1897] CURRENT LITERATURE 295 
The text of a recent popular address by Dr. Noll is of interest in this con- 
nection.*, The popular superstitions and fanciful theories of the intelli- 
gence, spiritual life and sensibility of plants since the time of Empedocles 
(fifth century B. C.) are brought into review in the light of modern investiga- 
tion, and following a summary of the results upon which the current theories 
of irritability are based, the author enters upon a highly metaphorical discus- 
sion of the true nature of the sensibility of plants. Defining a sense he says: 
“The ability to feel the relations of the surrounding world, or objectively 
expressed, to receive these relations as stimuli, and react by variations in the 
life processes, is to be designated as sense.” Psychologists are not so easily 
satisfied, however. With such definition as a basis the author proceeds to 
the statement, “that portions of plants are to be recognized, which not only 
can, but must be designated as sense organs.” To term the pulvinus of 
Mimosa a specific sense-organ does not attain the advantage of inclusion of 
similar things under single terms as claimed by the author. 
It is to be seen that the greater portion of the paper was not meant to be 
taken too seriously or literally by the audience to whom it was addressed, for 
in the concluding paragraphs it is pointed out that the presence of conscious- 
ness or of any of the psychic functions of a centrally organized nervous sys- 
tem has not been demonstrated in plants, and therefore that real senses are 
wanting, since a reflex connection of the motor and sensory zone meets every 
necessity of existence. Weber's law of the relation of stimulus to reaction, 
once thought to be a test of the presence of consciousness, has been found to 
apply to some reactions of plants, but since it is possible to construct a 
machine which will obey this law, it has lost its significance in this connec- 
tion. 
The author has appended a series of critical notes on the various questions 
Suggested in the lecture. An interesting comparison is made of the greater 
degree of perfection of the sensibility to gravity in the plant, with the func- 
tion of the otocyst in lower, and the semi-circular canals of the ear in higher 
‘animals. Great importance is attributed to the interprotoplastic threads in 
the conduction of impulses, though the writer does not seem aware of the 
fact that the interruptedness of the nervous tissue of animals is universally ; 
accepted. In harmony with the work of the reviewer the curvature of ten- 
_ drils in response to changes in temperature are not Shik ae as reactions in 
the same sense as those to contact, etc. 
__ Adiscussion is given of Czapek's objections to Noll’s theory of the irnta- 
_ bility of secondary roots, and of Pfeffer’s adverse criticisms of certain phases 
of “heterogene Induktion,” but no new facts are adduced. The value of fig- — 
ae urative discussions of the nature of the irritability of plants is. extremely 
Soutttal. In no part of aneneneee sel BE CERES HER ; 
*Das Sinnesleben der Pflanze. ‘ . Ber. u. d. Ser : 
Natur Ges i, disc ming aeee 1896. 
