CH. II] ETIOLATION. 49 



when a student at Wilrzburg, restored a healthy green to 

 a chlorotic branch of Robinia by screwing a funnel into 

 the tree close to the base of the branch, and pouring into 

 it a solution of an iron salt^. 



In the absence of chance material, chlorotic plants 

 must be produced by growing them, by the water culture 

 method, without iron. It is probably best to grow some 5 

 or 6 iron-starved plants so as to have control plants and 

 to make sure of material for several experiments. Add 

 a few drops of iron chloride solution to one culture jar, 

 and use another for Gris''' experiment, which consists in 

 painting a leaf with very dilute ferric chloride solution. 



(72) Form of etiolated plants. 



For a thorough study of the changes of form and 

 structure which accompany etiolation it would be neces- 

 saiy to grow a great variety of plants. The best for the 

 purpose are plants produced from tubers or bulbs, or from 

 large seeds full of reserve material, since here the effects 

 of darkness in producing starvation do not complicate the 

 result. Among Dicotyledons Dahlia, Helianthus tuberosus, 

 Hop, and Beans (Faba and Phaseolus) may be grown. 

 Among Monocotyledons any of the cereals and Narcissus. 



In each case control plants of the same species must 

 be grown in light. Compare the two sets as to develop- 



1 I cannot be sure of the details, but I remember the fact. [F. D.] 

 ' For an account of the experiments of Gris see Sachs, Physiologic 



VegitaU (French Trans.), p. 159. Also Sachs, Arbeiten, iii. p. 433, for 



Chlorosis. 



n. A. 4 



