Vol. 6 No. I 



TORREYA 



LIBRARY 



January, 1906 NEW YORK 



BOTANICAL 



POLARITY IN THE WEEPING WILLOW ^''''• 



By E. a. Andrews 



The experiments of Vochting showed marked polarity in the 

 new growths from cut-off twigs of the osier willow when very- 

 young, but in older twigs and in some other species of willow 

 less marked polarity. The following observations upon the 

 older twigs of the weeping willow i^Salix babyloiicd) show new 

 growth of pieces without observed polarity. Being manifestly 

 incomplete, they are published chiefly as suggestive of problems 

 to be solved. 



In October before the leaves had fallen, twigs 10-15 mm. 

 thick and 30 cm. long were cut from a young weeping willow 

 about ten feet high. The branches used were erect and not the 

 pendent twigs. When these were put with one half in the water 

 and the other in the air (not especially moist) they eventually 

 formed roots in the water and leaf-buds in the air, whether the 

 twigs were inverted or not. During the winter the leaf-buds 

 elongated as branches 1 5 cm. long. The only leaves formed 

 under water were from visible buds while in the air there were 

 leaves formed in addition to those coming from visible buds. It 

 was thought that the roots came out sooner from the basal ends 

 in water than from the apical ends in water, but this may have 

 been due to differences in temperature caused by one set of jars 

 being nearer to the source of heat. Transplanted into earth, 

 some lived several months, but both the inverted and the non- 

 inverted twigs died. 



In March and April, when the leaves were first showing green 

 but had not yet expanded, twigs of the same small tree showed 

 a marked ability to form roots from any part in water and leaves 

 from any part in air, without difference between basal and apical 



[No. 12, Vol. 5, of TORREYA, comprising pages 207-233, was issued January 

 10, 1906.] 



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