Academy of Sciences In Paris* 345 



mosses, and some genera of the family of ferns. Each family is pre- 

 ceded by general considerations on the characteristics of the existing 

 plants which it contains, on their anatomical organization, their ge- 

 neric divisions, and their distribution on the surface of the earth. The 

 fossil plants of the same order are then compared with these, and the 

 geological circumstances under which they are found minutely and 

 accurately described. The anatomical structures of the families of 

 the equiseta and ferns, particularly the organization of the petioli, 

 and the characteristics of the stems of the latter, are, for the first 

 time, fully and accurately described, and all the plates and tables of 

 the localities in which the different fossils are found are remark- 

 able for their scrupulous fidelity. In conclusion, the reporter ob- 

 served that the philosophical spirit in which the researches of M. 

 Brogniart had been carried on, and the importance of the facts 

 which he had collected, as well in a geological as in a botanical point 

 of view, specially merited the highest and most signal approbation of 

 the Academy. 



Structure of the Stems of Plants. At the meeting of the 25th of 

 July, MM. Desfontaines and Cassini made a report to the Academy 

 on a memoir by M. Adolphe Brogniart, entitled * Observations sur 

 la structure et la mode d'accroissement des tiges dans quelques 

 families de plantes dicotyledones.' The object of this memoir is to 

 supply the deficiency in science observed by M. de Candolle, who 

 has remarked that the classification of plants can never be considered 

 as truly according to nature, until the characteristics derived from 

 the organs of vegetables can be made constantly concurrent with 

 those derived from the organs of reproduction. M. Brogniart endea- 

 vours to attain this end by proving that several families of plants 

 have distinctive and peculiar characteristics, observable in the struc- 

 ture of their stems. After alluding to the general difference arising 

 from the fact of the plants being monocotyledons, or dicotyledons, the 

 author remarks that, in the greater part of the ligneous dicotyledons, 

 the fibrous fascicules, disposed in concentric circles, which form the 

 successive beds %>f wood and liber, approach each other laterally, 

 and are united at various distances ; so that the radii, or rather 

 the medullary plates which separate them, have their length fre- 

 quently interrupted by reticulations. This disposition, although 

 general, is not universal : thus, in the vine and the cimis, the me- 

 dullary radii form very long continuous plates without interrup- 

 tion. M. Brogniart has made the same observation in all the 

 menispermoe which he has been able to notice, as well as in the 

 ligneous ranunculi, such as the clematis, in the aristolochia, and in the 

 pipera. It might be hence concluded, that the structure belonged 

 generally to creeping or climbing plants ; but the author, not hav- 

 ing found it in the Bignojiia, periploia, honeysuckle, ivy, &c. ; and 

 having observed it in the berberes, is induced to suppose it a charac- 

 teristic, independent of the manner of growing, and having relation 



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