ENGELMANN OAKS OF THE UNITED STATES. 39I 



has been collected on Seneca Lake in Western New-York ; it is unknown 

 in the Mississippi Valley proper. — The leaves are thick, often almost cori- 

 aceous, pale below with a short and close pubescence, obovate to lanceo- 

 late, sometimes even acuminate, those of the lower branches of the tree 

 often much wider and larger than the leaves of the upper, fertile branches; 

 teeth coarse and regular, obtuse, rarely larger, or occasionally almost ob- 

 literated in the sinuate margin; the lateral nerves usually terminate above 

 the most prominent part of the shallower teeth, and even in the sin us and 

 only in the most prominent teeth at their apex. Fruit short-peduncled ; cu p 

 deep, somewhat turbinate, tubercled — rough, as the descriptions express 

 it; base of the scales often raised in two knobs, between which the sho rt 

 and almost indistinct tip of the scale next below is almost buried : acorn 

 large, sometimes i-il inches long and 1 inch thick. 



Q. Miihlenbergii,* Q. castanea, Miihl. ap. Willd., J£. Printis acuminata 

 Michx., occurs scatteringly throughout the middle and northern Atlantic 

 States, in Pennsylvania only on limestone soil {Porter)., but its proper home 

 is the Mississippi Valley, where it entirely supplants «^>. Pri?ius, more com- 

 monly on limestone hills and ridges, but also abundantly in river bottoms. 

 Its flaky, pale ash-colored, thin bark and very tough wood (light yellowish 

 brown when mature, whence probaby the popular name of "Yellow-oak") 

 distinguish it at once from Prinus, as do also the small globose or common- 

 ly ovate acorns in a subsessile, shallow and thin cup covered with small 

 canescent, obtusish, rarely much thickened, scales. Leaves on petioles 

 f-i or even i\ inches long, thinner, more membranaceous, below pale and 

 with an inconspicuous down, usually sharper serrate, often with inflexed 

 teeth, and either lanceolate with a long acumination, 5-6 inches long by 

 l£-2 in width (the typical form of Michaux and Muhlenberg) or larger, 

 sometimes even in fertile specimens as much as 7 inches long and 5 wide, 

 broadly ovate or obovate with more rounded teeth, which form has often 

 been taken for ^>. Prinus, but is in bark and fruit identical with the 

 narrow-leaved form. 



^. prinoides, Willd., distinguished from the last by its low stature, 

 smaller, more undulate than sharp-toothed leaves on shorter (\-\ inch 

 long) petioles, and commonly by deeper cups with more tumid scales, is 

 apparently well enough marked eastward, but westward, from Western 

 Missouri to Kansas and Nebraska, where it abundantly bears when only 

 1-3 or up to 30 feet high (E. Hall, G. C. Broad/iead), it runs into the 

 arborescent Miihlenbergii. It is suggested that annual prairie fires are the 

 main cause of the stunted growth of this low form (while other species 

 are not affected in this manner), and that often large and knobby root- 

 stocks are found to produce numerous shoots, fertile in the first season. 

 Prof. Gray informs me that Muhlenberg, in his manuscript Florula Lan- 

 castriensis, considers this form a variety of his castanea ; he enumerates 



* As Muhlenberg's as well as Michaux's names for this very distinct species are preoc. 

 cupied, it seems fit to commemorate the celebrated Pennsylvanian botanist's name by this 

 oak which he had so well distinguished. 



