492 



THE AMERICAN NATURALIST 



[Vol. XL 



the fossil species Comptonia laciniata, this arching of the veins 

 along the border is more or less interfered with, and a branch 

 from the nearest secondary proceeds to the tip of the tooth. 

 Where the lobes are not separated to the midrib there is usually 

 a vein of the same caliber as the secondaries which proceeds 

 directly to the sinus between the lobes, where it forks and its 

 two branches arch along the borders of the adjacent lobes on 

 each side (above and below). The finer areolation shows three-, 

 four-, or five-sided reticulations. On the whole the venation can- 

 not be said to show any especially characteristic and distinctive 

 features. The usual style of leaf is finely figured by Schimper 

 in his Traite de Paleontologie Vegetale, Plate 84, Fig. 4 (1874), 

 which is copied from a figure of Ettingshausen, in his Blattskektte 

 der Apetale. 



Reverted Form of Seedlixg Leaves 



In discussing Comptonia micro phylla I have mentioned the curi- 

 ously shaped leaves of the seedlings of the existing species, the 

 first six or seven of which are indistinguishable from those of 

 the earliest Comptonias from the INIid-Cretaceous, and which 

 are evidently true reversions. Some of these are well shown on 

 Plate 3. I have collected numerous examples of these leaves and 

 believe this form to be a constant feature of the seedling leaves, 

 furnishing admirable proof of the correct identification of their 

 Cretaceous ancestors. 



As might be expected, the various fossil species of Comptonia 

 probably had leaves on their seedlings which were similar to this 

 form. Seedling plants, as can be readily understood, are rare as 

 fossils. I am convinced, however, that the leaves which Heer ' 

 refers to Mijrica latiloha from the Miocene of Locle and Oeniii- 

 gen are to be so understood. Their form and venation are exartl v 

 that of the modern seedlinu- leaves am ! they have the same thin tex- 

 ture and thickened niidril., I.r>,,iirn-iix's Fig. 12 of Mi/rica (dka- 

 lina from the Green River i;n)U[) of Wyoming is also a young leaf, 

 probably of Comptonia insignis (Lx.) Berr}'. 



1 Heer. Fl. Tert. Helv., vol. 3, p. 176, pi. 150, fig. 12-15, 1859. 



