THE METHOD OF MOVEMENT 157 



Although adequate quantitative data are not available 

 for showing the influence of turgor of leaves on transport 

 from them, it is obvious that turgid tissues may receive 

 solutes from relatively flaccid tissues. The development 

 of turgid sprouts on potato tubers in a dark cellar, when 

 the supplying tuber is distinctly flaccid, is a case in point. 

 Other examples of movement from flaccid to turgid tissues 

 have been frequently observed in the emptying of other 

 storage organs such as fleshy storage roots of beets, carrots, 

 turnips, etc., the scales of an onion or other bulb and the 

 cotyledons or endosperms of sprouting seedlings. In all 

 the experiments reported in Table 19 the storage tissues 

 appeared distinctly less turgid than the receiving tissues. 



Miinch, foreseeing the possible objection that turgor in 

 the leaf may be reduced by transpiration, offers the expla- 

 nation that, when the turgor of the leaves is reduced, the 

 turgor throughout the entire plant is correspondingly 

 reduced; for the entire water system would be put under 

 tension so that the decreased pressure in the leaves would 

 be counterbalanced by a corresponding increase in tension 

 on the water passing out of the receiving cell. (This would 

 be cell B in Fig. 9 and cell C or cambium in Fig. 10.) 

 Although, in a simple system where the resistance to 

 movement is slight and the walls are rigid, there might 

 be such a rapid transmission of tension, I am not convinced 

 that in a large plant this would be possible. Although 

 a transmission of tension through the water-conducting 

 system would meet much less resistance than through 

 any other tissues and might therefore put the receiving 

 cell, such as C in the diagram, under tension, a failure to 

 transmit such a tension from the receiving cell or cambium 

 backward through the sieve tubes, along the entire path through 

 which the sugar is moving from the flaccid leaf, would offset 

 any advantage resulting from withdrawing water from the 

 receiving cell, and reducing its turgor. The walls of the 

 phloem cells, furthermore, seem not to form a rigid tubular 

 system, as in the xylem, and it seems unlikely that they 

 would allow for transmission of such tensions. Without 



