776 SUMMARY OF CURRENT RESEARCHES RELATING TO 



. seed of many species of Papilionacege a structure hitherto known only 

 among Ferns ; for the wall of the intercellular spaces is clothed with a 

 number of filiform processes. These processes are most common in 

 the neighbourhood of the micropyle and hilum, and, when most fully 

 developed, take the form of capitate rods, or sometimes of elongated 

 filaments. The microchemical reactions of these substances are given 

 in detail ; and the authors conclude from them that these rods are identical 

 in nature with those of the Marattiacefe, and are formed of a substance 

 different from cellulose ; oi" rather, of two different substances, one of 

 which composes the mass of the process, the other its investing mem- 

 brane ; neither are they composed of protoplasm. The substance of 

 these processes, like the secretion of glands, is deposited in the cell- 

 wall and investing membrane, which latter is continuous with the 

 investing membrane of the intercellular space. 



Strengthening Apparatus in the Stem of Saxifragacese.* — M. Thou- 

 venin describes the variations in the structure of the stereome to be 

 found in tlie underground stems of Saxifragaceae, which he groups under 

 eight heads, dependent on the degree of development of the pith, cortex, 

 and medullary rays, and on the structure of the pericycle and endoderm. 



Radial Union of Vessels and Wood-parenchyme.f — Herr F. 



Gnentsch describes several different ways in which the vessels of two 

 successive annual rings unite, as well as differences in the distribution 

 of the vessels. He draws the general conclusion that the annual ring is 

 not so completely closed as is usually supposed. On the contrary, the 

 vessels, one of the most important constituents of the xylem, regularly 

 unite at the boundary of two successive rings, either directly or by 

 tracheides. Through this union a regular interchange of formative 

 material takes place, especially in the spring, when the medullary rays 

 are unable to perform this function to any large extent. The wood- 

 parenchjme-cells, on the other hand, are in general concerned only with 

 tangential and not with radial conduction. 



Formation of healing Periderm.:}: — Herr L. Kny has investigated 

 the influence of light, temperature, moisture, pressure, and other external 

 agencies on the formation of periderm which follows the infliction of 

 iDJuries on the tubers of many plants. He finds that the cell-divisions 

 which inaugurate the formation of the periderm take place indifferently 

 in diffused daylight and when light is excluded; and that the later 

 processes and the suberization in the periderm-cells are not materially 

 influenced by the amount of light. These cell-divisions are promoted 

 by a medium moisture of the air. The position of the cut surface, 

 whether facing upwards or downwards, or whether vertical or horizontal; 

 does not affect the cell-division. The free oxygen of the air is essential, 

 both for the commencement of the cell-division and for the formation of 

 cork. 



Formation and Development of Libriform Fibres. § — Herr A. Wieler 

 has investigated the phenomena connected with the development of the 

 libriform fibres in the xylem of the stem of dicotyledonous plants, 



* Bull. Soc. Bot. France, xxxvi. (1889) pp. 125-33. 



t ' Ueb. radiale Verbindungen d. Gefasse u. d. Holz-parenchyms u.s.w.,' Kegens- 

 buig, 1888. See Bot. Centralbl., xxxix. (1889) p. 34. 

 J Ber. Deutsch. Bot. Gesell., vii. (1889) pp. 1.54-68. 

 § Bot. Ztg., xlvii. (1889) pp. 517-28, 533-40, 549-61 (1 pi.). 



