272 MISCELLANEOUS OBJECTIONS TO THE [Chap. VIL 



to the plants, they cannot have been influenced by 

 natural selection. Of their cause we are quite ignorant; 

 we cannot even attribute them, as in the last class of 

 cases, to any proximate agency, such as relative position. 

 I will give only a few instances. It is so common to 

 observe on the same plant, flowers indifEerently tetram- 

 erous, pentamerous, &c., that I need not give examples; 

 but as numerical variations are comparatively rare when 

 the parts are few, I may mention that, according to De 

 Candolle, the flowers of Papaver bracteatum oSer either 

 two sepals with four petals (which is the common type 

 with poppies), or three sepals with six petals. The 

 manner in which the petals are folded in the bud is in 

 most groups a very constant morphological character; 

 but Professor Asa Gray states that with some species 

 of Mimulus, the aestivation is almost as frequently that 

 of the Rhinanthidese as of the Antirrhinidese, to which 

 latter tribe the genus belongs. Aug. St. Hilaire gives 

 the following cases: the genus Zanthoxylon belongs to 

 a division of the Eutacese with a single ovary, but in 

 some species flowers may be found on the same plant, 

 and even in the same panicle, with either one or two 

 ovaries. In Helianthemum the capsule has been de- 

 scribed as unilocular or 3-locular; and in H. mutabile, 

 "Une lame, plus ou mains large,s'eiend entre le pericarpe 

 et le placenta." In the flowers of Saponaria ofiicinalis. 

 Dr. Masters has observed instances of both marginal 

 and free central placentation. Lastly, St. Hilaire found 

 towards the southern extreme of the range of Gomphia 

 oleEeformis two forms which he did not at flrst doubt 

 were distinct species, but he subsequently saw them 

 growing on the same bush; and he then adds, " Voila 

 done dans un meme individu des loges et un style qui 



