Institute of France, 57 



ordinate effect of the process of vegetation ; and that either by 

 the develop nii^iit of the shoot, or by an interior alteration pre- 

 pared by nature, the petiole is detached when t!ie progress of it* 

 nutrition has brought on the moment when the texture ought to 

 be dissolved which served as it? lien. Thus When a tree, from 

 any given cause, perishes in the season of vegetation, its leaves 

 preserve their adherence. 



We know that several flowers open and shut at certain hours, 

 and that heat and humidity iiiflnence this phaenomenon. M. 

 Desvaux, a botanist of Paris, lias made some observations in this 

 respect on the me^einbnanlhcivinns, plants in which these alter- 

 nate movements are so remarkaide, tliat their generic luime has 

 been taken from the circumstance ; and he has found that the 

 cause resides not in the corolla, as has been supposed, but in tlie 

 cah-x, which by closing forces t!ie corolla to obey its contractions ; 

 so that, if we cut off the calyx, the corolla ren'nains expanded at 

 night as well as by day. 



M. de Mirbel, our colleague, has this year presented us with 

 two series of researches ; the first on the seed, and on the mem- 

 branes which cover it; the second on the pericarp, i.e. the re- 

 ceptacle in which the seed is lodged. He has inquired in the 

 first place, to what extent the analogy established by Malpighi 

 may be regarded as exact, between the tunicas of the foetus in the 

 womb, and those which envelop the seed of plants. The embrvo 

 composed of the plumule and of the radicle being considered "as 

 a foetus, Malpighi thought he recogni'^ed in the testa, or external 

 tunic, the representation of tlie chorion, and in the tegmeii, or 

 interior tunic, that of the amnios : the/jcr/sperwappeared to him 

 to represent the liquor amnii in which the foetus swims. M. de 

 Mirbel finds, on the contrary, tliat originally the seed is only a 

 mucilaginous and continuous cellular tissue, one part of which at 

 first becomes the embryo, and the rest afterwards forms the peri- 

 t\y^Tn\ and seminal tunics, without our being able to say that the 

 embryo at any period floats in a liquid. Tiie mucilaginous state 

 of this tissue, and its transparency, may therefore have suggested 

 the inaccurate comparison made by Malpighi. 



M, de Mirbel, passing to the examination of the pericarp, suc- 

 ceeded in referring the forms of it to a general law, which, deter- 

 mining what is essential in this part of the vegetable, reduces 

 almost to nothing the anomalies which it seems to present in 

 certain families. The general type of every pericarpian capsule 

 appeared to him to be represented by a small box flattened on 

 the sides, and composed of two valves the union of which forms 

 two rims or two sutures, one crooked and the other straight, and 

 by which tiie vessels pass which go to these seeds, eitiier from 

 the body of the plant, from the style, or from the organ which 



transmits 



