18709. | Microscopical Fungi Infesting our Cereals. 617 
In the same way it has been shown that other rust diseases, for 
instance, such as are produced by Uredo rubigo vera, which also 
destroys our cereal plants, are originated by certain cluster-cups 
growing on other plants in the neighborhood of corn-fields. 
If we examine the rust-pustules more closely, either by open- 
ing them with a needle or by making thin sections, we shall find 
beneath the epidermis and growing on short peduncles, numerous 
yellowish spores. They represent simple oval cells, the proto- 
plasm of which contains little drops of an orange-colored oil. 
The hyaline episporium is granulated.and shows several translu- 
cefit spots, the places from which the germ tubes will proceed. 
These germ tubes are rapidly developed, often within a few hours. 
They penetrate the stomata of other leaves and repeat the pro- 
duction, first of a mycelium, then of numerous spores, which again 
pierce with their germs through the epidermis of other plants. 
In this way the the process is continued through the course of 
summer, and it is easily explainable that under favorable circum- 
stances the disease may be propagated from field to field, over 
vast tracts of land, assuming quite an epidemic character. 
Towards the close of the hot season we see our fungi entering 
a new stage of their development. Repeated examinations of the 
rusty pustules will show that the latter are gradually transformed 
into bodies of a dark-brownish color. Let us examine these dark 
bodies a little closer. We shall find that from the former mycelium 
spores of a quite different shape and color have been produced. 
The Uredo or summer spores have disappeared and in their 
place we behold numerous dark-brownish two-celled spores with 
thick or perfectly smooth membranes growing on long pedicles. 
They are what is known as brand (Puccinia), and were formerly — 
described as an autonomous species of fungi. In reality they are 
the winter or Teleuto spores of the rust. The spores remain 
with their peduncles attached to their stroma during the winter, 
and do not begin their germination before the following spring. 
Then one or several germ tubes are formed, which at their upper 
extremities become segmented into several cells. From each of 
these cells we see growing out a very fine thread, producing a 
sporidium. These sporidia are set free and are scattered by the 
wind, and when brought on the leaves of barberry are sure to 
produce the cluster-cups first described. (The latter fact has 
again been proved by numerous direct experiments. 
