Mar. 25, rors Dissemination of Chestnut-Blight Fungus 519 
The aspirator tests do not appear to have given as reliable results as 
the exposure-plate method, since it may be noted from Table XV that 
negative results were obtained on certain days when the exposure plates 
showed that ascospores were prevalent. The importance, however, of 
the aspirator tests lies in the fact that ascospores were obtained under 
perfectly natural conditions in the field at a distance of 13 feet from the 
nearest lesion and that they were obtained at times when ascospore 
expulsion was taking place. 
WATER SPORE-TRAP TESTS 
The use of water spore traps for testing the transport of spores of the 
chestnut-blight fungus by the wind was the outcome of our attempts to 
use the method of Burrill and Barrett (3) in their study of the wind 
dissemination of Diplodia zeae. First, substituting a funnel for the glass 
plates employed by the writers just cited, an attempt was made to find 
some mixture which could be applied to the inner surface of the funnel 
and which would fulfill the necessary requirements, as follows:. 
1. The mixture must contain no substances toxic to spores of the 
chestnut-blight fungus. 
2. It must spread readily and adhere to a glass surface. 
3. It must be sticky, so as to retain the spores which lodge upon the 
surface, which is coated with it. 
4. It must retain its sticky character at least 24 hours under field con- 
ditions. 
5. It must be readily soluble in water. ; ; 
Glycerin of various percentages was tried alone, as well as in combina- 
tion with various quantities of gum arabic or gelatin, but in all cases the 
mixtures either dried too soon ‘or did not spread well on a glass surface. 
The fact that pycnospores do not germinate in water (4) suggested the 
substitution of dishes of sterile water for the funnels. The first idea was 
that analyses of the water from these dishes exposed in the field under 
natural conditions could be made at intervals of some days and would 
reveal the presence of pycnospores if they had been carried by the wind. 
Experience in the field, however, proved that the method was also well 
adapted to the study of ascospore dissemination. 
DESCRIPTION OF THE WATER SPORE TRAPS 
A water spore trap consisted of a crystallizing dish 5 cm. deep and ro to 
12 cm. in diameter, into which sterile water was introduced. The dishes 
were wrapped in paper and sterilized in the laboratory for transport to 
the field. Each dish was supported about 2 feet above the ground by a 
tripod of three small stakes driven into the ground. ‘Ten-penny nails 
were driven into the ends of the stakes, whose ends were converged to 
make a support for the dish. The nails were held in proper position 
by a heavy cord attached to them and encircling the dish. By this 
means they were so firmly secured that they were never in danger of 
being blown out by the wind (Pl. LXIV, fig. 3). After placing a dish in 
its proper field location, 100 to 150 ¢. C. of sterile water were introduced. 
Water for this purpose was kept in stock in small Erlenmeyer flasks. 
The dishes of water were exposed in the field in various selected loca- 
tions and analyses made at certain intervals (fig. 3; also Pl. LXV, figs. 
1 and 2). 
