626 
BOTANY: W. TRELEASE 
compound may be correlated with the abihty of this element to act 
as it does in Grignard's reaction, as has been suggested by Willstatter." 
The relatively greater toxicity of potassium over sodium, as in Loeb's 
experiments with Fundulus, may be ascribed to selective absorption or 
membrane permeability. The connection between these pairs of ele- 
ments in magmas and minerals may be ascribed to differences in solu- 
bility. 
Each one of these or other such explanations, taken individually and 
separately, may be rational and valid; but taken collectively, espe- 
cially in view of the congruity of the four elements in the mineral and or- 
ganic kingdoms, they make it appear possible and indeed reasonable to 
ascribe the correspondence to some fundamental chemical relation be- 
tween the elements involved, of which such proximate causal nexuses as 
have been suggested are the consequences. No hypothesis can be of- 
fered as to what may be the nature of this relation; only the mere pos- 
sibility of its existence, based on the correspondences set forth in this 
and the preceding paper, can be suggested. 
iR. S. Washington, these Proceedings, 1, 574 (1915). 
2 Cf. Reichert and Brown, Carnegie Inst. PubL, No. 116, 24 (1909). 
^O. Hamarsten (Transl. by Mandel), Textbook of Physiological Chemistry, p. 564 (1900). 
^ Cf. S. B. Schryver, Scieitce Progress, 3, 440 (1909). 
^ Reichert and Brown, op. cit., 1; Schryver, op. cit., 444. 
« E. Strasburger et al. (transl. by Porter), Text-book of Botany, 173 (1898). 
' Cf. J. Loeb these Proceedings, 1, 473 (1915); 2, 511 (1916). 
^ It is suggested that the lesser toxicity of the ferric salts may be ascribed to their ready 
hydrolysis and the consequent formation of very difficultly soluble basic compounds. 
9 Op. cit., 2. 
Copper, likewise with two valencies, exists in the blood of certain lower animals, as 
moUusca, limulus, helix and sepia. 
11 The dependence of plant life on magnesium and of animal life on iron, and the differ- 
ence in their functions, is expressed by Willstatter as follows: "There are fundamentally 
two kinds of life, which develop alongside of each other: the anabolic life with magnesium 
and the katabolic life (of animals) with iron, that is a reducing and an oxidizing life." See 
Liehig's Ann. Chem., 250, 65 (1906). 
THE OAKS OF AMERICA 
By William Trelease 
DEPARTMENT OF BOTANY. UNIVERSITY OF ILLINOIS 
Received by the Academy, October 13, 1916 
For a number of years I have been engaged in a study of the oaks of 
tropical America. These have not been treated comparatively for a 
generation, with the result that the extensive collections made within 
that time have gone into herbaria largely unnamed or wrongly named. 
