234 Philosophy of Botany. 



mention in the line of physiological researches the discoveries 

 of Jioliuniel Nomec and G. Haberlandt in respect to geotro- 

 pism — that is, the faculty of directing the growth of the roots 

 in the direction of the earth's axis. 



This phenomenon had always been accepted as a simple fact 

 of nature, without any inquiry into the directing cause of this 

 movement. 



Physiologists had some time ago established the nature of 

 the function of the delicate hairs and the otoliths in the semi- 

 circular canals and ampulla^ of the vertebrates, including man. 

 to be organs of equilibration and localization ; they had also 

 found that the so-called auditory cells on the extremities of 

 insects and of Crustacea, which are of a similar structure, sub- 

 serve the same purpose. It is the act of pressure by gravity 

 of these otoliths, now called statoliths, upon those fine hairs, 

 which excites the living protoplasm in these cells to effect 

 functions, resulting in motions by which animals become 

 sensitive of disturbances in their normal position in relation 

 to normal or desired direction of their bodies, in relation to 

 gravity, and try to correct them. By a chain of observations 

 have the above observers determined that an analogous appa- 

 ratus also subserves the geotropical and heliotropical move- 

 ments of plants. 



Specialized amylaceous granules in the tips of the roots, 

 suspended in the protoplasm, and obeying the call of gravity^ 

 secure the centripetal movement. Likewise is it a statolithic 

 pressure in the internodes of the grassculum, which causes a 

 swelling on one side of such a blade, and thereby a flexion or 

 erection of the culm, when, for instance, the culm of wheat or 

 stalk of corn had been prostrated by wind or rain. 



Thus we have a very interesting elucidation of correlation 

 of physical phenomena between plant and animal in the or- 

 ganic world. 



It has been my intention to give a short review of the prob- 

 lems toward which botanists have been aiming, and at which 

 they have, notwithstanding the changing demands of suc- 

 cessive periods, sedulously working, closer and closer ap- 

 proached, ever since the time when twenty-two centuries ago 



