352 REPORT OF THE COMMISSIONER OF AGRICULTURE. 
conditions, they give rise to germinating filaments which enter the — 
leaf through the stomata and forma mycelium in its tissues. In its 
growth this mycelium winds through the intercellular spaces (Plate 
lil, Fig. 10), and obtains sufficient food for its development by means 
of haustoria which it sends into the cells.* 
Uredo-stage.—At a definite period these mycelium threads form 
compact masses in certain places beneath the epidermis, and from 
these masses arise short, upright hyphe or basidia, each of which 
bears a single spore upon the end (Plate ITI, Fig. 10). The spores, in- 
creasing in number and size, rupture the epidermis (Fig. 10 b), and - 
when ripe escape by falling from their basidia, which, in this case, 
are known as pedicels (Fig. 10 dd). This is the summer or uredo 
pe ot the fungus, and its external appearance has been already de- 
scribed. 
The uredospores (Fig. 11) are round orovate, dark yellow, with a 
somewhat thickened wall and an echinulate surface, upon which one 
or two bright places may be seen. These bright spots are caused by 
perforations in the endospore or inner layer of the wall, and it is 
through these perforations that the young, growing hypha protrudes 
in germination (Fig. 11 a). 
Teleuto-stage.—These germ filaments bore through the epidermis* 
and form a mycelium like that developed» from the «cidiospores 
in form, manner of growth, and function. The uredospores are 
produced in this manner for several generations, but as autumn ad- 
vances spores of another character appear among them. This third 
form is also unicellular, but darker in color and thicker walled than 
either of the others. It has a smooth surface, and opposite to the 
attachment of the pedicel there is a thin place in the wall that affords 
a point of least resistance to the germinating hypha. When ripe 
these spores fall off, carrying with them the pedicels which become 
detached from the stoma beneath. The name teleutospores is ap- 
plied to this third form, and they may occur mingled with the uredo- 
spores or form independent spots. In the latter case they occur upon 
the petiole.+ The teleutospores are the resting or winter spores of 
the fungus, and, although appearing in the fall, they do not germi- 
nate until the following spring after a winter period of rest. The 
germinating tube pushes through the thin place in the wall opposite 
the point of attachment of the pedicel and forms a short branched 
hypha or promycelium. From the end of each branch small buds or 
sporidia are cut off by a special process. These are capable of germi- 
nating and producing a mycelium in the plant tissues, and this in 
turn reproduces the spermogonia and zcidia, thus completing the 
alternation of generations. 
It will be seen that the life history of this fungus is the same as 
that of other Uredinece, but it differs from the other genera of this 
group in that its winter spores are unicellular. It closely resembles 
Uromyces rumicum, found upon sorrel, but, so far as known, it has 
never been found upon any host but the Beet, and this renders the 
matter of subduing it comparatively easy. Since the teleutospores 
do not make their appearance until autumn, and as the carrying 
the fungus over winter is believed to depend upon the teleuto- 
spores the thrifty cultivator will watch for the earlier stages of the 
anaes. 
* Sorauer, Pflanzenkrankheiten. 
+ Frank, Die Krankheiten der Pflanzen. 
