66 Report OF THE BOTANIST OF THE 
Besides these direct observations there are several other good 
reasons for believing that the ruptures were not made at the 
time of freezing, as held by Sorauer. One of the best of such 
reasons is the fact that where the ruptures occur the paren- 
chyma is invariably strongly arched. Had the rupture occurred 
at the time of freezing, the growing parenchyma would have 
been free to spread out flat in a normal manner. 
It has already been stated that the breaking of the blisters 
and the consequent exposure of the parenchyma cells sometimes 
resulted in the death of the cells and the formation of dead, 
brown spots; while in other cases the parenchyma cells ap- 
peared to be entirely unharmed by their exposure. On June 
13th an unsuccessful attempt was made to produce the dead 
spots artificially by rupturing the epidermis over several blis- 
ters on four different leaves. In every instance the exposed 
cells continued green through the remainder of the season. 
This was a surprise. It seemed scarcely possible that the 
loose, thin-walled mesophyll cells could bear prolonged exposure 
to the air; but it is an indisputable fact that such was the case, 
and hundreds or even thousands of examples of it could be 
found on almost any affected tree. It should be considered, 
however, that the season was unusually wet and cool. 
It appears that the dead spots were formed early in the 
season. It may be that the cells when young were less able to 
bear exposure. We cannot agree with Sorauer that the cells 
were killed at the time of freezing. It is more likely that they 
died later from excessive transpiration after the epidermis had 
been ruptured. According to our observations the -lower epi- 
dermis on the dead spots was invariably ruptured. The large 
size of some of the dead spots indicates that they enlarged con- 
siderably after the freeze, and this could not have happened had 
the cells been killed in freezing. 
ON OTHER PLANTS. 
The same phenomenon was observed on quince leaves, but to 
a less extent. The wrinkling of the leaves on the upper sur- 
face, the separation of the lower epidermis from the mesophyll, | 
