274 
Journal of Agricultural Research 
Vol. II, No. 4 
other averages with deviations from the first series would be obtained. 
With the same fungus on other substrata we may get still more devia¬ 
tions. In summarizing all results, we get the fluctuations of the average 
size. Experience has shown that we do not need hundreds, but merely 
io spores from each different culture condition in order to get the normal 
fluctuation of the average size. 
Hypomyces ipomoeae (Hals.) Wollenw. from roots of Ipomoea batatas 
gave in pure culture the following average fluctuation of various stages: 
Culture 30 days old on steamed potato tuber: 
Perithecia, 250 by 200/1; ascospores, ix by 5 to 5.5/4; 3-septate conidia, 33 by 
4.25/1 (6 per cent); 4-septate, 42 by 4.75/1 (1 per cent); 5-septate, 55 by 5.25/1 
(56 per cent); 6-septate, 61 to 5.5/1 (31 per cent); 7-septate, 66 by 5.5/1 (5 
per cent); 8-septate (1 per cent). 
Culture 30 days old on steamed potato tuber: 
Perithecia, 365 by 302/1; ascospores, 13 by 5.75/1; o-septate conidia, 12 by 3.5/1 
(30 per cent); 3-septate, 33 by 4.25/1 (60 per cent); 5-septate, 49 by 4.75/1 
(10 per cent). 
Culture 23 days old on wheat heads: 
Perithecia, 296 by 253/1; ascospores, 13 by 5/1; o-septate conidia, 12 by 3.25/1; 
3-septate, 36 by 4.5/1; 5-septate, 60 by 5.25/1 (90 per cent); 6-septate, 66 by 
5 - 25 /*- 
Culture 45 days old on cotton stem: 
Perithecia, 290 to 338 by 197 to 223/1; ascospores, 12 by 5/1; 3-septate conidia, 
35 by 4-25/* (38 per cent); 4-septate (35 per cent); 5-septate, 59 by 4.5/1 (25 
per cent); 6-septate, 58 by 5/1 (1 per cent). 
Culture 14 days old on straw; overwatered: 
Perithecia not measured; 5-septate conidia, 10 by 5.5/1 (100 per cent). 
Culture 14 days old on boiled rice: 
Perithecia absent; conidia unicellular, 6 to 10 by 3 to 4.75/1. 
Culture 20 days old on sterile water: 
Chlamydospores, 7 to 10/x; originated from conidia. 
The average size was higher in the presence of water than under dry 
conditions, but the number of septations could occasionally be decreased 
by overwatering. This table shows the fluctuation of average size and 
percentage of equiseptate conidia, indicating that 5-septate conidia 
prevail, being closely followed by 3-septate ones. Of all conidia 31 per 
cent may be 6-septate, 10 per cent 7-septate, 1 per cent 8-septate, but this 
is very seldom, and 3- and 5-septate spores will always be predominant 
in maturity. Young cultures bear more unicellular than septate conidia. 
The average size of equiseptate conidia is more constant than that of 
unequiseptate conidia. The perfect form of the fungus offers less difficul¬ 
ties, although fluctuations in the average size of perithecia may be con¬ 
siderable. Ascospores fluctuate but little, except when immature spores 
are included in the measurements. These measure 3 to 5.75/rin diameter, 
while mature ascospores average from 4.5 to 5.75//. 
The following list of ascomycetes shows the relationship to Hypomyces 
ipomoeae: 
