306 MISCELLANEOUS OBJECTIONS TO TEE 



fessor Braun mentions a Pumariaceous genus, in which the 

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

 one-seeded nutlets; and in the upper joart of the spike, 

 lanceolate, tvvo-valved and two-seeded siliques. In these 

 several cases, with the exception of that of the well-devel- 

 oped ray-florets, which are of service in making the flowers 

 conspicuous to insects, natural selection cannot, as far as 

 we can Judge, have come into play, or only in a quite sub- 

 ordinate 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 subjected 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 struct- 

 ure, which are considered by botanists to be generally of a 

 highly important 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 indifier- 

 ently 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, accord- 

 ing to _De Candolle, the flowers of Papaver braoteatum 

 offer either two sepals with four petals (which is the 

 common type with poppies), or three sepals with six 

 petals. _ The manner in which tlie petals are folded in the 

 bud is in most groups a very constant morphological char- 

 acter; but Professor Asa Gray states that with some species 

 of Mimulus, the ajstivation is almost as frequently that of 

 the Ehinanthidese as of the Antirrhinidese, to which latter 

 tribe the genus belongs. Aug. St. liilaire gives the fol- 

 lowing cases: the genus Zanthoxylon belongs to a division 

 of the Eutaceas 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 



