THE PRINCIPLES OF BOTANY. 
169 
contraction is observed to occur in the reticulated ducts as they 
approach the surface of the root, and before they come into 
connection with the surrounding wood they become reduced to 
half their original width.* 
That our plant is truly parasitic is now shown beyond a 
Fig. 1 . —Mistletoe on Robinia pseudoacacia. a. The parasite cut off 
below to show the wedge-like insertion of its wood into the foster¬ 
parent (c). b. The radicle of mistletoe inserted into the wood. 
d. The central pith. These radicles are light green. 
Fig. 2.—Branch of Robinia with a portion of the bark removed showing 
the mode of growth of the radicles. 
doubt; that it is also exogenous is seen from sections of both 
young and old mistletoe stems; but though this is so, we view 
* ‘Transactions of the Linnsean Society,’ vol. xxiv, pp. 175-6. 
