1907] MACDOUGAL—HYBRIDIZATION OF WILD PLANTS ey 
identifying any of the forms with those of Q. rubra. It is to be noted, 
however, that as a result of the consideration of gross anatomical 
facts and distributional data, Dr. Horzick and other botanists had 
finally concurred in the general conclusion that the tree was in all 
probability a hybrid between the red oak and the willow oak. 
; Fic. 2.—Plantlets from progeny of tree of Q. heterophylla which bore leaves as 
In fig. 1,C. I bears leaves not distinguishable from those of Q. Phellos, and VI resem- 
bles Q. rubra. II, III, IV, and V form a series between J and VJ.—Photographed 
April 1906. 
lel to those shown 
_ _ Fic. 3.—Series of leaves from progeny of Q. heterophylla, paral 
In fig. 2, but taken at the close of the season of 1906. 
With our present available information concerning the behavior 
of hybrids this conclusion seems unavoidable. If we attempt to 
follow out the history of the hybridization as it may have occurred, 
Owever, we are compelled to rely upon inference in part. The 
