6 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1!»22. 



Goniopteris, of which then' is a very characteris- 

 tic form in the Claiborne. 6 The dryopterids are 

 widely distributed and mainly tropical, although 

 Christensen's subgenus Eudryoptt ris, with about 

 100 species, is largely confined to the North 

 Temperate Zone. 



Occurrence: Goss pit, half a mile east of 

 Mansfield, De Soto Parish, La.; collected by 

 O. M. Ball. 



Genus ACROSTICHTJM Linne. 

 Acrostichum sp. 



This characteristic fern genus is represented 

 in the Wilcox by a single fragment, too small 

 for determination or description but showing 

 the areolation of this genus. It is a strand 

 type well represented in the Claiborne, Jack- 

 son, and Catahoula of the embayment area, 

 and its unaccountable absence among the 

 strand types in the Wilcox was the occasion 

 for comment in the former discussions of this 

 flora. The present fragment adds this in- 

 teresting type to the Wilcox flora and raises 

 the number of fern species known in this 

 flora to eight. 



Occurrence: Carrizo sandstone, half a mile 

 west of Carrizo Springs, Dimmit County, Tex. 



Phylum CONIFEROPHYTA. 



Order PDJALES. 



Family TAXODIACEAE. 



Genus CUPRESSINOXYLON Goeppert. 



[Monographic der fossilen Coniferen, p. 196, 1850.] 



Conif erous wood composed of tracheids and xylem paren- 

 chyma only. In the tracheid walls the pits are generally 

 round, bordered, and isolated, in one row; if in two rows 

 the pits stand in adjacent pairs and are not alternating or 



c pressed. Sanio's rims often conspicuous. Normal 



resin canals entirely absent. Resin containing xylem 

 parenchyma present, generally in large quantities, and 

 scattered all through the wood. Medullary rays unise- 

 riate; a few may be partly biseriate. The cells of the rays 

 all alike, generally smooth-walled, and without abietinean 

 pitliii'_ r i which is pp'H-iii in a lew species i; pits in the radial 

 walls of the rays generally circular or oval, simple, small, 

 and in groups of one to six, seldom more, per tracheid 

 field.' 



Cupressinoxylon wilcoxense Berry, n. sp. 

 Plates I -1 11 



Trunks, many of them of large size, prere- 

 senting this species are extremely common in 



■ v, E.W.,TorreyBot.Club Bull., vol. tl. pp. 331-335, pi. 22, 1917. 

 ' Stopes, M. C, The Cretaceous flora: British Mils, Cat., pt.2 , p. 167, 

 191.5. 



the upper Wilcox sands of Louisiana. They 

 have in general suffered much from decay be- 

 fore silieilication, but some specimens are ex- 

 ceedingly- well preserved. They are remarkable 

 chiefly for the great variation in the width of 

 the zone of spring wood and the well-marked or 

 almost complete absence of summer wood. 

 Thus in the sections figured the zone of spring 

 wood ranges from 5 or 6 radial rows of tracheids 

 to 23 or 24 rows, while the summer wood con- 

 sists of 3 or 4 rows. In other specimens, no- 

 tably two (Nos. 206, 211) from the vicinity of 

 Naborton, La., the spring wood consists of 45 to 

 70 radial rows of tracheids of uniform size sepa- 

 rated by r two rows of summer wood in which 

 the size of the tracheids or the cell lumen is so 

 slightly reduced that a seasonal change is 

 scarcely marked. These woods all come from 

 the same horizon, and their variation can not 

 be explained by the well-known differences in 

 the annual rings of upland and lowland forms 

 of the same species of conifers, for it is known 

 that the Wilcox land surface was low, the near- 

 est uplands at that time being in the Rocky 

 Mountain region. It is of course possible that 

 the present species extended its range westward 

 through Colorado and that some of these large 

 trunks may have been brought down from the 

 west by river floods, for at the present time 

 Red River reaches nearly to the New Mexico 

 boundary, and the headwaters of Arkansas 

 River reach the foothills of the Sangre de 

 Cristo Mountains and the Front Range in 

 central and southern Colorado. In general the 

 best-preserved material shows the narrower 

 and more marked growth rings, but both types 

 are found in all stages of decay, so that no 

 reliable conclusions can be drawn. 



Transverse section: Growth rings feebly de- 

 veloped or well marked, variable in width in 

 individual specimens. Spring wood of rela- 

 tively huge, thin-walled, mostly isodiametric 

 tracheids and xylem parenchyma, the two 

 elements not distinguishable in this section, 

 arranged in radial rows of 5 to 70 cells, aver- 

 aging 10 or 12. Cell outlines round with 

 wide lumen; diameter variable for different 

 radial rows but in general uniform for each 

 row, ranging from 0.025 to 0.975 millimeter. 

 Summer wood consisting of two to four rows of 

 somewhat reduced tracheids with narrower 

 lumen or in some specimens scarcely reduced 



