298 THE ORIGIN OF SPECIES 



the flowers on the same plant, or occurring on distinct 

 ph\nts, which grow close together under the same condi- 

 tions. As these variations seem of no special use to the 

 plants, they cannot have been influenced by natural selec- 

 tion. 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, flower? indifferently tetramerous, pentamerous, 

 etc., 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 offer 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 SBStivation is 

 almost as frequently that of the Rhinanthidese as of the 

 Antirrhinideae, to which latter tribe the genus belongs. 

 Aug. St.-Hilaire gives the following cases: the genus 

 Zanthoxylon belongs to a division of the Rutaceae 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 described as unilocular or 8-locular; and in H. 

 mutabile, "TJne lame, plus ou moins large, s'^tend entre 

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

 officinalis, Dr. Masters has observed instances of both 

 marginal and free central placentation. Lastly, St.- 

 Hilaire found toward the southern extreme of the range 

 of Gomphia oleaeformis two forms which he did not at 



