IN VEGETABLE BIOLOGY. 223 
bered that the positive critical point of aquatics is situated much 
further to the left of the photrum than is that of aerophytes. 
What does this mean? Obviously, that the protoplasm of the 
former is more sensitive to light, or, in other words, that light is 
capable of imposing a greater strain upon it. We should con- 
sequently expect that the protoplasm of aquatics would recover 
from the effects of the strain more slowly than that of aerophytes, 
or, to use the language of electricity as applied to the “ residual 
charge" on a Leyden jar (a phenomenon now believed by elec- 
tricians to be only another instance of elastic recovery), the 
“charge” of light would more readily “soak out” of the aero- 
phytic than out of the aquatic protoplasm. It is submitted, then, 
that so long as a darkling plant has its grains in epistrophe, so 
long, even though it may have been imprisoned weeks or months, 
do the motile effects of moderate illumination upon its proto- 
plasm remain manifest*. Moreover, the behaviour of the posi- 
tively apostrophized grains of aquatics and aerophytes set in 
darkness is a pure enigma, unless viewed from some such stand- 
Point as is here taken up. When a leaf of Funaria with posi- 
tively apostrophized grains is deprived of light, no appreciable 
alteration in the position of the chlorophyll occurs, and appa- 
rently for the following reasons. Two actions are now in opera- 
tion, viz. recovery of the protoplasm from the extra strain of 
apostrophization (this would of itself tend to epistrophize the 
grains), and the elimination of the disturbance induced by epi- 
strophization (which would, if it acted alone, result in driving them 
on to the lateral walls). Although, as is shown in the table on 
P- 234, epistrophization from positive apostrophe takes less time 
than negative apostrophization from epistrophe, which would 
lead to the surmise that some tendency to epistrophe ought to 
be seen if the theory be sound, yet it must not be forgotten 
that signs of apostrophe soon manifest themselves in darkling 
Funaria-leaves, full apostrophe under exceptional conditions 
being established in the short space of one hour. It may there- 
fore be safely assumed that soon after an insolated Funaria-leaf 
* I hope upon a subsequent occasion to deal with the fructifying causation 
of light in a detailed manner. It must here suffice to mention Strasburger's 
discovery (Jenaische Zeitschr. 1878) that many phototactic zooepores for a short 
While continue to move, after a sudden change in the intensity of light, in the 
direction due to the former illumination: this phenomenon, closely similar to 
the slow soaking out of motile effects in darkness, is well reproduced in rotation. 
