162 
Journal of Agricultural Research 
Vol. XXV, No. 3 
perhaps thereby retarded. The results of these hydrogen-ion determina¬ 
tions show that the final alkalinity or acidity of a solution depends not 
alone upon the fungus growing upon it, but in part, at least, upon its 
composition. 
Table V .—Showing the change in hydrogen-ion concentration in the solutions, and the 
rate of maceration by the enzym in the mycelium and in the solution on which it grew 
Experi¬ 
ment 1. 
Experi¬ 
ment 2. 
Experiment 3. 
Media. 
Ph. 
Ph. 
Ph. 
Maceration. 
Con¬ 
trol. 
In¬ 
ocu¬ 
lated. 
Con¬ 
trol. 
In 
ocu- 
lated. 
Con¬ 
trol. 
In¬ 
ocu¬ 
lated. 
Solution. 
Hyphae. 
String bean decoction. 
4 - 83 
8. 21 
4.82 
7.62 
4.82 
8.26 
None in 48 hours. 
Complete in 32 hours. 
Prune decoction. 
( l ) 
5 - 52 
i 1 ) 
8.21 
3.85 
5 - 52 
3. 68 
3 - 8s 
5 - 52 
4. 62 
Complete in 24 hours 
Slight in 48 hours... 
Irish potato decoction. 
8.08 
8.17 
Complete in 6 hours. 
Carrot decoction. 
3 - 24 
5 - 73 
4. 88 
5 - 42 
4-88 
5 - 55 
Complete in 48 hours 
Complete in 32 hours. 
Turnip decoction. 
4. 81 
5 - 98 
4. 76 
6. 23 
4. 76 
7 - 99 
Some in 48 hours.... 
Complete in 24 hours. 
Sweet-potato -decoc¬ 
0) 
(*) 
4.89 
4. 61 
4. 89 
4. 62 
Complete in 48 hours 
Complete in 32 hours. 
tion. * 
Czapek's solution.... 
4 - 03 
2. 65 
4 - 05 
2. 69 
4-05 
2. 52 
Complete in 24 hours 
Complete in 24 hours. 
Pfeifer’s solution. 
Richard’s solution... 
Beef bouillon. 
3 - 53 
( l ) 
( l ) 
2. 92 
f 1 ) 
(*> 
3 - 4 i 
3- 27 
8. is 
3 - 14 
3- 12 
8.13 
3 - 41 
3 - 27 
8. 15 
3 - OS 
3 - 17 
8. 22 
Complete in 48 hours 
None in 48 hours.... 
.do. 
1 No growth. 
There was no maceration of raw sweet-potato disks in portions of the 
solutions which had been steamed before testing them, except in Czapek’s 
solution, which had a final P H of 2.52. There was a slight loss of coher¬ 
ence of the cells in this solution in 48 hours, which was probably due to 
the acid present in the solution. A careful study of the table reveals 
the fact that in no case, neither in the solution nor in the hyphae, was 9. 
vigorous cell-wall dissolving enzym produced. Only in one case, that 
of the hyphae grown in Irish potato decoction, was maceration com¬ 
pleted in less than 24 hours, which shows for the most part that a 
pectinase capable of acting upon sweet-potato tissue is only feebly 
produced by Botrytis cinerea. 
These data can not be used to substantiate or refute the work of 
Smith, who claims to have demonstrated the production of oxalic acid. 
Undoubtedly, the age of the culture would exercise some influence upon 
the amount of acid produced and Smith does not state the length of time 
he allowed his cultures to grow. The writers were unable to detect 
the presence of acid in the mycelium of a 7 days ' growth. The distilled 
water in which a quantity of mycelium was soaked for 3 hours at room 
temperature had a P H value of 6.8, which is practically neutral. 
Apparently Botrytis cinerea is very similar in certain physiological 
characteristics to some of the species of Rhizopus, which, although not 
normally parasitic on the sweet potato, produce an enzym, perhaps in 
a small amount, capable of dissolving the middle lamellae of sweet-potato 
disks. Botrytis cinerea does not secrete a substance which will act on 
sweet-potato tissue to the same degree that it will on some other vegetable 
tissues, as shown by Brown and others. Is there then a variety of pecti- 
nases secreted by different fungi which is more or less specific for the 
tissue of certain hosts? Since it is impossible to isolate these enzyms, 
