40 BOTANICAL GAZETTE [JANUARY 
URSPRUNG (35-37) holds that Drxon’s idea that poisonous 
substances are carried to the leaves from the heated portion cannot 
be the correct one, since he finds that poisons such as CuCl, cause 
fading in quite a different way from that which occurs in the case 
of leaves on heated stems, and very much more quickly than is 
caused by a decoction of the stem supplied to the leaves in the 
manner described by Drxon. I can see no reason whatever for 
supposing that a metallic poison should have the same effect as the 
toxins which may be engendered by heating the stem, nor that the : 
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time required should be the same in both cases. By placing the 
faded leaves of an Impatiens branch, which had stood in a decoction, 
in a moist atmosphere, URSPRUNG observed that they soon regained | 
their turgescence. He thinks this shows that the leaves are not 
affected by plasmolyzing substances of a decoction of the plant. 
It may be, however, that these substances exert their plasmolyzing 
influences more slowly, and that the turgescence may be recovered 
if the leaves are not dead. It is well known that leaves may undergo 
a very marked degree of wilting and still recover their turgescence. 
SCHROEDER has shown that most leaves can lose as much as one- 
half of their water content without severely suffering. 
SCHROEDER (27), in studying the symptoms of death as a result 
of wilting, finds that in most leaves a discoloration occurs, due 
to an oxidation of the tannin content. He also observed that in the 
early stages of death the chloroplasts move to one end of the cell 
or toward the middle; they round up and lose their typical color 
and structure. The protoplasts finally contract, the plastids take 
on a glassy appearance, and Brownian movements are observable 
in the cell contents. In the microscopical studies which I have — 
made of the leaves on steamed stems, I have found many of the 
same conditions described by ScHROEDER, all of which indicates 
that these leaves are dying, not so much, it seems to me, from 4 — 
lack of water as from the effect of some harmful substances. He 
finds that the rate of loss of water decreases from the beginning 
to the end of the process. The amount given off during any one 
interval is never greater than that of the preceding one. Death 
of the leaves greatly modifies the successively decreasing rate of s 
water loss during wilting. The first 50 per cent of the fresh weight 
