IN CEYLON. 21 



Diospyros genus. The leaf production is apparently not of 

 such a nature as to severely tax the resources of the plant, 

 and its occurrence is probably to be correlated with indivi- 

 dual requirements rather than with climatic conditions. 



This can only obtain in the vegetation of the tropics 

 where the temperature and rainfall are relatively equable 

 throughout the year. 



IV. ANATOMY, TIMBER, &c. /^^ l ~ 



Stem. In the genus Diospyros the phellogen is often 

 said to be of sub-epidermal origin, and this is considered by 

 Parmentier and Solereder to be of taxonomic importance, 

 the former using this as one of the main characters in his 

 proposed grouping of the genera. The phellogen, however, 

 actually arises either immediately beneath the epidermis or 

 from the pericycle, the latter origin being conspicuous in the 

 primary axis or hypocotyl of the seedlings. 



The sclerotic or stone cells of the cortex are conspicuous 

 in D. Ebenum, and the various stages of their formation and 

 degeneration are shown. (See pi. XIX., figs. 1-4) ; they are 

 relatively short, thick walled, and well pitted ; finally they 

 lose their definite outline and form hyaline masses of tissue, 

 which do not respond to the commoner staining reagents. 

 In longitudinal section they are seen to be surrounded with 

 parenchyma and long sclerenchymatous fibres. The phloem 

 and cambium are of the ordinary type, and we may proceed 

 to deal with the anatomy of the secondary xylem. 



The observations of Molisch, Holier, Solereder, and ot^/jc U 

 Parmentier, already referred to, all agree as to the regular 

 composition of the secondary xylem, the scarcity of tracheids, 

 and the distribution of the elements. 



Molisch obtained his sections of the hard brittle ebony by 

 the method of Wiesner, which is briefly as follows : A thin 

 slip of ebony, 2 to 3 cm. square, is cut by a fret-saw and 

 fastened by means of sealing wax to a cork ; both sides of 

 the section are then polished on a smooth rotating wheel, 



