THE METHOD OF MOVEMENT 



179 



Table 20. — Areas of Measured Potato Stolon 



{From Crafts) 



Stolon av 



External phloem . 

 Internal phloem . 

 Total phloem . . . . 



Sieve tubes 



Sieve pores 



Walls of phloem . 



Cortex 



Xylem 



Pith 



Sq. mm. 



9.5 



1.15 



0.61 



1.76 



0.40 



0.009 



0.57 



% of stolon 



18.5 



5.7 



0.13 



6.0 



^36.5 



•=39.5 



*5.5 



* Estimated from unpublished data. 



approximately 9 cc. of a 10 per cent solution. This would 

 have to move at a linear rate of 19 cm. an hour if the 

 total cross-sectional area of the entire phloem, walls and 



.,11 t. , / 0-89 X 9 \ ,„ 



lumen, were available as a channel I n ni-r y 24 / ^ ' 



or 83.0 cm. per hour if the flow were restricted to the 

 sieve tubes. He estimated the total cross-sectional area 

 of the sieve strands (pores) to be 2.3 per cent of that of 

 the sieve tube. Through the sieve pores, therefore, the 

 rate would have to be 3,609 cm. per hour. On the basis 

 that 0.89 g. of dry matter was moving in the pure state, 

 in which condition it would occupy approximately 0.6 cc, 

 he estimated it would have to move at a hnear rate of 

 1.42 cm. per hour if the entire cross-sectional area of the 

 phloem were the channel. He points out that probably 

 not more than 10 per cent of the phloem area could be 

 occupied by streaming protoplasm and only half of this 

 could be moving in one direction, so, on the assumption 

 that protoplasm is carrying sugar in the pure state equal 

 to its own volume, it would have to move at a linear rate 

 of 56.8 cm. per hour, or 9.47 mm. per minute. The maxi- 

 mum rate of streaming he observed in stolon parenchyma 

 was only 1.8 cm. per hour (0.3 mm. per minute), and since 

 the above figure takes no account of the still greater 



