OF BUCKLEYA QÜADRIALA, B. ET H. 27 



medullary rays in the cortical and axial parts, their function 

 as the reservoir, and also as the way of conduction, of nutritive 

 substance (mainly carbohydrate) at certain times, becomes quite 

 evident. 



5. The Annual Rings and the Formation of 

 the Duramen. 



In the stem as well as in the root of Buckley a we can 

 distinguish the annual rings very clearly, though in the latter 

 they are somewhat irregular and sometimes somewhat obscure. 1 } 

 As regards the haustorium the arrangement and structure of 

 elements do not go so far as to make clear the difference of 

 spring and autumn wood. Yet we can faintly recognize alter- 

 nate zones of denser and less dense regions ; a demarkation 

 between the two is scarcely observable under the microscope of 

 high power, but is visible to the naked eye as an obscure line 

 (Fig. 20). 



Of these zones, the denser are formed of vessels with lumen 

 which is radially narrower than that of vessels of the other zone ; 

 while between the vessels of both zones there is no noticeable 

 difference in the thickness of the cell-wall, as is usually the 

 ease. 



When the haustorium attains a sufficient thickness, we can 

 observe in the successive zones of growth or annual rings, the 

 differentiation into the alburnum (younger rings) and the duramen 

 (older rings). Externally the two parts are distinguished by their 



1). Solms-Laubach (loc. cit. p. 539) has given as a general remark on the structure of 

 the Santalaceous plants, " Seine (Holz) Jahrringe sind äusserst undeutlich." Chatin (loc. cit.) 

 however has already shown clearly the annual rings in the stem of B. distichophylla. 



