ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 985 



therefore excreted especially where starch is being displaced or trans- 

 formed into cellulose, or where metastasis is carried forward uninter- 

 ruptedly. It is formed in large quantities where respiration is active, as 

 in the assimilating organs, germinating seeds, &c. 



(3) Structure of Tissues. 



Importance of the Foliar Fihrovaseular System in Vegetable 

 Anatomy.* — M. O. Lignier states that, in order to find new taxonomic 

 characters or materials for comparative vegetable anatomy, numerous 

 botanists have studied the course of the fihrovaseular bundles. An 

 examination of the facts shows that the fibrovascular system of each leaf 

 is ordinarily independent of that of the neighbouring leaves, and that in 

 each of the bundles that compose the leaf-trace, the differentiation of 

 primary tissues is made from above downwards. The arrangement of the 

 fibrovascular bundles of a stem depends (1) on the symmetry of the stem 

 at the moment of differentiation; -(2) on the form of the foliar system. 

 Finally, it is necessary to compare, first, not the course of the bundles in 

 the stem, but that of the bundles in the foliar fibrovascular system of 

 two branches. The study of the contacts which are established between 

 the diff'erent leaf-traces ought only to take the second place. 



Wall of Suberous Cells.j — M. C. van Wisselingh gives the following 



as a summary of the results of his work : — 



(1) The suberous layer does not contain cellulose. (2) After macera- 

 tion in chromic acid or in potash, or after being heated with solution of 

 potash, the suberous layer is coloured violet by iodine or by chloriodide 

 of zinc. (3) In opposition to the cuticularized layer, the suberous layer 

 does not leave the cellulose base when warmed in glycerin. (4) Different 

 chemical combinations, comprised under the common name of suberin, 

 constitute the essi3ntial element of the suberous layer. (5j Heated in 

 glycerin at the temperature when fats decomj)ose, the suberous layer 

 undergoes decomposition, wbich is not preceded by fusion. (6) The 

 temperature at which this decomposition takes place is different for 

 different plants, and often even for diff'erent parts of the same suberous 

 layer. (7) The ability to resist the action of potash and other energetic 

 reagents is very different for different elements of the suberous layer. 

 (8) After prolonged treatment by these reagents at ordinary temperature, 

 one is able by pressure to divide the suberous layer into small globular 

 bodies or dermatosomes, which consist of suberin, and in consequence 

 differ from those separated by M. Wiesner from many other tissues. (9) In 

 this treatment the suberin which is found between the dermatosomes 

 undergoes a decomposition, a saponification when potash is employed. 

 (10) When potash is employed, it is found that the connections between 

 the dermatosomes are more easily destroyed in a tangential than in a 

 radial direction. (11) The substances included under the name of 

 cutin resemble those which are united under the name of suberin. 



(12) The presence of wax is rarer than has been formerly supposed. 



(13) Undulations may be formed in the suberous layer. (14) In many 

 cases it is not necessary to suppose that a suberification of the middle 

 lamella in the radial walls takes place. 



* Comptes Eendus, evil. (1888) pp. 402-5. 

 t Arch. Ne'erland., xxii. (1888) pp. 253-96. 



