260 FLORA OF LOWER COAL MEASURES OF MISSOURL 



All the material from Missouri, with the i^ossible exception of the doubt- 

 ful fragments referred to as Cordaites diversifolius f belong to the group Eucor- 

 daites of Grrand 'Eury, i. e., to the genus Cordaites restricted. 



Cordaites communis Lx. 



PI. Ill, Fig. 1; PI. XVI; PI. XLVI. 



1S78. Cordaites communis Lesquereux, Proc. Amer. Phil. Soc, vol. xvii, p. 320. 

 ISSO. Cordaites communis Lesquereux, Coal Flora, vol. ii, p. 534. 

 1893. Cordaites communis Lx., D. White, Bull. U. S. Geol. Surv., Xo. 98, p. 105. 

 1899. Cordaites communis Lx., D. White, 19tli Ann. Rept. U. S. Oeol. Surv., pt. 3, 

 p. 533. 



The species originally described from Missouri is represented in the 

 collection by numerous specimens, some of which probably come from the 

 type locality. The general form of the leaf, as seen in part in PI. XVI, is 

 spatulate. From the broadest point, in the upper part, it narrows gently to 

 the thickened base, which is slightly crescentic when compressed, and is not 

 infrequently as much as 2 cm. wide in the full-grown examples. The apex 

 of the leaves is rather broadly truncate-rounded and slightly oblique. The 

 nervation of this species, as seen from the examination of the types of the 

 species now in the Lacoe collection, is very irregular in character and 

 apparent density. Even on the same leaf it may be found composed in one 

 area, especially near the base, of moderately strong nerves close together or 

 separated by from one to three or four less prominent, or, in another area it 

 comprises distant, quite prominent nerves, perhaps 15 to 20 to the centimeter, 

 separated by from four to six smaller nerves. The difficulty of arriving at 

 a satisfactory numerical characterization of the nerves is further increased 

 by the irregular disappearance or immersion of the intermediate nerves in 

 the thick tissue of the leaf and the fine striation, perhaps due to the rows of 

 cells, which is often more conspicuous than the depressed intermediate ner- 

 vation. These rows or stride number about twelve to the millimeter in some 

 specimens. 



The inflorescence described as Cordaiantlms ovatiis Lx. belongs almost 

 certainly to this species, to which I am also disposed to refer the Cordai- 

 carpus cerasiformis as the fruit. Cordaites comviunis is, in the Missouri flora, 

 the host of Rysterites Cordaitis Grr. 'Ey., the bordered perithecise of wliich 

 are frequently found in its leaves. 



