TRANSLOCATION OF CARBOHYDRATES 463 



that the operation did not prevent the removal of the carbo- 

 hydrates ; the two halves of the leaf apparently lost their starch 

 equally quickly, 



Czapek maintained that since the elements of the vascular 

 bundles alone were completely interrupted by the transverse 

 cuts, while the parenchymatous elements were still in connection 

 laterally and diffusion could proceed in the latter equally well 

 in all directions, translocation of the sugars must go on in the 

 sieve-tubes. 



Where cross-connecting sieve-tubes did not occur, the in- 

 cision produced a complete interruption of the paths of trans- 

 location, whilst this was not so where such cross-connections 

 were present. In the latter case the sugars could still pass into 

 the sieve-tubes of the uncut portion of the petiole and travel 

 through them. 



However Haberlandt refuses to accept Czapek's assumption 

 that in parenchymatous tissues horizontal and longitudinal 

 conduction can proceed with equal ease. In fact he considers 

 that the results of Czapek's incision experiments are " an 

 interesting confirmation " of his own theory that the protoplasm 

 of the transverse walls of parenchymatous cells is much more 

 permeable than that of the lateral walls, and that elongation 

 of cells indicates the direction in which the cell contents most 

 readily travel. 



Haberlandt himself attaches greater importance to some of 

 the experiments made by Schimper in 1885. In one of these 

 the veins were carefully removed from a leaf of Plantago 

 media — an operation which can be performed without injuring 

 the surrounding nerve parenchyma to any extent, since the 

 bundles are provided with a sheath of thick-walled, unlignified 

 cells which easily break away from the starch sheath. Plants 

 with leaves treated in this way, together with normal control 

 plants, were placed in darkness from May 31 to June 10. At 

 the end of this period Schimper examined the starch and 

 sugar content of the leaves and concluded that the operation 

 did not markedly hinder the emptying, and that the vascular 

 bundles were unnecessary for the normal translocation of the 

 carbohydrates. 



However the details given are insufficient to enable one to 

 rely upon the experiment as being critical for determining 

 the question at issue. The sugar content is the most im- 



