EXTRACTS FROM FOREIGN PERIODICALS. 41 



the Horse, considered with respect to their natural history and nutritive proper- 

 ties. The author passes in review the various families of plants admitted by 

 Jussieu. He indicates the species which grow in France, in the meadows, and 

 their value as food. In the second part he speaks of the different operations 

 which the plants used as food undergo before being given to the animal. Lastly, 

 he enumerates the articles proper to be given to Horses, but which do not form 

 their customary food, as the leaves of trees, roots, tubercles, &c. — Bib. de Ge- 

 neve, Seconde Annee, p. 208. 



3. Sleep of Flowers, by M. Dutrochet. — Some flowers wake but once, 

 namely, on their expansion, and have but one sleep, which immediately precedes 

 the death of the corolla ; such are the flowers of Mirabilis and Convolvulus. 

 Other flowers present, during many days, the waking and sleeping states alter- 

 nately, as, for example, the flower of the Dandelion (Leontodon taraxacum). 

 These are the flowers which I have chosen for my observations. 



The flowers of Mirabilis jalappa and Mirabilis longiflora open their infun- 

 dibuliform corolla? in the evening, and close them on the morning of the 

 following day. This flower may be considered to be formed by the junction 

 of five petals which each possess their median line. The five nerves which 

 sustain the membranous tissue of the corolla, as the whalebone of an umbrella 

 supports the silk, are the sole agents of the motions which effect the expansion 

 of the corolla, and its closing or sleep. In the former case the five nerves curve 

 so as to direct their concavity outwards ; in the second case they bend in such 

 a manner as to direct their concavity towards the interior of the flower, and 

 they thus carry with them the membranous tissue of the corolla to the orifice 

 of its tubular canal. 



Thus the same nerves successively execute at two different times two opposite 

 kinds of curvature. I have examined the internal structure of these nerves in 

 the microscope ; they possess externally acellular tissue the cells of which, dis- 

 posed in longitudinal series, principally decrease in size of the interior towards 

 the external surface, so that at the time of the turgescence of these cellules the 

 tissue which forms them curves in such a manner as to direct its concavity 

 outwards. It is that, therefore, which effects the expansion of the corolla, or 

 its awaking. On the interior surface of each nerve exists a fibrous tissue 

 composed of transparent fibres, extremely fine, and intermixed with globules 

 arranged in longitudinal series. This fibrous tissue is situated between a surface 

 of tubes on one hand, and a surface of superficial cells filled with air on the 

 other ; so that it is placed between two kinds of pneumatic organs. 



I separated by a longitudinal section the cellular and the fibrous tissue which 

 compose the nerve, which I immediately plunged in water. The cellular tissue 

 is curved towards the outside, the fibrous tissue towards the interior, of the 



VOL. III. — NO. XVI R 



