432 BOTANICAL GAZETTE [JUNE 
by simple mechanical pressure aided by cellulose or pektose- 
dissolving enzymes. It has not been the writer’s observation, 
however, that the filaments penetrate to the interior of the cells 
to any great extent. Occasionally a case is seen as shown in 
fig. 2, but here there appears to be no dissolving or swelling of 
the wall, but a breaking through by simple 
mechanical pressure. The various other 
enzymes then become active and the tissue is 
completely destroyed. 
The question still remains as to the nature 
of the poisonous substance. It has already 
been mentioned, and is a well known fact, 
that the formation of oxalic acid almost inva- 
riably accompanies the growth of Botrytis, 
: Fic. 2-—Fila. being brought about by the oxidation of car- 
ment of Botrytis cin. bohydrates. Analysis of the mycelium extract 
kas oo a also shows this substance in considerable 
a oh amount. DeBary considered the possibility a 
: et thie ehateace being concerned in the effect of the fungus 
upon vegetable tissue, but discarded the idea on the ground that — 
solutions of pure oxalic acid do not give the entire character- 
isti 2¢ tt of a Botrytis extract or culture. The constant 
nc e of this substance has seemed to the writer at beast 
us estive, and its effect upon plant tissues has been studied 2 
extent. It is of course well known that oxalic. = 
lasmolysis and death of cells if sufficiently strong. — : 
tuce leaves were “ori by the writer with the petioles 
bmerged in Botrytis extract,and 0.125 per cent., 0.5 per vee 2 
and I per nt. oxalic acid. After a few hours of this treatment — 
aremarkably similar effect was observed. All showed marked 
rt ning: the tissue where touched by the liquid, followed by ee 
apse ant sh veli ane ‘The effect of the weakest solution © 
5 per c , was as marked ; as s that of the e ctrac a 
. ice in ‘effect to 
il In all five cases the affected re cit c 
ppearance of ie been ages, ‘The: chet - 
