174 COBB— RELATIONSHIPS OF WHITE OAKS [April 23. 



Key to Deciduous White Oaks of Eastern North America. 



Leaves deciduous, lobed or dentate, not spinulose. 

 I. Leaves lobed. 



A. Stipules persistent; buds more or less acute. 



1. Twigs slender, smooth. Lyrata. 



2. Twigs stout, pubescent. 



a. Fruit sessile, larger; cup usually deeper and fringed. 



Macro car pa. 



b. Fruit pedunculate, smaller ; cup more shallow, seldom fringed. 



Bicolor. 



B. Stipules deciduous ; buds rounded. 



1. Twigs smooth. Alba. 



2. Twigs pubescent. 



a. Leaves deeply five-lobed, pubescent below. Minor. 



b. Leaves undulate, glabrous below Chapmani. 

 II. Leaves dentate. 



A. Buds less elongate, leaves narrower, widest near middle. Muhlenbergii. 



B. Buds more elongate, leaves broader, widest above middle. 



1. Cup scales free at tips only; upper scales very small. Prinus. 



2. Cup scales free; upper scales often forming a fringe to cup. 



Michauxii. 



Description of Plates. 



Plate IV. Buds of the rounded type, without stipules. X 3- 



Fig. i. Q. alba (Urbana, Illinois). 



Fig. 2. Q. minor (collected by H. H. Bartlett, Maryland). 



Plate V. Buds of the more acute type, stipules persistent. X 3- 



Fig. I. Q. tnacrocarpa (Urbana, Illinois). 



Fig. 2. Q. bicolor (Urbana, Illinois). 



Plate VI. Buds of the elongated, chestnut oak type. X 3- 



Fig. I. Q. prinus (collected by H. H. Bartlett, Maryland). 



