174 Miscellaneous Objections to the Chap. vn. 



portance. Prof. Braun mentions a Fumariaceous genus, in which 

 the flowers in the lower part of the spike bear oval, ribbed, one- 

 seeded nutlets ; and in the upper part of the spike, lanceolate, two- 

 valved, and two-seeded siliques. In these several cases, with the 

 exception of that of the well developed ray-florets, which are of service 

 in making the flowers conspicuous to insects, natural selection can- 

 not, as far as we can judge, have come into play, or only in a quite 

 subordinate manner. All these modifications follow from the relative 

 position and inter-action of the parts ; and it can hardly be doubted 

 that if all the flowers and leaves on the same plant had been sub- 

 jected to the same external and internal condition, as are the flowers 

 and leaves in certain positions, all would have been modified in the 

 same manner. 



In numerous other cases we find modifications of structure, which 

 ;are considered by botanists to be generally of a highly import- 

 ant nature, affecting only some of the flowers on the same plant, 

 .or occurring on distinct plants, which grow close together under the 

 same conditions. As these variations seem of no special use 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 indifferently tetra- 

 merous, 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 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 aestivation is 

 almost as frequently that of the Rhinanthidege as of the Antirrhi- 

 nideas, to which latter tribe the genus belongs. Aug. St. Hilaire 

 gives the following cases : the genus Zanthoxylon belongs to a 

 division of the Rntacea3 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 3-locular; and in 

 H. mutabile, "Une lame, plus ou rnoins large, s'etend 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 towards the southern ex- 

 treme of the range of Gomphia oleseformis two forms which he did 



