147 
APPARENT REVERSIONS 
In several instances where colony color, aerial mycelium, or partial 
sterility was the saltant character, small sectors of the colony were so 
changed as to resemble closely the originals, and as far as tests were applied 
could not be distinguished from them (Pl. XXXII); in no case, however, 
where true saltant character was proved by constancy through several trans- 
fers did the whole stock revert; what appeared as reversion was limited to 
occasional sectors of the colony, and in no case did such change occur in 
the entire margin of a colony. 
SUPPOSITITIOUS CAUSES OF THE VARIANT SECTORS 
Several alternative suppositions other than that of saltation may be 
briefly discussed as possible causes of the variant sectors. The mycelium 
at a certain point may become weakened, or die, and the change in equilib- 
rium resulting may cause the variant sector. Spores of another Helmin- 
thosporium or of some other organism may fall into the colony from the air, 
and the variant sector may represent merely a contamination. The in- 
oculum used on a plate that shows saltation may have consisted of more 
than one strain or elementary species of Helminthosporium. The first 
supposition is open only to crude experimentation, while the second, if 
valid, implies a wonderful Helminthosporium-richness in the air of my 
laboratory as well as very faulty technique. Since saltation occurred after 
the fungus, H. No. 1, had been transferred many times by lifting a small 
bit of agar from the edge of a colony, the presumptive evidence that no 
mixture then existed is very strong. The following experiments bearing 
on these suggestions may, however, be worth recording. 
Wounding.—A culture of H. No. 1 on corn-meal agar was allowed to 
grow to a diameter of about 4cm. Then by means of a hot iridium wire 
the mycelium was killed at the points indicated in Pl. XXIX, above. In 
all cases the uninjured parts soon entirely outgrew the wounds, and the 
whole colony presented an entire, normal outer border with no evidences of 
saltation. In some instances a clear straight line extended from the point 
of wounding nearly to the edge of the colony. Evidently disturbance 
of equilibrium such as this did not cause saltation. 
Mixed planting.—Acting on the knowledge that the saltants were 
frequently slow-growing, and thinking that possibly ordinary transfers 
might be mixtures of two or more races, of which the slower-growing one 
ordinarily remained masked, M8, a well-characterized saltant, was planted 
