1892.] Two Schools of Plant Physiology. 215 



and Chemistry to the results of action connected with the 

 living portions of the plant. The difficulty lies not only in 

 the extreme delicacy of the material in i[iiestion but in the 

 danger of interference with the processes as they go on. 



Schwendener and his followers claim that we have not yet 

 reached that point in the development of the science where 

 such questions may be asked with a reasonable hope of a 

 satisfactory reply. Our knowledge is too meagre and our 

 means of acquiring more are as yet inadequate. In other 

 words, they claim that the methods now used are incorrect, 

 inasmuch as they do not aim at constructing a theory which 

 shall satisfactorily account for certain facts, 1 nit they presup- 

 pose the existence of the facts, and the methods result, for the 

 most part, in mere conjecture- ami speculations which count 



Whether this view be true or false it is unquestionably the 

 source of the implication of narrowness and onesidedness 

 before referred to, as obtaining against Schwendener among 

 his own cotemporaries and his own country. Even here, 

 however, it cannot be said that there is any actual difference 

 in opinion between the two schools, only that the methods and 

 results so far obtained by the one, are held in very light 

 esteem by the other. It is very different when we come to the 

 various problems connected with the growth and motion of 

 plants. It is in this field particularly that the difference of 

 opinion between the two men leads to positive diiference in 

 the teaching and modes of treatment of several important 

 questions. 



Schwendener gives, each year, a course of advanced lectures 

 covering the following ten subjects. 



1st, The mechanical principle in the development structure. 



2nd. Theory of leaf position. 



3rd. Mechanics of stomata. 



4th. Bending of the medullary rays in eccentric secondary 

 growth in thickness. 



5th. Torsion, as caused by hygroscopical changes. 



6th. Ascent of sap ; hydro-mechanics of. 



7th. Mechanics of twining. 



