ENGELMANN — OAKS OF THE UNITED STATES. 541 



are cordate or obtuse at base, and almost all deeply runcinate-serrate. — 

 This instance ought to make us very careful not too hastily to judge of the 

 parents of a hybrid from the species growing nearest to it. 



Q. Phellos y^coccitiea, Q. heterofhylla, Michx., is distinguished bv the 

 petioled leaves of lanceolate outline, entire, sinuate, spinulose-dentate, 

 coarsely serrate, or with simple, sometimes spreading or falcate, lobes ; 

 leaves of different form on the same tree and often on the same branch, 

 the uppermost leaves usually entire;* or some trees more with entire, 

 others more with dentate or with lobed leaves. Youngest leaves strongly 

 revolute, pubescent above, white-downy below, becoming glabrous in sum- 

 mer. Acorns subglobose to oval, 5-7 lines long, a little less wide, scarcely 

 half immersed in the shallow-hemispherical, somewhat turbinate, canes- 

 cent cups; scales lanceolate, obtuse. Fruit of same size and very similar 

 to that of falcata, but cup usually deeper and with larger scales. 



The typical specimen described by Michaux, found by him "in a field 

 belonging to Mr. Bartram near Philadelphia," has long since been de- 

 stroyed, but its offspring was introduced into Europe, and the trees now 

 seen in Bartram's garden in West Philadelphia, at Marshall's place in 

 Marshalltown, and in J. Hoopes' garden in Westchester, as well as those 

 of the European gardens at Verriere, Herrnhausen and Prague, the latter 

 fertile, are believed to be its seedlings. Only within the last ten or fifteen 

 years the tree has been re-discovered, and now numbers of individuals are 

 known in low woods on both sides of the Delaware below Philadelphia 

 (6 miles east of Camden, Smith, Leidy, Burk, Martindale, and 2 miles 

 west of Wilmington, Commons. Canby), often in groups together, probably 

 the offspring of some few original hybrid trees. 



A. DeCandolle and others viewed this hybrid as a form of aquatica 

 others as belonging to Phellos, while I was long inclined to follow Michaux 

 in considering it as a distinct species. With aquatica, which does not grow 

 within a hundred miles, it has no relationship ; aside from other charac- 

 ters, the revolute vernation abundantly distinguishes it from that species; 

 from Phellos it differs in the form and size of the leaves and their thick 

 down in youth (in Phellos even the youngest leaves are almost glabrous), 

 and in the larger acorn in a deeper cup bearing much larger and longer 

 scales. That it is a hybrid is most probable on account of its great rarity 

 and its so very variable foliage. One of its parents is undoubtedly Phel- 

 los; for the other we must look among the lobe-leaved Black-oaks of its 

 neighborhood, falcata, rubra or coccinca. While the sometimes falcate 

 lobes of the hybrid and the similarity of its acorns point to the first, and 

 its frequency in those localities to the second, we find the texture of the 

 leaf and its reticulation as well as size and form of the cup and its scales 

 intermediate between Phellos and tinctoria, and quite different from the 



* This is the case generally in heterophyllous hybrids, i.e. hybrids between entire-leaved 

 and lobe-leaved species ; the uppermost leaves of an axis are apt to be entire, while the 

 middle ones are lobed, etc. ; thus the lower branches also often bear entire leaves, while the 

 upper ones have more lobed ones. 



