182 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



the medullary membrane : 3. The medullary membrane or internal 

 periosteum, is but a continuation of the external periosteum. Oct. 4, 

 1841,^. 681. 



Biot " On the influence of a Lamella-arrangement in the phenomena 

 of Polarisation and Double Refraction, produced by different crystallised 

 bodies." 3\st of May, and 21st of June, 1841, p. 112. 



[We quote the title of this and the following paper by way of refer- 

 ence for those of our readers interested in the laws of Optics.] 



Biot " On the Optical Examination of a substance having the ap- 

 pearance of Natural Manna, and introduced as such in Commerce for 

 Medicinal uses." 10th of Jan, 1842, p. 49. 



Laurent on the Return of the Monstrosities of the Hydra to a Normal 

 State. He has confirmed that the several monstrosities of the Hydra 

 about to produce young, never give birth to other monsters, and that 

 the offspring are normal individuals. He has equally determined the 

 various physiological conditions by means of which they can prolong 

 the monster state, or favour the natural tendency of several of these 

 monsters to return towards their normal form. 2lst of June, 1841, 

 p. 1171. 



Bouchardat on the Theory of Buds, and the Existence of Rhyzogenes. 

 In this memoir the author passed successively in review the various cir- 

 cumstances which may favour or retard the development of roots, when 

 stems are immersed in water ; he exhibited by experiment the influence 

 of light, heat, that of certain acids mixed in different proportions with 

 the liquid ; he examined the conditions of evolution of the roots which 

 depend on the state of the stem and those belonging naturally to the 

 plant, and lastly observed the changes produced in the organs of a 

 branch placed in those circumstances capable of giving rise to buds. 



When a leaf- bearing stem deprived of its root is placed in a vessel 

 filled with \vater, the green parts remain turgid frequently for a very 

 long period, but without evincing any appreciable growth. The water 

 first penetrates at the cut end, but this diffuse and irregular passage does 

 not fail to be interrupted, at least in a great part, by the death of 

 the extremity of the stem. There exists, however, organs which by an 

 isolated kind of development can supply to the defect of absorption re- 

 sulting from this alteration ; these are the lenticels, organs irregularly 

 dispersed on the bark, and having no communication with the interior 

 of the stem. These lenticels, essentially composed of cellular tissue, 

 enlarge on immersion in the fluid, project considerably, and finally be- 

 come organs of absorption, denominated by M. Bouchardat caulinear 

 spongioles ; they are then seen under the form of white tubercular 

 masses, sometimes elongating as true roots, but they may be always 

 distinguished from such in this stage of growth, by never having any 

 direct connection except with the external part of the bark. 



