LLOYD: GROWTH OF PROTOPLASM IN POLLEN TUBES 87 
Growth took place in alkali also in a greater range of concentra- 
tions, namely, from N/400 to N/25,600, and it was determined 
that the Na-ions penetrated the protoplast. In N/400 the growth 
was less than in the control, this, it is possible, being related to an 
incregse in salts formed. At all other concentrations the amount 
of growth was greater than in the control, increasing from the 
lowest concentration used to /V/3200 and falling for those still 
higher. 
The failure to obtain positive results with certain acids in 
terms of growth, as above stated, need not, indeed should not, be 
interpreted except as indicating that other effects antagonistic to 
normal behavior intervene. 
We may note especially the bursting of the protoplast beyond 
the confines of the cell wall. The weakest point in the pollen-tube 
wall is at the apex, and it is here that bursting takes place if it has 
not already occurred before growth begins. Bursting is due to the 
imbibition of the protoplast beyond the strength of the wall to 
confine it, and not, as might be expected, to any change in the wall 
itself, such as hydrolysis, since the bursting takes place more 
rapidly at concentrations of the reagent which would cause less 
hydrolysis. 
In acids the bursting takes place within a certain range of con- 
centrations, namely, those above that at which maximum growth 
takes place and below those at which syneresis of the protoplasm 
is caused. Syneresis is quite evident in all the acids studied at 
concentrations at or above N/3200, and it is of more than passing 
importance that syneresis occurs in formic, oxalic, and hydro- 
chloric acids at lower concentrations (1/3200 to N/1600) than іп 
citric, malic, and acetic acids, and was not observed at all in 
alkali. It is evident in the course of a short time in the highest 
concentrations (N/800 to N/400) but ensues more slowly in the 
lower effective concentrations. It should be stated that in all 
these the protoplast swells fully when first subjected to them, 
completely distending the pollen-grain walls. It then slowly 
shrinks. : 
At the close of shrinkage it can be shown that the protoplasm 
is coagulated, for on pressure it breaks out as a cheesy mass. In 
this connection it is important to note that at the higher concen- 
