THE METHOD OF MOVEMENT 139 



resulting from cutting, it could not completely obviate 

 abnormal pressure changes. It is also interesting that 

 in the same drawing he has indicated by arrows the stream- 

 ing of protoplasm in the companion cells, and these cells 

 do not appear collapsed or plasmolyzed. 



Though Lecomte considered this squeezing of albuminous 

 globules through the sieve pores as an indication of normal 

 movement, he clearly recognized that cutting may cause 

 an abnormal flow for considerable distances. For example, 

 he discusses the work of Fischer (1885) who demonstrated 

 that the appearance of the slime plug on one side of the 

 sieve plate was an artifact due to cutting or other injury, 

 and he states that such an efTect of cutting may be evident 

 at a distance of 2 to 12 cm. in the petiole of Cucurbita. 

 Whether Lecomte's observations and drawings represent 

 a real and normal unidirectional flow of sieve-tube contents 

 or whether the apparent flow resulted from the method 

 of treatment, cannot be settled from the evidence now 

 available. I am of the opinion, however, that it is not a 

 normal condition. 



Several had suggested that protoplasmic connections 

 or plasmodesma are of importance in transmitting stimuli 

 of one sort or another. Kienitz-Gerloff (1891) accepted 

 these and suggested further that the plasmodesma serve 

 as a path for rapid transfer from cell to cell of protoplasm, 

 colloidal material and soluble materials of large molecular 

 size, and although he seemed to think that most soluble 

 materials, including sugars, could pass readily through 

 plasmatic membranes, his suggestion as to the path of 

 transfer is valuable, even if one does not accept his sug- 

 gestion as to mass flow. It has long been recognized and 

 repeatedly demonstrated that plasma membranes are 

 relatively impermeable to many solutes, especially sugars 

 and even simple salts and ions. Steward (1930) has 

 clearly demonstrated this low permeability of living cells 

 to sugars. The presence of plasmodesma, however, form- 

 ing connections between living cells, would allow for ready 

 exchange between them without necessitating a movement 



