IRRITABLE RESPONSE 



225 



and finally the screw connecting the spindle-arm and works, are tightened, 

 and the experiment may begin. Care must be taken never to allow the 

 weight of the plant to be unsupported, else the spindle-rod may be greatly 

 bent and damaged. Further the adjustable support must be neither too 

 high nor too low, else the spindle-rod may "bind" and refuse to tum. It 

 is very rarely, if ever, in educational work that any position other than hori- 

 zontal or vertical is needed, but if desired it may be attained as in figure 63, 

 the adjustment being so made that one of the legs of the instrument rests 

 firmly on the support or table. This position brings much more strain 

 upon the works than either of the others, and consequently should be em- 

 ployed as rarely, and with as light weights, as possible. In using the instru- 

 ment the following precautions should be ob- 

 served. No water should be allowed under any 

 circumstances to get into the works, and the in- 

 strument should be exposed to as little moisture 



Fig. 63. — Demonstration Kltnostat arranged for use at an angle; X h 



as possible. It should also be kept constantly closed from the dust. Sudden 

 or extreme strains on the works must be avoided. Like all clockwork it 

 must be cleaned and oiled at intervals, the length of which depends upon the 

 amount of use. 



A form superficially resembling the instrument just described is sup- 

 plied by the Cambridge Botanical Supply Company, and another, of some- 

 what similar construction, is offered by the Stoelting Company. Yet another, 

 driven by a spring clock, but having a new form of support (a right-angled 

 frame carrying both clock and the revolving object), is offered by the Cam- 

 bridge (England) Scientific Instrument Company. Klinostats giving an 

 intermittent revolution, needed for some special purposes, have been described 

 by F. Darwin (Annals of Botany, 6, 1892, 245), by Pfeffer (Jahr- 

 biicher fur wissenschaftliche Botanik, 35, 1900, 738), and by Fitting (Pfef- 

 fer. "Physiology," 3, i°9)- 



