386 BOTANICAL GAZETTE [NOVEMBER 
potential limit of variation; the supposed direct adaptation is in reality nothing 
new, but rather the manifestation or release of a hitherto latent property. The 
new habitat is merely empirically new. Consequently DETTOo agrees with KLeBs 
that a species should not be defined as it exists normally in nature, but should 
include all possible variations in all imaginable conditions. The capacity of an 
organism is not widened but demonstrated by environmental changes. Direct 
adaptation or ecogenesis is impossible because it implies that there is a setting 
aside of the constitutionally prescribed effect of a given stimulus in the interest 
of the organism, or that menacing factors are in reality beneficial. The direct 
adaptationist conceives of a vital mechanism that looks out for the future, and holds 
advantageous reactions in readiness for conditions which have never yet occurred! 
Ecogenesis must therefore be indirect in all cases, chance alone determining 
whether the new ecologism is of advantage or not. DETTO, who agrees with 
Kiegs at so many points, holds in direct opposition to him that the external 
world causes no changes whatever in plants; every plant character is an organiza- 
tion character (in Niigeli’s sense) and the external conditions in which a plant is 
placed act merely as releasing stimuli. 
x k should be read carefully by all who are interested in the philosophy 
of adaptation, since the volume as a whole is so written as to stimulate 
thinking. However, it seems to the reviewer that the perspective is frequently 
distorted. In this country, at least, there is no need for such a continuous and 
hearty lampooning of teleological and vitalistic views, for they have been long 
since abandoned by most scientific investigators. That chance determines suc- 
cess and not a prudent foresight on the part of the plant is certainly the common 
view. Again, if one holds to a potentielle Variationsbreile wide enough to embrace 
all changes that ever occur in plants, it is obviously impossible ever to demonstrate 
the contrary by experiment; it is a concept incapable of proof or disproof. It 
seems far better to hold that both the organism and the environment are nee 
to secure the evolution of new forms; any other view seems to the reviewer funda- 
mentally unthinkable—HEenry C. Cowles. 
Matthias Jacob Schleiden. 
AN APPRECIATIVE biography of SCHLEIDEN by M. Most 
on the centennial of his birth, April 5, 1904.2, MOsrus was re hi 
to SCHLEIDEN (whose second wife was Mosrus’s maternal aunt), and to fal 
family sources of information have been open. SCHLEIDEN’S life was papi a of 
save for two incidents; the one an attempt at suicide on account of eh tion 
success and dissatisfaction in the legal profession, and the second his resignal 
of the professorate at Jena because of the refutation of his theories on oe ape 
of cells and the formation of the embryo. Clear and vigorous in ceo to 
expression, he demanded accuracy and lucidity in others and was ever If 
US, was published 
lated by marriage 
iv 
-? MOstus, M., Matthias Jacob Schleiden zu seinem 100 Geburtstage- vo. PP: 
+106, portrait, figs. 2. Leipzig: Wilhelm Engelmann. 1904- M2.50 
