106 WRIGHT : THE GENUS DIOSPYROS 



leave the question of affinity until detailed information for 

 the remaining species is at hand. 



The fossil species described by Unger, Ettingshansen, 

 Massalongo, and others, the present distribution through 

 tropical regions of the eastern and western hemispheres, in 

 sub-tropical South Africa and Madagascar, and the occurrence 

 in temperate regions are suggestive of great age. The fossil 

 forms, the conspicuous differences between existing species, 

 especially between those in Ceylon, together with the pro- 

 bable early extinction by natural causes of many Ceylon 

 species, suggests the likelihood that the Ebenacese had in the 

 past a much wider distribution and a larger number of 

 species than at the present day. 



The great point of interest in connection with the Ceylon 

 species is the fact that a good artificial key for working out 

 the species can be constructed on separate characters, e.g., the 

 leaf, flower, or seedlings. The differences in leaf characters 

 are very marked. It is impossible to confuse the tough 

 large leaf of D. Moonii or D. acuta with the thin leaves of 

 D. Thwaitesii and D. montana, or with the thin hairy leaves 

 f DI pruriens. The pellucid character of the veins in 

 leaves of D. Ebenum. D. Embryqpteris, D^Toposia, and D. 

 Gardneri separates these species from one another and from 

 all other species, and questions of size and form provide 

 sufficient differences for separating the remaining species. 

 Then again we have seen that it is very convenient to group 

 the species according to their sex characters.* 



A good artificial key for the Ceylon representatives can be 

 made on the characters of the seedlings alone, the classification 

 being based on the number of traces per cotyledon, abortion 

 or persistence of the median cotyledonary traces, characters 

 of cotyledons, epicotyledonary leaves, and hypocotyl. 



The secondary xylem is the most constant structure 

 throughout the genus, and in the respective species shows 

 differences only in percentage number of the elements. 



* Sex in Diospyros. Brit. Assoc., Belfast, 1902. / 8 ' l 0^ *) 



[_To be continued in next number.] 



