PLANTS FROM ALASKA. 169 



palmata Heer and figured in his paper, pi. xvi, fig. 5. It, however, 

 shows no trace of a division of the lamina of the leaf. The other, given 

 in PL XLIV, Fig. 3, was obtained by Mr. Dumars. Both give the basal 

 parts with a portion of the petiole. These leaves lack their terminal 

 parts. They narrow gradually to a wedge-shaped base and expand to 

 a fan shape in the opposite direction. They show no division of the 

 lamina in the parts preserved, but may higher up have been palmately 

 divided. The base, in its prolonged wedge shape, differs from the 

 Ginkgo leaves associated with these forms, but the principal difference 

 is in the nerves. These are shown with some distinctness in PL XLIV, 

 Fig. 3. Fig. 4 shows the nature of the nerves. The margins are thick- 

 ened to form a parent nerve that sends off, very obliquely, secondary 

 nerves that enter the lamina of the leaf. They fork at their insertions 

 and then are mostly single. Occasionally at long intervals a second 

 forking occurs, but this is very rare. The branches are approximately 

 parallel, diverging slightly in ascending in the leaf. They are quite 

 strong. The nerves of the central part of the leaf ascend from the top 

 of the petiole. In many respects these leaves are like the genus Ginkgo- 

 dium, established by Yokoyama for certain forms from the Jurassic of 

 Japan." But the Japanese plants have slender nerves that do not fork 

 at all. They go off from the marginal nerve straight to the summit 

 of the leaf and are parallel to the axis of the leaf. As, however, Yoko- 

 yama found only one species, it is possible that the limits of variation 

 of the genus may include the Alaskan species. 



This fossil resembles also the forms described from the Permian 

 of southwest Pennsylvania and West Virginia as Saportsea.'' This has 

 the marginal nerves and the branching lateral ones, but the differences 

 are too great to permit these leaves to be placed in that genus. The 

 material is so imperfect and small in amount that the Alaskan fossil 

 can not be positively identified with Ginkgodium. 



a Jurassic plants from Kaga.etc: Jour. Coll. Sci. Imp. Univ. Japan, Vol. III,Pt. I, pp. 56-58, pl.ii,fig 4e; 

 pi. iii, fig. 7; pi. viii; pi. ix, figs. 1-10, 10a; pi. xii, figs. 14, 15. 



b The Permian or Upper Carboniferous flora of West Virginia, b3' Wm. M. Fontaine and I. C. White: Second 

 Geol. Survey Pennsylvania, Report of Progress, PP, 1880, pp. 99-103, pi. xxxviii, figs. 1-4. 



