have
thickened walls, and are grown together so as to form the wall of
the cup.

The spores are filled with granular protoplasm, in which are
numerous drops of orange-yellow oil, to which is principally due
their color. As the spores grow, they finally break the overlying
epidermis, and then become rounded as the pressure from the sides is
relieved. They germinate within a few hours if placed in water,
sending out a tube, into which pass the contents of the spore
(Fig. 47, _I_).

One of the most noticeable of the rusts is the cedar rust
(_Gymnosporangium_), forming the growths known as "cedar apples,"
often met with on the red cedar. These are rounded masses, sometimes
as large as a walnut, growing upon the small twigs of the cedar
(Fig. 47, _A_). This is a morbid growth of the same nature as those
produced by the white rusts and smuts. If one of these cedar apples is
examined in the late autumn or winter, it will be found to have the
surface dotted with little elevations covered by the epidermis, and on
removing this we find masses of forming spores. These rupture the
epidermis early in the spring, and appear then as little spikes of a
rusty red color. If they are kept wet for a few hours, they enlarge
rapidly by the absorption of water, and may reach a length of four or
five centimetres, becoming gelatinous in consistence, and sometimes
almost entirely hiding the surface of the "apple." In this stage the
fungus is extremely conspicuous, and may frequently be met with after
rainy weather in the spring.

This orange jelly, as shown by the microscope, is made up of
elongated two-celled spores (teleuto spores), attached to long
gelatinous stalks (Fig. 47, _B_). They are thick-walled, and the
contents resemble those of the cluster-cup spores described above.

To study the earlier stages of germination it is best to choose
specimens in which the masses of spores have not been moistened. By
thoroughly wetting these, and keeping moist, the process of
germination may be readily followed. Many usually begin to grow
within twenty-four hours or less. Each cell of the spore sends out a
tube (Fig. 47, _C_), through an opening in the outer wall, and this
tube rapidly elongates, the spore contents passing into it, until a
short filament (basidium) is formed, which then divides into several
short cells. Each cell develops next a short, pointed process, which
swells up at the end, gr