Academy of Sciences in Paris. 355 



manner from that which has just been noticed with respect to wheat. 

 In the latter, the organs of fructification appear, but produce no 

 ciFect because they cannot perfectly perform their functions ; in the 

 trees, on the contrary, the organs of fructification do not appear at 

 all. The flower-buds are, in fact, merely metamorphosed leaf-buds ; 

 in order to effect this metamorphosis, it is necessary that the buds 

 should remain a certain time stationary. It is while the bud is in 

 this state of apparent repose, that the formation of the organs of 

 reproduction (which are merely leaves in another form) takes 

 place. In those trees in which the vegetation is too vigorous, 

 the sap is impelled so constantly and so powerfully towards all 

 the buds, that they are never allowed the state of repose necessary 

 to the conversion of the foliaceous organs into floral organs, and 

 consequently are immediately developed into branches laden with 

 leaves. This is the true cause of the absence of flowers in the trees of 

 the tropics, which has been particularly remarked by M. Auguste de 

 St. Hilaire, with respect to the forests in Brasil. This observation 

 explains the means by which horticulturists are enabled to raise fruits 

 out of their natural season, as cherries in January, grapes in April, 

 &c. In order to effect this, it is only necessary to change the period 

 at which the buds remain in that stationary position, which enables 

 them to develope the germs of the floral organs. For this purpose 

 the plants are kept during the winter in a hot-house, where their 

 vegetation is very active ; they are then taken out in the spring and 

 exposed to the north, in a situation sheltered from the solar rays. 

 This change of temperature suspends the vegetation, the plants lose 

 their leaves, the buds become stationary, but being in a temperature 

 favourable to the internal vegetative progress, they form the floral 

 organs, which would never have been called into existence, had they 

 continued in the hot-house. After two or three months of this 

 festival hybernatio?i, the plant is replaced in the hot-house, the vege- 

 tation recommences ; the flower-buds which have been elaborated 

 during its repose become developed, and thus the time of efflores- 

 cence having been artificially changed, fruit is produced, which attains 

 maturity at a season different from that which nature has assigned 

 for its development. 



The memoir was referred to a committee, consisting of Messrs. 

 Mirbel, Cassini, and Auguste de St. Hilaire. 



Night-blowing Flowers. On the 8th of August M. Auguste St. 

 Hilaire read a report on a memo.ir entitled * Flore Nocturne,' by M. 

 Viret. The object of this memoir was to explain the causes of the 

 well-known phenomena of the closing or sleep of plants. M. Viret 

 thus details his theory : 4 My experiments have led me to the fol- 

 lowing conclusions. Cold and wet diminish the transpiration of 

 plants. In that case the sap, instead of ascending towards the top 

 in the branches of the leaves and flowers, as in the daytime, descends 

 towards the roots. Hence the sap-vessels, or the upper parts, which, 



