OF LOWO GREEXSAVD PLANTS. 



to Tertinry in age. "While his descriptions are somewhat anti- 

 quated, his observations and illustrations are not excelled by 

 more recent work. 



Cedroxylon and Cuprftninoxylon are alike in having no 

 normal resin-canals. The older criterion of separation used 

 to be the absence of xylem-parenchyma in the former, and its 

 presence in the latter genus. It has been found, however, both 

 in living and fossil woods that even those species in which the 

 wood-parenchyma is generally absent may show some cells in 

 portions of their tissue, so that the distinction no longer holds. 

 Nevertheless, Oppress in o.rylon is still distinguished from Cedro- 

 xylon by normally having very much greater amounts of xylem- 

 parcnchyma. Mercklin (1855, pi. xii, fig. 3) and others illus- 

 trated well the minute details of the characteristic wood-paren- 

 ohyma of Cupretsino&ylon, with its approximately horizontal 

 cross-walls. 



A more reliable feature in the separation of this genus from 

 Cedro.rylon lies in the characteristic presence of " abietinean 

 pitting" in the latter genus and its normal absence in the 

 former. Some species of Juniperus, however, show typical 

 " abietinean pitting," so that the criterion is not final in all 

 cases. 



Cupressinoxylon vectense, Barber. 

 [Plate XV ; text-figs. 48, 49, 50.] 



1898. Cupressino.rylon vectense, Barber, Ann. But., vol. 12, p. 387, 

 pis. xiii, xiv. 



Diay-no&is. -Pith about '9 mm. in diameter, walls rounded, 

 pitted, with large intercellular spaces. Primary bundles entirely 

 centrifugal. Secondary wood composed of small regular tracheids 

 up to about 25 /.i in diameter. Bordered pits generally round, 

 isolated, and in one row, sometimes adjacent and the row partly 

 doubled. Tangential pits in autumn wood. Annual rings well 

 marked, conspicuous, " composite " ; some with three or four 

 irregularly amalgamated zones in each. Medullary rays mostly 

 uniseriate, a few partly biseriate ; cells all alike, walls smooth : 

 pits in radial walls 1-2 per tracheid-field ; each pit smallish 

 and irregularly oval or round, llesin-parenchyma abundant, 

 scattered all through the wood, with approximately rectangular 

 cross- walls. 



