254 Scientific Intelligence. 



of plants were investigated with the result that the tissues are 

 differentiated either from two or from three initial layers which 

 arise independently, each by the repeated divisions of one of its 

 cells. Among the monocotyledons there are usually two such 

 initial layers, while in dicotyledons the occurrence of three is 

 more common. b. l. r. 



2. Typical Elms and other trees of Massachusetts. Introduc- 

 tion by Oliver Wendell Holmes, descriptive text by Lorin 

 L. Dame, and illustrations by Henry Brooks ; folio of 90 pp. 

 with 58 plates; Boston, 1890. — While not in the narrower sense 

 a scientific work this book is eminently deserving of mention here 

 as containing much that is of interest to the botanist. With great 

 care Messrs. Dame and Brooks have searched out, described, and 

 illustrated examples of many different types of elms, maples, 

 oaks, and other trees ; and their work shows, in a striking way, 

 what remarkable diversity of form is manifested by individuals 

 of the same species. The plates, which have been excellently 

 prepared by the photogelatine process, represent, in most in- 

 stances, the entire tree, showing very clearly its characteristic 

 habit, while a rod of given length placed near its base gives an 

 easy means of judging its size. As the title would indicate, pre- 

 eminence is given to the American elm, and over twenty more or 

 less clearly marked types of this magnificent tree are represented. 

 The introductory chapter by Dr. Holmes is a graceful contribu- 

 tion to a work, which was long ago suggested by him, and which 

 has been carried out thoroughly in his spirit. b. l. r. 



3. Weber die JBalken in den Holzelementen der Coniferen ; by 

 Carl Muller (Berichte der deutsch. bot. Gesellsch., viii, pp. 17- 

 46.) — The occasional presence of slender cross-bars or "beams" 

 of cellulose in the tracheids of the Coniferoe was first mentioned 

 by Sanio, and has since been noted by a number of observers, 

 none of whom, however, have, until now, made any extended 

 study of this curious phenomenon. In the present paper Mtiller 

 summarizes the results of a series of observations to be described 

 in detail at some future time. It appears from these studies that 

 such beams are of much more common occurrence than hereto- 

 fore supposed. While considerably more frequent in some species 

 (e. g. Araucaria Brasiliensis and Ginko biloba) than in others, 

 in none of the twenty-eight Coniferce examined were they en- 

 tirely wanting. Occurring alike in stem, root, and branches they 

 are to be found not only in the wood, but in the cambium and 

 bast as welL; and, although generally seen in the tracheids and 

 sieve-tubes, they have occasionally been observed in the paren- 

 chyma of the xylem and cambiform elements of the bast. 



These peculiar structures among the Coniferm recall, of course, 

 the similar cellulose bars occurring elsewhere (e. g. in Caulerpa) 

 as well as the crystal-bearing beams described by Rosanoff. On 

 grounds of their peculiar origin and development, however, 

 Mtiller is inclined to regard them as distinct from other similar 

 structures, and suggests that they be called the beams of Sanio 



