorophyll, the tendency to grow 

 most where the supply of light is greatest, is less decided, if 



