28 STUDIES IN PHYSIOLOGY. 



XIV. Wateii-Cultuue. 



In the study of water-culture no plants can be more easily 

 managed than buckwheat and Indian corn. Secure good seed- 

 lings, and treat them as described in G6'J. After the plants 

 have become well established in their new surroundings, use for 

 the nutrient liquid the following solutions in a fixed order, and 

 with the precautions laid down on page 249. 



XV". Assimilation Phopee. 



Chlorophyll and other coloring-matters. Make a solution of 

 the pigment hy placing bruised leaves of grass in strong alcohol 

 for a few hours, and keeping them from the light. It is well to 

 prepare at least ten ounces of the strong extract, which can be 

 used in all the following experiments. 



Examine the color of about an ounce of the above extract held 

 in a small vial. What is its color by transmitted and by re- 

 flected light? In the latter examination it is better to throw a 

 strong light from a burning-glass or double convex lens upon the 

 surface of the liquid. How long will the liquid keep its color in 

 the strong light? 



Treat, as directed in 774, one ounce of the extract which has 

 not been exposed to light, and place the turbid mixture aside in 

 a dark place until it becomes clear. What are the colors of the 

 upper and the lower layer into which it separates ? 



If a microspectroscope is available, make on paper projections 

 of the spectra of the following substances: (1) Chlorophyll solu- 

 tion, (2) the upper layer of the liquid just mentioned, and (3) 

 the lower layer of the Lc^uid. Examine also the spectrum of a 

 thin green leaf. 



If possible, examine the colors of autumnal leaves, and of 

 alcoholic extracts from colored flowers and colored fruits. 



