24° BOTANICAL GAZETTE [JULY 
ment of the parasite took place until the plants began their natural 
loss of vitality at maturity, and under these conditions, when little 
nourishment was left for an active parasite, only teleutospores 
appeared. 
Another side of the relation of Puccinia Asparagi to water was 
brought out particularly by Sirrine,? who, from his observations in 
New York, was led to conclude that the relation of the rust to atmos- 
pheric moisture in the form of dew or fog was the most important 
factor of this nature in the development of the disease. In the cases 
described by this writer the progress of the fungus seemed to be 
accelerated by excessive dew-fall, while with the absence of the latter 
the rust was less prevalent. In an asparagus bed upon a sloping 
hillside, for instance, the most rusty portion was at the base, decreas- 
ing with the rising grade. It has also been frequently observed that 
asparagus growing in the shade, as where a tree stands in the midst 
of a bed, remains free from rust when all about it is dead with the 
disease. This fact shows certainly that the protection thus afforded 
prevents infection by the fungus, and can be explained only on the 
ground of the prevention of dew being deposited. Stone and Smith 
maintained, however, that under ordinary conditions no such differ- 
ences existed in their section as were observed by Sirrine, since some 
of the least rusted beds were in regions most subject to heavy dews, 
and in the case of asparagus growing on a slope, that at the bottom was 
likely to be least affected, on account of the usually heavier soil there. 
They held in regard to the influence of dew that, ‘when plants are 
not resistant enough to stand uredospore infection, it is not difficult 
to understand how this might take place, but the presence of any 
amount of dew fails to infect some beds in this. state;” the beds 
referred to being those in heavier soil. 
In the writer’s opinion both of these theories as to soil and atmos- 
pheric moisture were correct, but modified by local conditions. In 
showed from the first more decided differences in susceptibility to 
the rust than in any other section. These conditions were studied 
with great thoroughness by field observation and mechanical analysis 
of soils all over the state, and the conclusions arrived at have been 
? Bulletin 188, N. Y, (Geneva) Exper. Station. 
' 
' 
, 
