46 Research Bulletin No. 1 
Width. Length. 
0- septate 3.2 mu. 8 to 11 mu. 
1- septate 3.2 to 5 mu. 11 to 20 mu. 
2- septate 3.2 to 5 mu. 12 to 22 mu. 
3- septate 4 to 5 mu. 17 to 22 mu. 
On potato plugs in the light. 
Width. Length. 
0- septate 3 to 5 mu. 11 to 16 mu. 
1- septate 3 to 5 mu. 10 to 18 mu. 
2- septate 3 to 5 mu. 16 to 22 mu. 
On potato plugs in the dark. 
Width. Length. 
0- septate 2.4 to 3.3 mu. 8 to 13 mu. 
1- septate 3.2 to 5 mu. 10 to 20 mu. 
2- septate 3.2 to 5 mu. 18 to 25 mu. 
3- septate 5 mu. 22 to 25 mu. 
The greatest spore length noted was 40 mu. This spore was 
3 mu wide. The greatest width noted was 5.8 mu. The great 
majority of all spores measured is 5 x 17-20 mu. 
In measuring spores the diameter of the septum was meas 
ured, which gives a reliable basis for width determination. In 
measuring the length, the length of the segment between the 
two extremities was measured rather than the length of the arc 
of the curvature of the spore. 
The spores of Fusarium solani, as to length, compare most 
closely to those of Fusarium tuberivorum, but they are longer 
than we find the spores of the latter to be. They also are a trifle 
wider than the spores of Fusarium tuberivorum. The only other 
species which could be confused with Fusarium tuberivorum is 
Fusarium orthoceras. The spores in this species are too narrow, 
however. Neither Fusarium solani nor Fusarium orthoceras 
gives the percentages which would make it possible for any one 
to confuse the three species. The percentages of Fusarium solani 
according to Appel and Wollenweber are: 
1- septate 8 to 0 per cent. 
2- septate 14 to 0 per cent. 
3- septate 67 to 90 per cent. 
4- septate 16 to 0 per cent. 
5- septate 6 to 0 per cent. 
