July is, 1914 
Fusarium on Sweet Potato 
277 
all descriptions have been based on field material and not on pure cul¬ 
tures, a few supplementary notes and illustrations may be desirable in 
order to show how much the conidia of this fungus differ from some 
species of Fusarium often associated with them in the field, and how 
slender the ascospores are compared with those of Gibberella pulicaris t 
a fungus often confused with G . Saubinehi . Attention has already been 
given to these points in this paper, and the conduct of this fungus in 
pure culture has been freely discussed in “Criteria of the norm.” 
In Table I a record of some measurements is given. The conidia have 
a range of septation differing with age and substratum, but 3-to 5-septate 
conidia prevail under various conditions. The average size varies greatly 
if the septation is neglected, but equiseptate spores fluctuate in small 
limits only. If we measure the absolute fluctuation of the size, we get, 
of course, a wider limit. For instance, the absolute size of 3-septate 
conidia in a 40-day-old culture on steamed potato stems fluctuates from 
21 to 39 by 3 to 5.5/* in one preparation, from 24 to 36 by 3.4 to 5.1/4 in 
another, while the average size based on the average of 10 measurements 
was 30 by 4.25/1. This fact proves an almost general law, which could 
be given in the rule ‘ ‘ The absolute fluctuation of the spore size is a func¬ 
tion of the average fluctuation.” If 20 per cent of its value is subtracted 
from and added to 30/*, the result is 24 and 36/4. The same operation 
extended to 30 per cent gives 21 and 39/*. The breadth, 4.25, treated 
in the same way gives 3.4 and 5.1 /* in one, 3 and 5.5/4 in the other case. 
When the fluctuation of the average size of 3-septate conidia has been 
obtained, 30 to 46 by 4.25 to 4.5/4, and desire an approximate idea of 
the absolute fluctuation, the mean proportional, which is 38 by 4.375/*, is 
taken, 30 per cent added and subtracted, and about 27 to 49 by 3 to 5.75/* 
is obtained, which corresponds almost with the fact. For this reason 
the absolute fluctuation, given by Appel and Wollenweber (1910) is 
left out as superfluous in the diagnoses of this paper. 
Tabi<£ I .—Fluctuation of the average sizes of the conidial and perfect stages of Gibberella 
Saubinetii based on the average of 10 measurements 
Conidial, Stags 
Age 
of 
cul¬ 
ture. 
Pure culture 
on steril¬ 
ized— 
Average length, breadth, and percentage of equiseptate conidia. 
0 to 2-sep- 
tate. 
3-septate. 
4-septate. 
5-septate. 
6-septate. 
7-septate. 
Days. 
1 .... 
12.... 
Potato stem. 
.do. 
pt 
P. 
ct. 
f fi 
36 by 4.5 
37 by 4.5 
33 by 4-5 
3 oby 4.25 
3 7 by 4.50 
46 by 5 
P. 
ct. 
18 
30 
8 
68 
50 
38 
a 
P. 
ct. 
11 
19 
23 
22 
12 
19 
* 
50 by 5.251 
52 by s 
45 by 5 
P. 
ct. 
70 
40 
69 
8 
21 
27 
M 
P. 
d. 
1 
4 
fit 
P . 
ct. 
1 
30.... 
.do. 
43 by 5 
40 .,.. 
.do. 
2 
12 
9 
* - * 
3.. .. 
7.. .. 
6.. .. 
6.... 
40.... 
40.... 
Potato tuber 
Potato tuber 
(pionnotes). 
Wheat straw 
Nutrient agar 
Wheat ker¬ 
nels. 
Rice. 
47 by 4. 75 
60 by 5.5 
56 by 5. 25 
54 by 5.5 
49 by 4. 75 
45 by 4.75 
3 
6 
2 
1 
64 by 5. 7 
71 by 5. 75 
7 
29 
SS 
24 
26 
23 
10 
35 by 4.25 
3 *by 4 .s 
45 by 4.5 
4 iby 4.75 
.3 
16 
