102 
date. This book was revised in 1868 with no change in the 
definitions (?) In 1887 the “Lessons in Botany” were printed in 
which the definitions of the various branches of the subject cor- 
respond much more nearly to the present condition of the science. 
Even here there is a striking lack of definiteness and precision as 
compared with the definitions of the other later authors. For ex- 
ample, he says: “The study of the actions of plants, or of their 
parts, of the ways in which a plant lives, grows, and acts, is the 
province of physiological botany or vegetable physiology.” 
Notice here the use of the two terms as identical. Pfeffer defines 
plant physiology as follows: ‘Physiology has the task, to find out 
exactly, according to measure and number, the processes which 
take place in an organism, to trace back these processes to their 
origin, and to learn their signification in the economy of the organ- 
ism.” The most restricted text book definition of the word physi- 
ology is probably that of Wiesner’s, who says: “The province of 
physiology, using the term in its restricted sense, is to trace back 
all the phenomena of life to mechanical processes.” Nothing — 
could be more true and at the same time comprehensible than this. 
The only objection to it is, it is too restricted to cover what even 
Wiesner himself includes in his text book under the head of 
physiology in its restricted sense. 
With the exception of this peculiar view of the province of 
physiology, Wiesner’s definitions of the branches of the science 
very fairly represent the present accepted use of terms and man- 
ner of treatment. His exposition of the subject is briefly as fol- 
lows: There are two branches which include the entire field of 
scientific botany, morphology and physiology. The first concerns 
itself entirely with the form relations of plants and their ports, the 
second with the conditions and phenomena of the life of the plant. 
Morphology is subdivided in four branches. 1. Descriptive mor- 
phology, or description of the outer form of organs; 2. The inner 
structure, or anatomy; 3. Development history, or tracing the de- 
velopment of plant, or organ; 4. Systematic morphology, or trac- — 
ing the organs back to a few types. 
Physiology is subdivided in two brances: 1. Physiology in its 
restricted sense as defined above; 2. Biology, or the consideration 
of vital processes, which cannot, at our present stage of knowledge 
be traced to any mechanical causes. 
