OF LOWER GREEXSAND PLANTS. 



and, locally, rather irregularly arranged tracheids which vary 

 very much both in size and shape even in adjacent elements 

 (see text-fig. 51). The larger and more regularly arranged 

 tracheids average about 30 x 40-40 x 50 p. Even in the first- 

 formed spring wood the walls are rather thickened, and measure 

 about 3-5 fi. The autumn wood measures 12 /x in radial 

 diameter as a rule, the lumen of the cell often being narrower 

 than the walls. Pits in the radial walls are often visible in 

 transverse section, and in radial section are seen to be principally 



mw. 



Text-fig. 52. Cupressitoxylon lucconilfense, sp. nov. Radial longitudinal 

 section showing tracheids, t i ; a tracheid with -the bordered pits 

 adjacent, t % ; rp., resin-containing wood-parenchyma ; mw., the medul- 

 lary ray-cells with curved end-walls ; mp., the groups of irregular 

 roundish pits per tracheid-field. [Slide SD. c, Stopes coll.] 



in one row. A few irregular double rows may be detected. 

 As a rule, the round bordered pits are separate from each other, 

 a few may lie in adjacent rows (text-fig. 52, t 2). 



Wood-parencliynia is common all through the wood. The 

 horizontal walls in both tangential and radial sections are 

 rectangular (text-figs. 52 &, 5.'i, rp.). In the radial direction 



