2386 



Journal of Applied Microscopy 



Methods in Plant Physiology. 

 XII. 



HELIOTROPISM— Continued. 



5. Localization of tlie Sensitive Area. — Tliis experiment is designed to answer 

 the question, Are the organs of the reception of the stimulus and the organs of 

 response the same tissue ? Raise in the dark chamber seedlings of German 

 millet {Setaria Italicd) in a crock filled with earth level with the rim. While 

 germinating, this culture must be attended every day to insure having the proper 

 supply of moisture present. When the plants have reached a height of 1 cm. 

 above the earth, caps of tin-foil are to be slipped over three or four of them. 

 These caps are made by rolling pieces of tin foil 5 mm. by 10 mm. around a pin 

 whose head has been cut off. Thus a cylinder 10 mm. long is made. One end 

 of the cylinder is to be flattened and turned at right angles before removing it 



Fig. 1.3. — A damp chamber in use on a klinostat. The power is fur- 

 nished by a small electric motor. The speed is reduced by the 

 intervention of a worm-gear. 



from the pin, the flattened part being about 3 mm. in length. The caps should 

 be handled by means of small forceps only. At the expiration of 6 to 12 hours 

 the contrast between the capped seedlings, which remain upright, and the others, 

 which are bent strongly towards the light, is very marked. Proving that the 

 sensor and motor organs are in different tissue. 



6, Growth of Stems and Roots when Light is Excluded and Gravitation is Neutral- 

 ized. — Employ seedlings of corn {Zea Mais) 4 to 6 cm. long and fasten them to 

 supports in a damp chamber as shown in Fig. 17. The damp chamber should 

 be immediately started revolving on a klinostat in a dark room. Some of the 

 seedlings should be placed parallel and others at right angles to the axis of revo- 



