119 
Mere casual observation of many strains of Helminthosporium showed 
that the point of maximum diameter was usually near the basal region of 
the conidium, occasionally near the middle region, while in extremely rare 
cases it was near the apical quarter, the ratio of these cases being for H. 
No. 1 about 30:14:4. A more accurate determination of what may be 
termed the longitudinal eccentricity of the conidium—that is the range 
of variation in the position of the line of greatest diameter (a—a’, Diagr. 
I—IV) may be made by measuring (along the longitudinal axis) the dis- 
tance from the base of the conidium to the intersection of the line a—a’ 
with the longitudinal axis. This distance divided by the total length of 
the conidium may be known as its coefficient of longitudinal eccentricity. 
This coefficient for H. No. 1, based on 65 conidia taken at random, was 
found by the above method to be .43+0. In other terms the point of 
maximum diameter was distant from the base of the conidium 43% of the 
total length of the conidium. Bakke (6) says that the conidia of H. te- 
ves are widest at the middle. The coefficient of longitudinal eccentricity 
based on 11 conidia of H. No. 1 which were of typical subcylindrical ap- 
pearance (approaching that shown in Diagr. IV) was .45 as contrasted with 
a coefficient of .43 for 11 conidia of elliptical appearance (Diagr. I). Co- 
efficients of longitudinal eccentricity for H. Nos. 5, 20, and 4 of subcylin- 
drical shape, were respectively .35, .39, and .37, showing that in these 
forms the point of maximum diameter is slightly nearer the base than it is 
in H. No. 1. None of the conidia of H. No. 1 was truly cylindrical, 
that is, the sides were not parallel for any appreciable distance. Many 
were subcylindrical, the form approaching that shown in Diagram IV. Of 
65 conidia taken at random 81%-+ of the conidia were elliptical; 17%-+ 
subcylindrical; and 1% otherwise. 
To secure a coefficient which would indicate with some degree of ac- 
curacy the curvature of the conidial wall (as from point a to point y, Diagr. 
xy 
h 
I—IV) determinations were made of the ratio : (Diagr. I—IV). The 
line cd was tangential to the surface of the conidium at the point of maxi- 
mum diameter, and was parallel to the longitudinal axis of the conidium, 
the line ef being 3.4 « from the line cd and parallel to it. Then the points 
x and y are where the surface-line of the conidium cuts the line ef. It is 
obvious that as the line xy increases in proportion to the length of the conid- 
ium, gh, the conidium more nearly approaches the form of a cylinder; and 
as the line xy becomes proportionately shorter the conidium becomes less 
: : ae) She 
like a cylinder. The ratio on may therefore be termed the coefficient 
