104 BOTANICAL GAZETTE [AUGUST 
disintegration of the protoplast and the disappearance of color take 
place in a few seconds. In neutral red alone the axial differences 
in susceptibility are similar to those in KCN, but death begins much 
later and proceeds more slowly. 
A few observations were made on the transparent hairs which 
arise from the cortical cells. These hairs contain no transverse 
cell walls, being merely cell outgrowths. In the long fullgrown 
hairs the susceptibility gradient is distinctly acropetal, while in 
those which are apparently still growing, it is basipetal. These 
differences suggest that while the hair is growing its apical region 
possesses the highest metabolic rate and the axial gradient is basi- 
petal, but that after growth is completed and the apical activity 
decreases, the gradient becomes acropetal, that is, from the cell 
with which the hair is connected. The possibte significance of this 
change will be considered later. 
Spyridia filamentosa.—Observations on this form are frag- 
mentary, since only a single thallus, detached and apparently not 
in perfect condition, was available for examination. Each main 
branch of the thallus, as well as each of the simple lateral branches 
which arise from it, shows in general a basipetal gradient; and each 
such system as a whole shows more or less clearly a basipetal gradi- 
ent from branch to branch, the most apical branches being most 
susceptible, the next lower in general less so, and so on. 
In the plant examined, however, irregularities in these gradients 
were frequent, both in single branches and in the whole system. 
Here and there cells were already dead, while others were more or 
less susceptible than their neighbors, and the same differences 
appeared between different branches in some cases. These irregu- 
larities probably indicate that the plant was not in good physio- 
logical condition; as previously noted, it was detached when 
collected and had been washed about by the waves, so that some 
of the cells had undoubtedly been injured or killed. The suscepti- 
bility of this species to KCN and to neutral red is in general very 
high, death beginning almost at once in KCN m/100, and within 
half an hour to an hour in neutral red alone. Since I have found 
that high susceptibility to the cyanides in animals indicates in 
general high susceptibility to at least many other depressing 
