174 PRACTICAL FORESTRY 
the size of chestnuts on the red cedar or juniper, and 
on the cultivated quince, apple, and other allied host 
plants causes the so-called rust. 
The disease called ‘‘ damping off” is a serious 
pest caused by the action of several minute fungus 
parasites. It causes the tissues of the seedlings to 
rot close to the ground, and the little plant withers 
and dies in consequence. It is very common in nur- 
series, where it causes the death of a very large num- 
ber of seedlings. It is favored by damp soil, high 
temperature, and humid atmosphere. It may often 
be checked by sprinkling dry sand on the surface, and 
lifting the covers of the seed-beds to permit better 
circulation of air. 
There are many other parasitic plants of a higher 
order which cause considerable damage. Mistletoes 
of various kinds infest a wide variety of species 
in both temperate and tropical districts. A little 
mistletoe (Razoumofskya pusilla) causes witch- 
broom on the black spruce in Northern districts. 
The Southern mistletoe infests the black gum, 
and in the West several species are common on 
conifers. 
6. Protection against Weeds.—The control of 
weeds or undesirable plants is of as much importance 
to the forester as it is to the farmer. To permit un- 
desirable species to gain possession of the forest soil 
