378 
REVIEWS OF RECENT LITERATURE. 
Alten H., uni) Jannicke, W.— Eine Schddigung von Rosenblattern 1 
durcli Asphaltddmpfe: <Bot. Zeit., 49. Jalirg., Leipzig, Maroh 20, 
1891, pp. 195-199; Nachtrag zu unserer Mittlieilung iiher u Eine Schd¬ 
digung von Rosenblattern durcli AsphaltddmpfeP <^lbid ., Sept. 25,1891, 
pp. 649-650. 
What. Prof. H. Marshall Ward has done for the parasitic diseases of 
plants caused by Botrytis bas been accomplished by the authors of the 
present papers for a nonparasitic disease of rose leaves caused by 
asphalt vapor; that is to say, a rational and connected account has 
been given of the exact course of the malady. The rose leaves in a 
garden were injured in a very peculiar manner by asphalt vapor gen¬ 
erated during the construction of a neighboring street. The injury 
was noticed in a strip running 150-200 meters southwest from the 
asphalt kettles. The injury was seen after a rain accompanied by a 
northeast wind. During clear weather no injuries were observed. The 
injured leaves showed a pronounced browning of the upper surface, 
became withered, and finally fell. In many instances the twigs bear¬ 
ing such injured leaves also died. A remarkable fact was that only 
the upper side of the leaves exposed to the rain were browned. 
Inverted leaves were browned on their under surface. When one leaf 
lay over another the under one was free from injury. Microscopic exam¬ 
ination showed that only the epidermal cells were damaged, these having 
a brown, granular cell content. There was a great difference in the 
amount of injury to different plants; roses were injured most and then 
strawberries, while delicate-leaved begonias remained entirely sound. 
Such, in brief, were the symptoms of the disease, and to explain the 
exact manner in which the asphalt vapor caused the peculiar injuries 
was now the task of the authors. The action of poisonous gases (such 
as sulphurous acid) was excluded by the fact that only the upper sur¬ 
faces of uncovered leaves suffered. Sections showed that there was 
no appreciable deposit on the upper surface of the leaf, and conse¬ 
quently the damage was not due to a body mechanically carried down 
and deposited by the rain on the leaves. It then became clear that 
the injury must be due to a soluble substance brought down by the 
rain and absorbed by the leaves. Curiously enough, the character of 
the epidermal wall seemed to exercise no influence in the matter, since 
delicate begonia leaves were spared, while coarse rose leaves, with 
thicker-walled epidermal cells, suffered. One thing, however, was soon 
determined, and that was that the injury stood in definite relation to 
some substance held in solution in the cell sap. The amount of injury 
to the cells was found to depend upon the amount of tannin contained 
in them. This explaiued why begonia leaves were exempt, for they 
