ANTHRACNOSE OF CUCURBITS. 61 
is of interest to note that the 1915 seed was apparently as free from 
disease as treated seed. All of the treatments appear to have been 
effective in these field tests. 
The effectiveness of formaldehyde, 1 per cent for 20 minutes, and of 
mercuric chlorid, 1 to 1,000, for 5 minutes, was tested in the laboratory 
by avoiding contamination after sterilization and planting the seed 
in culture media. One test was made on seed previously inoculated. 
In all cases, however, the effect upon the normal surface flora of the 
seed was used as a criterion. The results of these tests are presented 
in Table XI. 
TaBLE XI.—Laboratory tests of the treatment of cucumber seeds with mercuric chlorid and 
formaldehyde for the control of anthracnose. 
Mercurie chlorid. Formaldehyde. 
Date, 
SEO Dsisk 1917. Method. Num- Num- 
ber Results. ber Results. 
tested. tested. 
Ohiogeteeee PA DIoee On| OR DEL ACE Mtn Ge xa. |se= eet Nata? o 8 Okan age 20 | 10 sterile; 1 with fun- 
wos agar, in gus; 9 with bacteria. 
ate. 
Inoculated |_..do..... i AG Pend Bae <a 20 | PAUistenile seme ae 20 | 4 sterile; 4 with fungi; 
on Mar. 12 with bacteria; no 
13, 1917. anthracnose. 
DOs soo2 Wine 1B os a58 ue An ere 30 | All sterile except one; 40 | None sterile; 7 with 
anthracnose on coty- fungi; no anthrac- 
ledon. nose. 
1D KO) oe ss ee ee eae Bouillon tubes. - 10 | 9 sterile; 1 developed a |..-.... 
fungus. 
ID KO) Sel ie aac Nutrient agar - -- NG} AU SIGMD so. ecccedesH |ssoseen 
These results show that the mercuric-chlorid treatment is more 
reliable than the formaldehyde in absolute effectiveness. The very 
interesting case in which 1 out of the 136 inoculated seeds yielded 
a diseased seedling deserves some comment. The age and location 
of the lesion indicated that it had resulted from a recent spore infec- 
tion rather than an earlier micropylar invasion. This would mean 
that the spore had not only escaped the germicide but had also 
survived two months of desiccation. It was probably lodged in 
the micropyle and protected from the germicide by an air bubble. 
Owing in part, no doubt, to organic matter on the seed, there is a 
marked decrease in the strength of mercuric-chlorid solutions after 
seed is immersed therein. Six liters of seed decreased the concen- 
tration of mercuric chlorid in eight liters of the germicide by almost 
one-half. This means that the solution can be safely used only 
once or twice. | 
The effectiveness of a 5-minute immersion in weaker solutions has 
been tested by the agar-plate method. Using about 100 seeds for 
each series, the following percentages of sterile seeds were obtained: 
Mercume chionids gly tole 500: sees fat ee 99 per cent sterile. 
IMercunickehloridealton: O00 si nasties erate: 94 per cent sterile. 
Mencurieychiond. tos 0008s 2.22 ea Oh ee 97 per cent sterile. 
