94 



by a velvet collar. A Ijlack eanllioard collar. Fig. III. I5C, slips over the 

 bottle and rests upon the platform below the bottle. A piece of white card- 

 board on the platform serves as a reflector for the light entering the bottle. 

 It is this dnll red light which is carried to the olijective of the microscope 

 and used to make the readings. Tliis light enters only when making the 

 readings and has not, in the number of cases tried, produced any stinuilus 

 that would effect the experiment and alter the response to the norma 1 light 

 stimulus. However, I have yet to try experiments on I'halaris. 



The internal construction of the box, Fig. II, consists merely of a ver- 

 tical rod on which works a burette clamp. The rod is so placed that a test 

 tube containing the plant under study can be adjusted easily into pcsition 

 opposite both the iris and the objectiA e of the microscope. The door of the 

 box is fitted with strips of velvet so as to make it light proof. 



To use the apparatus, sccdluigs are grown in soil, sawdust, etc.. in test 

 tubes in the dai-k i-oom. These culture tul)es should always be held in a 

 \ertical position while being adjusted in the box for study. Tlie box is 

 •io:i(l('d" ill the dai'k room .nid the plants jihiced so as to be in the held of 

 the microscope. The iris is closed and the door of the box is locked. 

 The plant is then brought into focus using the illumination secured by rais- 

 ing thi> collar. \'A'. to .-i suHicicnt height and thus iicrmittiiig the i-etiecttni 

 light to enter the bottle from bclow. Readings are taken at intei'vals of 

 several minutes befon^ o]ieniiig the iris in order to l)e certain that no geo- 

 tropic slimnli other than the normal arc acting. When no readings ;ire 

 being taken the colhir rests upon the platform. 



The plant is then latei'ally stinndateci by openiim the iris to any de- 

 sired size for a delinite length of lime. 'IMie mirror relleets th(> light 

 tlirough the iris onto tiie plant. 



The microscope is kept covered at all times with a pliot.ographei'"s focus- 

 ing cloth. All of the readings are made under this cloth. 'I'his prevents 

 any light from passing through the microscope and l)eing fo<-used onto the 

 plant. 



To record the results a graphic record may be made, using the ordi- 

 nates to denote the extent of cnrvatui'e in spaces on the micrometer e.ye- 

 piece, and tlie abscissas to denote the time of stimulation, or i)resentation 

 period, the latent i)eriod. and the length of time for the comjtletion of the 

 response. Figure I \' illustrates such a record: 



