208 EXTRACTS FROM FOREIGN PERIODICALS. 



inverse ratio of the mean temperature under the influence of which the vegetation 

 takes place, so that the produce of this number of days by the temperature is 

 constant. This result, says M. Boussingault, is not only important as indicating 

 that the same annual receives throughout, in the course of its existence, an equal 

 portion of heat ; it further points out the possibility of naturalizing a plant in any 

 country, provided the mean temperature of the month is known. 



All the results of M. Boussingault's researches are condensed in a table 

 published in our foreign cotemporary the Bibliotheque de Geneve, to the fourteenth 

 No. of which (for Feb., 1837) we beg to refer our readers. 



3. Saccharine Nature of Beet-root. — The second]supplement to the General 

 Catalogue of the Royal Botanico- Agricultural Society, published by Messrs. Bur- 

 den, Sen., & Co. (Turin, 8 vo., 1837), written in Italian, contains instructions for 

 the cultivation of Beet-root, and of plants used as food in general. The author 

 considers the Beet-root first as a nutritive root and then as a sacchariferous plant. 

 We observe, in a note, that M. Falcoz, of Chambery, obtained 60,000 kilogr. 

 of roots per hectare, that M. Bonafous estimates the average produce at 20,000 

 kil., and that it may be regarded as between these two numbers. 



4. Expansion and Sleep of Leaves. — The movements, observes M. Dutrochet, 

 by which leaves take the alternate positions of waking and sleeping, have their 

 seat exclusively in the peculiar curves situated at the base of their petioles, 

 and which constitute to them alone the short petiole of their leaflets. These 

 curves are sufficiently large in the Kidney-bean (Phaseolus vulgaris) to render 

 the study of their internal structure easy. The leaves of this plant display the 

 phenomena of expansion and of sleep in a very remarkable manner ; their leaflets 

 lower their points at night, and their limbs regain the horizontal posture during 

 the day. 



The curvature which constitutes the entire petiole of a leaflet of the Kidney- 

 bean, displays, under the epidermis, a thick layer of cells arranged in longitudinal 

 series, and which generally decrease in size from within outwards, so that when 

 the turgescence of the tissue which they form by their junction takes place, this 

 cellular tissue would curve by directing the concavity of the curvature outwards. 

 This is also proved by experience ; for by plunging into water a thin blade" raised 

 longitudinally upon this cellular tissue, it curves powerfully in the direction above 

 indicated. If the blade, thus curved, be removed into syrup, it curves in the. 

 opposite direction. Thus this cellular tissue is incurvable (i. e., is capable of 

 curving inwards) by endosmose ; it represents, by its disposition, a hollow cylinder 

 of which all the longitudinal portions, if separated from each-other, would tend 

 towards a natural position, by curving outwards. The cells of the two or three 

 innermost layers of this cellular tissue only contain air ; under these pneumatic 

 cells is found a layer of fibrous tissue, -composed of transparent fibres, of great 



