224 



THE TEACHING BOTANIST 



the cortex and pith in Corn, which are not separable, and 

 colors must merge one into the other. Most important is 

 the practice of recognizing the different tissues with naked 

 eye or hand lens ; much histology without a microscope, is 

 possible, and important in many features of adaptation. 



It will be profitable to examine cross-sections of other 

 young twigs and different kinds of wood. 



Experiment No. 8.- -For this, some form of auxanometer or 

 growth-measurer, is needed, of which there is a great variety 



of forms. Only a self-recording 

 form is really useful, and those 

 on the market are very expen- 

 sive. A fairly satisfactory form 

 can, however, be made as fol- 

 lows, at a cost of about $2 (see 

 Fig. 22). Buy a dollar clock, four 

 inches in diameter, and remove 

 hands, face, and surplus wheels 

 until only the steel spindle, three- 

 quarters of an inch long, stands 

 up above the works. Have turned 

 on a lathe a cylinder of hard 

 wood one foot long and an inch 

 in diameter, in one end of which 

 a hole somewhat more slender 

 than the spindle of the clock is 

 turned, truly centred. The cyl- 

 inder may now be forced gently 

 down on the spindle, on which 

 it will revolve evenly once an 



hour. Have turned also from good maple a double wheel 

 like that shown in the figure ; the outer wheel is grooved, 



FlG. 22. A recording auxa- 

 nometer. X . 



