OF LOWER GREENLAND PLANTS. 



151 



DETAILS OP ELEMENTS. Owing to the smallness of the narrow 

 bands of autumn wood, the mass of the wood consists of traclieids 

 the si/e of the spring wood, which averages about 40-50 fj. by 

 50-80 ju, with comparatively thin walls. The one or two rows 

 of narrow autumn elements are about 50 /j, X 15^, with walls as 

 thick as the lumen or with the lumen reduced to a mere slit 

 (text-fig. 41). In transverse section, bordered pits are evident in 

 many of the radial tracheid-walls ; those tracheids adjacent to 



Text-fig, 42. Cedroxylon maidstonense, sp. nov. Tangential section of 

 medullary ray, showing the uniformly thick-walled cells, p.e., showing 

 a pitted end-wall. Notice that the ray is partly biseriate. No. 1769 b. 



the medullary rays show several small pits in one wall (text- 

 fig. 41, p.t.\ I have detected pits in the tangential walls of only 

 a few of the autumn wood-elements. In radial view the tracheid- 

 pits are round, the border being only half, or less, of the diameter 

 of the tracheid. The pits are in a single row, separated by their 



