'6 T. D. A. Cocker ell — Descriptions of Tertiary Plants. 



Art. YII. — Descriptions of Tertiary Plants, III ; by 



T. D. A. CoCKERELL. 

 A SORBUS FROM FLORISSANT, CONSIDERED TO BE A HYBRID. 



Sorbus diversifolia (Lx.), fig. 1. 



Myrica diversifolia Lx., Cret. and Tert. Flora (1883), p. 148, pi. 

 xxv, f. 6 (not Crataegus diversifolia Steud.; not Pyrus diver- 

 sifolia Bong.). 



Cratmgus acerifolia Lx., Cret. and Tert. Flora, p. 198, pi. xxxvi, 

 f. 10 (not C. acerifolia Moench). 



Cratmgus lesquereuxi Ckll., Bull. Ton*. Hot. Club, 33 (1906), p. 

 311 (not Sorbus lesquereuxii Nath.). 



Onoclea reducta Ckll., Bull. Am. Mus. Nat. Hist., 24 (1908), p. 76 

 and 108, pi. vi, f. 4. 



The extraordinarily variable plant to which the above names 

 have been applied is quite common in the Miocene shales of 

 Florissant, at Station 14. A good leaf was also found by my 

 wife at Station 20. In Knowlton's Catalogue (Bull. U. S. 

 Geol. Surv. No. 152) Myrica diversifolia is referred as a 

 synonym to Crataegus flavescens Newberry (newberryi Ckll.) ; 

 but in his Fossil Flora of the John Day Basin, p. 66, Dr. 

 Knowlton recognizes that while the John Day specimen 

 referred to Myrica diversifolia by Lesquereux is undoubtedly 

 C. flavescens, the Florissant specimens are doubtfully identical. 

 There occurs at Florissant (Station 14, W. P. Cockerell), a 

 species of Crataegus which I have provisionally referred to 

 C. newberryi, although the leaf is less deeply lobed, and it is 

 not unlikely that the plant is distinct. This, however, has 

 nothing to do with the true Myrica diversifolia, which is 

 evidently identical with Crataegus lesquereuxi. A comparison 

 of numerous specimens had convinced me that this well-named 

 " diversifolia " was a Pyrus in the broad sense, and probably 

 a Sorbus; but I possessed no material exactly comparable, 

 although I distinctly remembered having seen a similar living 

 plant. During the past summer I was permitted to gather 

 leaves in Kew Gardens, and there at length I found what I had 

 been looking for, labelled Pyrus pinncttjflda var. fastigiata, 

 and Pyrus neuillyensis. These trees are hybrids between the 

 Aucuparia and Aria sections of Sorbus. P. pinnatifida 

 Eh rh. is properly called Soi'bus liybrida Linne. It has the 

 apical half of the leaf like Sorbus intermedia Pers. {Pyrus 

 intermedia Ehrh.), while the basal half is variably cut into 

 leaflets in the manner of the Aucup aria group. This occurs 

 in Europe as a natural hybrid (intermedia X aucuparia). 



