TEANSLOCATION OF NUTEITIVE MATEKIALS 225 



be forgotten, however, that all cell-membranes are per- 

 forated by very delicate strands of protoplasm which extend 

 from one protoplast to another. There is here a path of- 

 transport by which the protoplasm can pass substances from 

 cell to cell as already suggested. 



We may find proofs that the pathway lies along the bast 

 by experiment carried out on plants in which translocation 

 is actively proceeding. If we cut a branch from a suitable 

 vigorously growing tree and remove from near its free end 

 a ring of tissue extending inwards through the bark and 

 cortex to the cambium, and then place all the lower part in 

 water or moist earth, very marked effects follow. After 

 some time, perhaps a few weeks, adventitious roots will be 

 put out from near its end. Those which arise below the 

 missing ring will be few and of small size ; those from above 

 this region will be numerous and strong, and will continue 

 to elongate. Any buds that may be on the part below the 

 ring will not develop, while those above it will grow normally 

 or even more freely than on an uninjured branch. The 

 tissue immediately above the ring will become somewhat 

 hypertrophied and show a decided swelling. 



The continuance of the growth shows that the water 

 supply has not been cut off, but the different behaviour of 

 the parts above and below the excised tissue tells us that 

 the supply of nutritive material to the latter region has 

 been interfered with, and the buds and adventitious roots 

 it bears gradually perish of inanition. The passage of 

 any food or nutritive material across the ring has become 

 impossible. 



If a similar incision is made into another branch, but is 

 not carried so far inwards if, that is, the ring of tissue 

 removed consists only of the structures external to the 

 bast these appearances do not accompany or follow the 

 wound. Evidently in this case the translocation path has 

 not been interfered with. We may safely conclude there- 

 fore that the transport of elaborated products, chiefly food, 

 is the principal function of the bast. 



15 



