Lutman—Life History and Cytology of the Smuts. 1205 
in sections not showing quite as many fragments of mycelium. 
The hyphae (Figs. 11-12) at this time are very much contorted, 
of varying diameter, the cells multinucleated, and almost en¬ 
tirely intercellular (Fig. 9). The young leaves are full of the 
hyphae (Fig. 8) and even those that have lengthened may show 
the presence of the fungus up nearly to their tips. Many of the 
hyphae in the leaves are found to be intracellular in contrast to 
those nearer the axis of the plant. This is in plants six weeks 
to two months old in which the leaves are fairly well developed* 
Of course, no indication of spore formation appears in any part 
of the oat plant at this time. 
At flowering time longitudinal sections (Fig. 10) through the 
young infloresence showed the fungus in the older flowers as 
young spore pustules. The younger flowers show all stages in 
the development of the smut spores. 
The characteristic of this smut in addition to its smooth 
walled spores is that it does not convert the entire flower into a 
dusty mass hut forms pustules of rather small size which, ass 
they do not run together, do not destroy all the cells of the 
flowering glumes. The glumes thus retain the shape of the 
flower and keep the spore mass from becoming entirely diffuse. 
Spore formation can be traced in all its stages in a single panicle 
fixed at the proper time (Fig. 10). Sometimes the flowers near 
the tip remain immune while the ones below them are attacked 
indiscriminately especially the older ones near the base. At 
this time the rudiments of the glumes and sometimes of the 
t stamens are still to be distinguished but the smut seems to make 
no discrimination as to which tissue is attacked first in forming 
spores. ISTone of the floral parts ever come to maturity except 
the glumes; all the other are converted into spores before they 
are fully differentiated. 
The first indication of spore formation in the fungal hyphae 
is a much branched and contorted condition of some of the hy- 
phal tips. These are at the time intercellular and this knotting 
up of the hyphal tips frequently occurs at the angles of the host 
cells where they may be wedged apart considerably. These 
swollen ends of the hyphae (Fig. 1'3) are multinucleated, each 
one containing 10-15 nuclei. 
