Parasitic Fungi of Illinois. 145 
the common red cedar, constituting the so-called ‘cedar balls,” 
of orange color, especially noticeable after a rain in the month 
of May. The relation of these two forms of the fungus was 
not suspected until carefully established by Oersted, a botanist 
giving special attention to such matters, and well qualified for 
such observations and experiments. The fact having been as- 
certained, a thoroughly practical remedy consists in clearing 
away the worthless red cedars, or, in case of a few of these 
trees, which for any reason are wished to be saved, picking off 
and burning the “cedar balls.” In this case the spores pro- 
duced on the apple leaves cannot germinate and grow on the 
apple, but must reach, by wind currents or otherwise, the cedar 
leaves, where alone one essential stage of development takes 
place. From the cedar the spores must again be carried to the 
apple tree, or allied host, thus alternating back and forth as a 
necessary requirement of continued existence. 
This is by no means a solitary example of known alterna- 
tions which render possible the agency of man in preventing 
plant diseases caused by these pernicious parasites; but to gain 
the fullest possible mastery we still need much investigation 
and experiment by those most competent to conduct them. It 
has long been known that the rust of wheat (Puccinia grami- 
nis) has an alternate form on the barberry bush, but since the 
rust occurs in vast regions of our country where no barberry 
exists, we know that this plant is not positively essential to the 
continuous development of the rust. It now seems probable 
that the barberry stage is a reality, and perhaps in some way 
beneficial to the Puccinia (rust), but not essential. It still re- 
mains, however, to be ascertained whether or not there is some 
other common plant usually found in or near the wheat fields, 
which takes the place of the barberry, and thus permits the 
continued growth of the rust. 
What might be the practical value of investigation in this 
direction? There are annually produced in Ilinois about 50,- 
000,000 bushels of wheat. The destruction of one-hundredth 
part of the crop by this fungus probably falls, as an estimate, 
far within the actual limits of loss as an annual average. This 
represents 500,000 bushels, which, at seventy-five cents per 
bushel, is $875,000. If it could be demonstrated that the eradi- 
