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6. Their color (lighter on one side); markings; variations in 
form. (See demonstration microscope.) DRaw five different spores. 
While the chlamydospores of most smut-fungi are resting-spores, 
those of U. Tritict, on account of the blossom-infecting habit of the patho- 
gene, have largely lost their ability to remain viable for a long period. 
The dusty dry chlamydospores are scattered by the wind over the 
blossoming wheat. Some spores fall upon the exposed stigmas protruding 
from the open glumes of healthy heads. Here they germinate, sending 
a long germtube along and into the stigmatic filaments and by way of 
them into the young ovary. If germinating spores are available, study and 
OBSERVE —- 
7. The long germtubes, septate and with knee-joint fusions. 
8. The uniform absence of sporidia. 
DRAW several germinating chlamydospores to show variation. 
This germtube is morphologically a basidium which in most other 
species of Ustilago produces basidiospores or sporidia as they are called. 
In this species, sporidial production is unnecessary. After penetrating 
to the ovary, the germtube branches.and, establishing itself near the grow- 
ing-point, goes into a dormant condition along with the ripening kernel. 
The invaded kernel shows no evidence of injury. 
As the embryonic plant develops upon planting the kernel, the mycelium, 
aroused by the same condition of heat and moisture (and probably by the 
activities of the embryo as well), begins active growth, branches and spreads. 
into the stooling. culms, and forces its way upward through the tissue 
as the stem lengthens. When the wheat heads begin to form, the mycelium 
of the fungus tales possession, completely replacing the more tender 
or succulent tissues of the spikelet with its dense mats of profusely branch- 
ing mycelium, thus forming the black, easily ruptured sori of the smut. 
The diseased heads emerge from the sheath about the time the flowers 
on the healthy heads are in full bloom. Why? 
REPORT 
1. A farmer writes for information on the nature and control 
of the loose smut of wheat. Write him a letter giving clearly and concisely 
the information he needs. 
