438 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
not strong evolution of oxygen when exposed to light. As soon 
as the chlorophyll grains are loaded with starch and when con- 
verted into “ Bläschen ” or disintegrated they naturally cease to 
assimilate. Dehnecke erred in supposing that amyliferous 
leucoplastie chlorophyll grains never could assimilate; the stop- 
page of assimilation is more accidental than functional, and in 
many cases of merely temporary duration. 
In many young stems the chlorophyll grains are found in the 
form of thin green envelopes enclosing one or more starch grains. 
These are, according to Dehnecke, non-assimilatory chlorophyll 
grains from which the starch grains finally escape, leaving the 
thin green envelope as a chlorophyll * Blüschen," which finally 
disappears, new secondary chlorophyll grains being formed by 
protoplasmic differentiation. In investigations of this kind the 
effects of manipulation and section-cutting are liable to form a 
serious source of error, for the latter especially may cause sec- 
tions of living tissue to show chlorophyll grains as “ Bläschen ” 
which were originally in the intact tissue perfectly normal (see 
p.990). When, after the starch disappears, new normal chloro- 
phyll grains are seen, these are not new formations produced by 
protoplasmie differentiation, but are formed from the original 
starch-bearing chlorophyll grains. Thus in the living uninjured 
cells it can commonly be seen that one side of the “ Bläschen ” 
is thicker and distinctly green. In other cases this thickening 
forms a distinct but irregularly-shaped chlorophyll grain, which 
can finally be seen without any starch-enclosing envelope, but 
with the impression of where a starch grain has previously beeu 
on its inner concave surface. In Pellionia the amyliferous 
chlorophyll grains of the stem are reduced to thin, flattened, 
green plates, which are often almost invisible, but when the 
starch is removed they become round, normal, green, assimilating 
chloroplastids. The “primary” and “secondary” chlorophyll 
grains are therefore simply two different conditions of the same 
chloroplastid. In fruits, after the starch grains have been con- 
verted into sugar the chlorophyll “Bläschen” finally disintegrate, 
but in all cases where normal chlorophyll grains appear after the 
disappearance of the starch they are formed from chloroplastids 
previously present. The initial power of forming chloroplastids 
by protoplasmic differentiation seems to be present only in the 
embryonic condition of the cell and to be lost in post-embryonic 
and adult life. 
