DEVELOPMENT OF THE FLOWER. 431 



under the air-pump all the air clinging between the rudiments. 

 Brought under the microscope the rudiments are now seen in 

 apical view, or but slightly inclined, but they are still not trans- 

 parent enough to permit detailed view into their interior. We 

 therefore run in a little potash, and can now, in the most favour- 

 able cases, see at one and the same time the most important stages 

 of development. 



The flower rudiment arises as a bare conical protuberance 

 upon the axis of the inflorescence, close under its apex. No 

 rudiments of bracts are visible, as the Cruciferae generally are 

 distinguished by the absence of bracts from the floral region. 

 When the naked rudiment has attained a not inconsiderable 

 height, begins the formation of the first pair of sepals in the 

 median (antero-posterior) plane, the outer one originating a 

 little earlier, and continuing somewhat more advanced ; the two 

 lateral sepals follow quickly, and quite simultaneously. All these 

 sepals are recognisable in the form of broad protuberances, eaoh 

 occupying about one-fourth of the periphery of the conical flower 

 rudiment. The growing point of the rudiment now bulges out- 

 wards a little, and, alternating with the four sepals, the four 

 petals appear simultaneously, in the form of four protrusions, which 

 give to the growing point a quadrangular form. The sepals now 

 quickly close together with their apices over the rudiment, whereby 

 the outer median (anterior) sepal overlaps the tip of the median 

 inner (posterior). While this is going on, the two protuberances 

 for the lateral (outer) pair of stamens appear ; and then, in the 

 median plane, the two staminal rudiments on either side. Whether 

 these make their appearance as four isolated protuberances, or 

 whether on the other hand they arise each pair from a previously 

 common one, cannot be off-hand determined. This point has 

 given rise to numerous researches, in order to show whether the 

 stamens are isolated from the beginning, or whether we have 

 a splitting, a so-called " dedoublement," whereby two staminal 

 protuberances give rise to four. On theoretical grounds the latter 

 seems the more probable. We should then have the regular 

 alternation of two two-membered whorls of stamens, followed by 

 the two laterally-placed carpels of the pistil, and should thus 

 have resemblances to the nearly allied Fumariaceae. The approxi- 

 mation of the large antero-posterior stamens in pairs likewise 

 supports the dedoublement theory. It is only, however, as a 

 matter of probability that we may conclude that the flower of 



