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 Bihliotheque 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 Rogal Botanico-Agricultural Society , published by Messrs. Bur¬ 
den, Sen., & Co. (Turin, 8vo., 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 ( Pkaseolus 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 
