6 WRIGHT: THE GENUS DIOSPYROS 



the axis was more thoroughly dealt with, and a theory was 

 set forth explaining the enhanced durability of ebony as a 

 consequence of the walls of the elements being impregnated 

 with a colouring substance of unknown chemical constitu- 

 tion. 



A much more instructive paper was then issued by 

 ; / ,, Molisch,* who prepared his sections by the method of 

 Wiesner. Molisch described the anatomy of the stem of 

 two of our species, D. Ebenum, Koen^ and D. sylvatica, Roxb., 

 together with three others, and a species from each of the 

 genera Maba, Euclea, and Royena. He attempted to combine 

 the facts of internal construction with external morphology, 

 believing with Radlkofer that this would provide the best 

 basis for a systematic grouping of the plants. He also laid 

 stress on the striking anatomical resemblances of the species 

 he examined, and endeavoured to discover whether the 

 reason of the high technical value of the ebony woods lay 

 in the anatomical construction or in the chemical changes 

 going on within the tissues. 



In connection with the colouring matter of the timbers, 

 he believed that the initial deposits were true gums, and 

 that the suspected resin was a product of a slow process of 

 humification going on within the elements. He further 

 endeavoured to show that seasonal rings of growth were 

 found in the secondary xylem of trees of D. Virginiana, Z,., 

 which had been grown in Europe, whereas those grown 

 in the tropics showed no such histological differentiation. 

 The various points raised by Molisch will be subsequently 

 discussed under their respective sections in the present 

 contribution. 



Hartigf has given an account of the timber of several 

 species, and has discussed the views of Moeller and Molisch 

 as to the nature of the colouring substance in ebony. He 



* H. Moliaeh, Vergleichende Anat. des Holies der Ebenaceen nnd ihrer 

 Verwandten. Site. Akad. Wiss. zn Wien, Bd. 80, Abth. 1, 1879. 



t Hartig, Bot. Ztg., p. 108, 1859, and also Lehrbnch fur Fotster. I. TheiL 

 p. 256, 1861. 



