No. 633] SHORTER ARTICLES AND DISCUSSION 3G5 



S.A. 



of roots in other regions of a plant of Bnjophylhim and of even 

 stopping the further growth of roots which had started to grow. 



(2) In a whole plant, because of a cer- 

 tain morphological structure, the nutrient 

 channels are such as to carry food mate- 

 rial to growing regions. A plant grows 

 at both ends and so long as these are in- 

 tact and growing food Hows toward them. 

 If removed, food Hows to other points 

 and starts the growth of dormant short 

 buds or root primordia. Once a stem 

 or root has started growing Loeb's 8 ex- 

 periments show very clearly that the 

 mass of growth formed is proportional 

 to the mass of materials available. 



I believe that light is thrown on this 

 problem by some experiments which I 

 performed in 1910, while a student at 

 Columbia University, and repeated at 

 Princeton in 1912, but which have never 

 been published. They are designed to 

 divide a plant into two parts physiolog- 

 ically but not morphologically. A jet 

 of steam was directed against the stem 

 of a young bean plant between cotyle- 

 dons and first pair of leaves in order to 

 kill the tissue throughout the stem in 

 this region. In some plants the leaves 

 and growing tip above this region wilt 

 and die but in many cases not only does 



why tilt's. 

 Loeb, J., J oi 



