150 EXTRACTS FROM FOREIGN PERIODICALS. 



substance which, in Algce, surrounds the cells, is found in higher plants, though 

 in a smaller quantity ; he names it " intercellular substance" ; 2nd., that this 

 substance is always homogeneous, and is never seen in the fibrous form. 



Illustrations of various organs, as seen under powerful magnifiers, accompany 

 this work. They explain the point under consideration with great clearness. 

 Let us follow the author in the account of the observations which led him to the 

 above conclusions. He there notices the tissue in different plants, passing from 

 the lowest classes of the kingdom up to the most complicated. 



In Nostochinece the intercellular substance forms nearly the whole plant. It 

 exists in a semi-liquid indeterminate form, and serves as a matrix to the cells 

 which it connects. In the Oscittatorice the cells are already united at each end, 

 like beads on a string. Each of these cellular filaments is covered with a case 

 of more compact cellular substance. The cellular thread may easily be removed, 

 when the homogeneous structure of the casement, in a single piece, is distinctly 

 seen. A certain number of chaplets and their envelops are reunited by other 

 more fluid intercellular matter, and form an aggregate of different structures. 



In Scgtomena and Confervce, the organization is similar, except that the 

 cellular threads and their envelops are no longer united, but form distinct parts. 



Passing from those species of Algce where the cells are arranged in a single 

 row, end to end, to those of a more complicated structure, where the cells are in 

 many rows, the same substance still occurs, not only on the exterior of the 

 plant, but also in the interstices of the cellules. If these cellules are few and 

 distant from each other, the intercellular substance is very abundant, and forms 

 the greater portion of the tissue. If, on the contrary, the cells are united, it is 

 collected at the corners, and is only found in very thin layers between the coats 

 of the cells. These two cases are observed in marine Algce. Intercellular pas- 

 sages have never been discovered here, on account of the substance which fills all 

 the voids. 



It is found in Lichens, but less abundantly. It must be looked for between 

 the rounded cells which form the external layer of the thallus. 



In higher plants, with distinct leaves, the intercellular substance is less easily 

 seen, on account of the existence of passages, and because of the greater pressure 

 of the cells. There is, however, perhaps no plant in which it is not found in one 

 organ or another. 



In Mosses and JungermannicB it is distinctly seen towards the extremity of 

 the leaves, in the intervals of the cells. 



In Fems it is very evident between the elongated cellular tissue surrounding 

 the vessels. The rhizoma of Pteris aquilina (the Common Brake), and the stems 

 of arborescent Ferns, furnish excellent examples ; but care must be taken not 

 to confound with intercellular substance the external layer of cells, which is 



