oct. 15,1925 Leaf spot of Maize Caused by OpTiiobolus heterostrophus 719 
125 jit in length, consequently extending nearly the entire length of 
the ascus within which they follow an irregularly sinuous course. 
Subsequent growth ensues both in length and diameter, so that the 
final dimensions are frequently more than double those indicated. 
The length of the spores thus comes to exceed that of the ascus, a 
condition which is made possible by the helicoid coiling of the asco- 
spores, the turns of which become increasingly close as maturation 
proceeds. After a rather tight arrangement has been effected, cross 
walls make their appearance, beginning at the upper end of the spore 
and proceeding downward. 
When a penthecium containing mature asci is crushed in a water 
mount, a brisk discharge of ascospores ensues. As might be expected 
because of their involved arrangement, the spores of each ascus are 
discharged simultaneously, the discharge always taking place from 
the apex, .and with enough violence to propel the spores a short dis¬ 
tance through the water, the helicoid coils thereupon slowly becoming 
relaxed in loose, sinuous curves. Judging from the instances in 
which dehiscence is impeded, frequently as the result of immature 
condition, discharge is preceded by some swelling of th6 ascus (fig. 5, 
B, C, D), and circumscissile rupture in the apical portion of the ascus 
wall (fig. 5, E). Intertwined spores in groups of four have occa¬ 
sionally been observed adhering to the tip of the beak of perithecia 
examined in place, leaving little doubt that normally the spores in 
each ascus are discharged through the ostiole simultaneously as a 
group. 
On being liberated, either naturally or by manipulation, the 
ascospores appear as filamentous structures distinctly fuliginous in 
coloration, tapering somewhat at the extremities (fig. 5, H. K). 
The constrictions at the septa which previously were not pronounced 
usually become more clearly accentuated, evidently as a result of 
some slight enlargement of the delimited segments. The contents 
are somewhat granular, especially immediately adjacent to the septa. 
In some instances a mucous envelope is apparent (fig. 5, L, M). 
When properly mounted in water the spores germinate very promptly 
by the production usually of one to eight germ tubes which may 
originate terminally from the tip or laterally from any part of the 
spore (fig. 5, F. G). 
It should be mentioned that while the number of spores in an ascus 
is typically four, cases in which only three are present are by no 
means rare, and even one-spored and two-spored asci may be en¬ 
countered occasionally. In the latter instances the asci are less com¬ 
pletely occupied, the helicoid turns are looser and more irregular, 
although the direction of rotation remains the same. In cases of 
frustrated dehiscence, where the spores are only partly liberated from 
the ascus wall, germination is not materially impeded, the germ 
tubes arising from the lower segments of the ascospores perforating 
the surrounding membrane without any apparent difficulty. 
Cultures made by placing fresh asci on corn-meal agar plates and 
transferring the resulting growth to sterile agar slants, show the 
same type of growth and produce the same type of conidiophores and 
conidia as are found on cultures originating from conidia. Conidia 
obtained from such cultures when applied to maize foliage have been 
found to give rise to lesions indistinguishable from the lesions result¬ 
ing from the use of conidia from other sources. The facts regarding 
