MOVEMENTS OP PROTOPLASM. 19 



For the first studj-, the examination of protoplasm, a micro- 

 scope magnifying from two hundred to six hundred diameter?, 

 will be required, together with a small outfit of slides and covers ; 

 and for the examination of growth a zinc box constructed as 

 directed in "The Dependence of Growth upon Heat." 



I. The Behavior of Protoplasm in a Living Vegetable Cell. 



For all necessary details as to the chemical reactions of proto- 

 plasm, see 124 and the exercise on page 8 of this "Praxis." 

 At present it is proposed to call attention to the various 



Movements of Protoplasm. 



(a) Material. The delicate hairs from the young leaves of 

 almost any pubescent plant will serve for the demonstration 

 of these movements, but the following are recommended on 

 account of their abundance and excellence : stamen-hairs of 

 Spiderwort (Tradescantia), hairs from the 3"oung leaves of 

 squash and nettle, and from the velvet}- leaves of many culti- 

 vated exotics. 



(5) Preparation of specimens. Remove b}- needles, forceps, 

 or scalpel a very little of the epidermis witii its attached hairs, 

 and place it at once in a little water on a glass slide. In placing 

 the thin glass cover on the specimen be careful to exclude all air- 

 bubbles and not to crush the (jells. If necessary, put a fragment 

 of glass under one edge of the cover, to lighten the pressure on 

 the object. If the hairs are suitable for the examination, the 

 delicate threads of protoplasm ought to be distinctly seen through 

 the cell-walls, and, after a little time, a movement of translucent 

 granules should be seen in them. If, after a few moments, no 

 movement can be detected, warm the slide a little with the hand 

 and again observe. If no movement should now be seen, add 

 to the water on the slide a little dilute glycerin ; this causes 

 slight contraction of the protoplasmic lining of the cell, and 

 probablj' the movement can then be observed in the threads. If 

 not, do not waste time over the specimen, but try a fresh one. A 

 power of 200 diameters will answer for this work, but one of 500 

 is better. 



(c) Questions to be answered hy the specimen. If the student 

 has secured a good preparation, in which the movement of gran- 

 nies in the threads can be .seen distinctly, he can easily answer 

 the following queries : What is the rate of motion of the gran- 

 nies at the temperature of the room? Do the threads remain 



