340 Proceedings of the 



valvary preflorescence, in which no piece laps over another legiti- 

 mately, indicates the disposition inform of verticillus, as perhaps does 

 also the returned preflorescence, in which each piece laps over its 

 neighbour on one side, and is lapped over by that on the other side. 

 Although uniformity is necessary in the arrangement in form ofverti- 

 cilli, it is by no means so in the alternate disposition of the floral pieces 

 any more than in that of leaves ; and M. Brogniart points out several 

 modes of alternation, the most frequent of which is, where the five 

 pieces forming the calyx, or corolla, are disposed on a spiral of rather 

 more than one turn and a half; this is the quincuncial preflorescence, 

 corresponding to the disposition of real leaves in quincunx. M. 

 Brogniart admits that the different modes of preflorescence of the 

 corolla are not always the same in the same plants, and that, there- 

 fore, in order to trace the theory of original insertion from the pre- 

 florescence, it is necessary to regard only the most usual dispositions, 

 and take- no notice of the exceptions, a rule generally necessary in 

 natural history, and which proves the importance of being always on 

 our guard against that spirit of system which will only admit abso- 

 lute theories. 



M. Brogniart, however, endeavours to account for the anomalies 

 of preflorescence by conjectures, more or less plausible, founded 

 principally on the inequality of growth of the different pieces of the 

 corolla, "it is this irregularity which generally constitutes the irre- 

 gularity of the flower, and on this M. Brogniart founds a general 

 law, which is important and worthy of attention, as establishing an 

 interesting relation between the mode of preflorescence and the regu- 

 larity or irregularity of the flower. 



If a family of plants presents a valvary or returned preflorescence, 

 both of which indicate a disposition exactly verticillated, that family 

 will scarcely ever present any irregular flowers, nor will there be 

 found near it any other family derived from the same prototype, and dis- 

 tinguished only by the irregularity of the flowers. If, on the contrary, 

 the preflorescence be imbricated, which indicates an alternate dispo- 

 sition, the same family will often contain regular and irregular 

 flowers ; as, for example, in the Ranunculi, or else close to the 

 family of regular flowers will be found another family having no 

 essential difference, except the irregularity of its flowers. Thus the 

 Leguminosi may be considered as Rosaceae, with irregular flowers, the 

 Fumariye as Papavera with irregular flowers, &c. 



This law, however, is not without exceptions, as the Lobeliae, the 

 Synantherus, the Aristolochiye, have irregular flowers, although 

 their preflorescence is not imbricated, and the floral pieces are conse- 

 quently inserted at the same height. 



M. Brogniart next attributes the irregularity of flowers to the dis- 

 position of the organs of plants to assume a different growth when 

 placed at different heights on their axis, a disposition which is also 

 manifested by leaves, and the existence of which the reporters consider 

 by no means improbable. The author concludes his memoir by 



