A Dry Rot of the Irish Potato Tuber 
21 
all show a great preponderance in the number of the one-septate 
spores. This number ranges from 40 to 98 per cent according to 
the age of the culture, the one-septate spores increasing in number 
while the two- and three-septate spores decrease in number with 
the aging of the colony. 
The results show that for a definite medium under definite 
conditions the percentages of the number of septations are a 
reliable character. Appel and Wollenweber distinguish an "An," 
"Norm," and "Ab-Kultur" and a "Jung," "Hoch," and "Alt-Kul- 
tur." The conidia which are produced from the mycelium of an 
original isolation inoculation would be "An-Kultur" conidia. 
These are unfit for character studies. When such conidia of the 
"An-Kultur" are used as inoculum, the resulting culture is a 
"Norm-Kultur," which can be maintained for a long time by 
repeated transfers. If degeneration should set in, the "Ab- 
Kultur" condition would result. Thev divide the "Norm-Kultur" 
into "Jung." "Hoch," and "Alt-Kultur." In the former the conidia 
may be abnormally large or small and irregular in form, con- 
sequently not suitable for measurements and form study. In 
the "Hoch-Kultur." which sets in after a period of eight to four- 
teen days, the greatest uniformity is noticed and this condition 
may last for a month. Poorly developed forms which develop 
late in the "Norm-Kultur" constitute the "Alt-Kultur." 
No striking differences in the appearance of the conidia were 
found in the various cultural stages of Fusarium tubcrivorum 
excepting poorly developed conidia which can be placed in the 
"Alt-Kultur." All of the work was done with the organism in 
the "Hoch-Kultur" condition so that there might be uniformity 
in the data. In the "Alt-Kultur" the spores dry up, curve con- 
siderably, and often one end cell becomes very pointed and 
hyalin. When this condition is reached the percentage of one 
septate conidia is very high, 85 to 95 per cent. At times cells 
of such a spore seem to have varying amounts of plasma, one 
remaining plump and round and the other drying up and be- 
coming pointed. 
The percentages of numbers of septation per spore are sur- 
prisingly constant, but can be influenced by changes in the en- 
vironmental conditions. Especially is this the case when the 
temperatures are varied. (Tables 2 to 5, Graphs 1 to 4.) 
Counts have repeatedly been made of the number of spore 
septations of Fusarium orthoccras, of Fusarium tubcrivorum, 
and of what may be another Fusarium which attacks Colorado 
potatoes, and we find that for these three species the counts of 
the number of septation of the spores would be sufficient to 
separate them. When in addition one makes use of other char 
