MISCELLANEOUS 

 Table 48. Changes in Amounts of Substances in Mother-Tubers 



423 



from the mother-tuber are of importance in promoting the growth of the 

 daughter plant and that the mother-tuber must be of a certain mmimum 

 size in order to furnish enough of these substances. Denny's work does not 

 disprove this claim. It is also claimed that the mother-tuber serves as a 

 water-storage organ. Denny observes wilting in some cases after mother- 

 tuber removal, but in the later stages of growth this did not reduce the jdeld. 

 His plants were gro^vn with adequate water. Water storage may have some 

 significance in dry seasons. 



Flower Color of Hydrangea macrophylla 



The amount of aluminimi available determines the color of the flowers 

 of the common hydrangea, Hydrangea macrophylla DC. 



Many gardeners and a number of scientists have debated the question, 

 WTiy are the flowers of our common hydrangea (H. macrophijlla) some- 

 times pink and at other times blue, and how is it that some flowers on cer- 

 tain plants the same year are pink while others are blue? 



Allen ^ gives a critical review of the investigations on this question and 

 describes a set of experiments that appear to give the answer. He states 

 that several explanations have been offered, but that recently the question 

 has resolved itself into whether it is an abundant supply of aluminum or 

 iron in the flower that makes it blue, a medium supply that produces a 

 mauve flower, and low supply that gives a pink flower. His answer is in 

 favor of aluminum salts. 



Part of his evidence is given in Fig. 171. In the upper left corner is a 



