226 THE TEACHING BOTANIST 







ing windows open at night, etc. In case there is not room 

 under the wheels for both clock and plant, the latter must be 

 placed to one side, and the thread run over some smooth 

 support, such as a clean screw-eye, as shown in the figure. 



Another physiological topic of much importance that may 

 well be taken up here is that of the autonomous movements, 

 particularly circumnutation, of stems. This subject is easy of 

 experiment, and particularly good directions are given by 

 Darwin and Acton in their " Practical Physiology." The glass 

 plate on which records are to be taken may be placed at any 

 desired height by supporting it upon three legs in which 

 grooves to hold the plate are sawn at different heights ; the 

 legs are held to the plate by a wire bound around them all. 

 Particularly instructive in this study are the hypocotyls of 

 seeds just bursting from the ground. The well-nigh universal 

 occurrence of circumnutation movements is a point of con- 

 siderable value as knowledge. 



XIII. The Cellular Anatomy of the Root 



48. What " is the cellular anatomy of a typical root ? 

 Answer from a study of the specimen supplied. 



49. What is the external structure of the young roots 



of the Radish ? 

 In particular, what is the structure, distribution, 



and mode of connection of the root hairs with 



the root ? 

 How much of the internal structure of the tip can 



you see with your lenses ? (Something more 



will be shown if you soak the tip for a few 



