IN CEYLON. 5 



thirty-three species; and since they are not represented in the 

 flora of Ceylon, they need not be considered here. 



The Brazilian genus Brachynema, Benth., and the Javanese 

 Drebbelia, ZolL, are regarded by Hiern and others as being 

 non-Ebenaceous, and as probably of Olacinaceous affinity. 



The five genera recognized by Hiern are so closely asso- 

 ciated with one another that many botanists have suggested 

 the advisability of uniting all into one genus. 



Hiern bases his classification of the genera mainly on the 

 sex of the flowers, having the genus Royena with hermaphro- 

 dite or rarely subdioecious flowers ; the remaining genera, 

 including Diospyros, with dioecious or rarely polygamous 

 flowers. The observations were made upon material from 

 the recognized herbaria of Europe, and a small quantity of 

 spirit material obtained from Dr. Thwaites, Ceylon. 



As will be shown later, the sex of the Ceylon species 

 of Diospyros has been imperfectly and often erroneously 

 described as a consequence of examining only herbarium 

 specimens instead of the fresh material in the jungle. 



The effect of Hiern's admirable monograph is well seen 

 if one considers the history of the development of our 

 knowledge prior and subsequent to its publication. Since 

 1873 but little has been contributed to our systematic 

 knowledge of the Ebenaces, and from that time the ana- 

 tomists have been at work on the basis laid down in Hiern's 

 monograph. Their investigations have resulted in more 

 definite knowledge regarding the structure of the leaves, the 

 secondary tissues of the stem, and the nature of the causes 

 leading to the discolouration of the timbers. 



Wiesner* described the internal characters of the stems of 

 some Ceylon species of Diospyros, and gave details of an 

 onerous method of preparing sections of ebony, which was 

 subsequently adopted by Molisch. His work was succeeded 

 by contributions from Moeller,f in which the anatomy of 



* Wiesner, Ebenholz, 1870. 



t Moeller, Holzanat., in Denkschr. Wieper Akad., 1870-3. 



