Academy of Sciences in Paris. 339 



under the influence of light. Leaves, on the contrary, exhale oxy- 

 gen when exposed to the solar light, and only respire in the shade 

 or during the night. The oxygen which issues from the stomata 

 when the leaf is subjected to the influence of light is only a part of 

 what is produced ; the rest passes from the aerial cavities into the 

 conduits of the petiole, and thence into the whole vegetable tissue. 

 As there is a continual production in the green matter exposed to 

 the light, the oxygen as it is formed impels forward that which has 

 been previously formed; and this mode of circulation supplies in 

 vegetables the place of that which is produced in animals by mus- 

 cular contraction. 



M. Dutrochet concludes by proving, from a variety of experiments, 

 that as the respiration of plants is supported both by the oxygen 

 which is contained in the air penetrating from the exterior, and by 

 that which is formed internally by a chemical action of the light, 

 (which latter is indispensably necessary to their existence,) the ab- 

 sence of light, by diminishing the irritability of the members of the 

 vegetable kingdom, becomes for them a direct cause of asphyxia, and 

 that plants may, therefore, be hindered of respiration, and conse- 

 quently killed either by the action of the air-pump or by total ob- 

 scurity. 



Irregularity of Flowers. On the same day, M. Cassini, in the 

 name of himself and M. Mirbel, made a report on a memoir by 

 M. Adolphe Brogniart, on the relative insertion of the different parts 

 of each floral verticillus, and on its influence on the regularity or 

 irregularity of flowers. According to a modern theory, almost uni- 

 versally adopted, a flower is composed of several verticilli of foliaceous 

 organs superposed and immediately approaching each other, so that 

 the outward or lower verticillus forms the calyx, the next one the 

 corolla, and so on for the stamina and pistils. M. Brogniart, in ex- 

 amining this theory, was led to inquire whether each of these succes- 

 sive rings is in reality a perfect verticillus, that is to say, whether all 

 the pieces which compose it are exactly of the same height round their 

 axis. He remarked, that the calyx of the hclianthemis , of several 

 caryophylii, &c., have evidently some folioli of the calyx situated 

 more externally, and consequently lower than the others. The 

 manner in which the petals cover each other in many flowers 

 during preflorescence, that is to say, before they are fully opened, 

 also appears to him a proof that these pieces are inserted at dif- 

 ferent heights. Thus, according to M. Brogniart's opinion, the 

 similar organs which form each of the rings in most flowers do not 

 form exact verticilli, but are disposed at different heights round the 

 axis, or short branch, which bears them ; and as the lower pieces 

 are necessarily the outermost, it follows, that their mode of envelop- 

 ment must indicate their primitive insertion. Thus the imbricated 

 preflorescence, which presents the pieces of the corolla lapped over 

 each other, indicates their disposition in alternate order, while the 



