SUMMARY 223 



The results described lead to the following generalisation : 



1. Thermonastic movement occurs in organs which, 

 under variation of temperature, exhibit unequal growth of 

 their two sides. 



2. When the inner or upper side is the more active, rise 

 of temperature induces a positive thermonastic movement, 

 that is, the opening of the flower. 



3. When the outer or lower side is the more active, rise 

 of temperature induces negative thermonastic movement, 

 shown by the closure of the flower. 



The following tabular statement describes the different 



types of thermonastic organs : 



Table XIX. — Showing the Effect of Rise of Temperature 



ON Thermonastic Movement. 



Type of reaction Specimen 



/■ Zephyranthes 



„ .^. , , . 1 Crocus 



Positive ; movement of openmg -, European Nymphaea 



i ( Indian blue variety of Nymphaea 

 Kegathe ; movement of closure I Indian White Water-Lily 



Summary 



Thermonastic movements are induced in growing 

 anisotropic organs, the two sides of w^hich exhibit different 

 rates of growth under variation of temperature. 



Rise of temperature induces greater enhancement of the 

 rate of growth of the more active side ; fall of temperature 

 gives rise to the opposite effect. 



Two types of thermonastic movements are met with, 

 the positive exhibiting a movement of opening during rise 

 of temperature ; in these the inner side of the organ is 

 relatively the more active. Examples of these are seen in 

 Crocus, Zephyranthes, and in European and certain Indian 

 Nymphaeas. 



In the negative type, rise of temperature induces a move- 

 ment of closure. Here the outer side of the organ is the more 

 active. The Indian White Water-Lily belongs to this type. 



