406 BOTANICAL GAZETTE [DECEMBER 
between the leaves of different trees, and even the leaves unequally 
exposed on the same.tree; which naturally makes him skeptical of 
the value of determinations of extinct oaks by the remains of their 
leaves. The variations independent of the direct action of the 
environment, which I have just depicted, must strengthen the skepti- 
cism. 
Before leaving the subject of Quercus I wish to discuss briefly 
BRENNER’S conclusions. He regards the less stability of the lobed 
forms of leaf as compared with the entire as evidence of the greater 
antiquity of the latter; such a difference in their variability—which 
should be a better test of newness than stability under varying environ- 
ment—does not exist in this region. Still, considering oaks the world 
over, BRENNER may well be correct on this point. In his concluding 
paragraph, however, he exposes a classical weakness which needs 
pointing out as often as it occurs. It reads: 
Was als wichtigstes Ergebnis aus derartigen Untersuchungen hervorgehen 
diirfte, ist die so oft noch bezweifelte Thatsache, dass die durch dussere Medien 
hervorgerufenen Veriinderungen an den Pflanzen thatsichlich erblich werden 
und im Lauf der Entwickelung zu eigentlichen Artmerkmalen sich entwickeln 
kénnen. Durch den Nachweis, dass bei den Eichenblittern die Veranderungen 
beim Versuch und bei natiirlichen Standortsunterschieden den mit dem Klima 
wechselnden Speziesverschiedenheiten entsprechen, hoffe ich einen Theil zur 
Kriftigung dieser Anschauung beigetragen zu haben. 
If one accepts the inheritance of acquired characters 4 priori as 
““Thatsache,” he may construe BRENNER’S observations as an illus- 
tration of it. But the direct reaction to the environment is fairly to 
be regarded as the result of natural selection, developed and pre- 
served by virtue of its appropriateness; and since it is appropriate, 
it is obvious that by natural selection alone the plants varying in this 
direction spontaneously would be at an advantage, and in the long 
run would be parents of all the offspring. Since the identity of the 
forms assumed as a direct response to the environment with the forms 
characteristic of lands with the corresponding climate is fully expli- 
cable by natural selection alone, it is certainly no valid argument 19 
favor of the inheritance of direct reactions to the environment. 
My oak leaves will be discussed with those of the other woody 
plants. 
