ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 447 



(3) The tannin which is found in the heart-wood appears to he 

 formed by the transformation of starch. 



(4) Whenever an accumulation of starch is found in a woody tissue, 

 it is either because the migration of this substance has been stopped, or 

 because there is in the tissue an excess in quantity beyond the use tbat 

 can be made of it. 



(5) Tannin oxidizes on contact with air, and the colour is deepened. 



(6) This oxidation of the tannin contained in the wood proceeds 

 spontaneously, following the growth in age of the tree. 



Diaphragms in the Air-canals of the Root.* — M. C. Sauvageau 

 states that vascular plants which live in damp places or in water nearly 

 always possess air-canals intercepted by transverse diaphragms situated 

 in the middle region of the cortex ; only, until the present time, the air- 

 canals of the root were supposed to be destitute of these diaphragms. 



In the course of a series of researches on the comparative anatomy of 

 aquatic plants, the author found, in the root of Hydrocliaris morsus-ranse, 

 diaphragms similar to those in other parts of the plant. The lacunaB or 

 air-canals are parallel to one another throughout the length of the root ; 

 the diaphragms, which can be seen in either a transverse or longitudinal 

 section, are sometimes oblique to the direction of the root, but more often 

 they are at right angles to it. 



Oil-passages in the Roots of Compositse.f — Herr Triebel finds oil- 

 passages in the roots of thirty-one species of Composita) examined 

 belonging to the groups Cynareaa and Kadiatfe. They are always of 

 schizogenous origin, resulting from tangential division of the endoderm, 

 with which they usually continue in direct contact. In Inula Helenium 

 similar structures occur in the middle of the root. 



Effects produced by the Annular Decortication of Trees.!— M. H. 

 Lecomte states that the annular decortication of trees brings about 

 several important changes in the manner of growth. The stem, the 

 leaves, and the fruit are made by this mutilation the seat of an ex- 

 aggerated development ; the liber also grows more strongly in proportion 

 to the other tissues, and there can be no doubt that decortication, while 

 suspending the passage of substances elaborated in the green organs, 

 produces hypertrophy of the upper parts, and causes an arrest in the 

 development of organs situated below the mutilation. 



Systematic Value of the Perforation in the Walls of Vessels.§ — 

 Dr. Solereder discusses the value of the different modes of perforation of 

 the walls of true vessels and of tracheides from a systematic and 

 phylogenetic point of view. 



The tracheides of the Vascular Cryptogams exhibit what must be 

 regarded as the primary type of perforation, viz. that with scalariform 

 pits. True vessels occur only in a few isolated cases in Vascular 

 Cryptogams. In Gymnosperms they are confined to a single order, the 

 Gnetaceae. In almost all Coniferaa and in Cycadeaa, the xylem consists 

 entirely of tracheides; the medullary rays and the phloem of the 



* Comptes Eendus, cvi. (1888) pp. 78-9. 



t Nov. Act. K. Leop.-Carol. Akad., 1. (1887) 32 pp, See Bot. Centralbl., xxxiii. 

 (1888) p. 201. 



X Morot's Journ. de Bot., i. (1887) pp. 266-70, 273-8. 



§ Bot. Ver. Miinchen, March 21, 1887. See Bot. Centralbl., xxxiii. (1888) 

 p. 315. f 



