

THE TREE. 517 
are particularly susceptible to drought, and ordinarily can not secure 
a foothold except under partial protection of older stands. 
MISTLETOE. 
Mistletoe, Razoumofskya robuata, is a serious menace to western 
yellow pine. In the Coconino and Tusayan National Forests there 
are large areas where over 60 per cent of the timber has been attacked. 
On some situations, particularly on the Sitgreaves Mountain, groups 
of blackjack with every tree infested are common. According to 
Dr. George G. Hedgecock, from 1 to 2 per cent of all the western yel- 
low pine is attacked. The mistletoe usually starts in the forks of 
lateral branches and spreads as the tree grows, or it may even infect 
seedlings. The seeds of the mistletoe, which are sticky, are formed in 
the summer and ripen in the fall. When the seed covering bursts 
they may be shot from 5 to 20 feet, and often adhere to the bark of 
trees, soon developing roots which penetrate the cambium. Saplings 
attacked by mistletoe are deformed. Some of their branches are 
killed outright, their height and diameter growth is stunted, and the 
seed crop is lessened. In case of severe attack no seed is produced. 
A dry climate such as that of the Southwest lessens the danger from 
attack. Sometimes when a host tree is weakened the mistletoe may 
die from lack of nourishment. 
STOCK. 
Damage to seedlings and saplings from uncontrolled sheep and 
cattle may be excessive. When the range is overstocked cattle 
trample and injure seedlings, particularly in the vicinity of water- 
ing places, while saplings are occasionally horned and the bark par- 
tially rubbed off. If grass is scarce sheep nibble small seedlings, and 
vhen close-herded, as in crossing regular driveways, trample repro- 
duction. Over extensive areas on the Coconino and Tusayan Na- 
tional Forests bands of sheep have stunted yellow pine seedlings by 
nibbling the terminal shoots. Some sheepmen claim that this was 
done chiefly by the “markers,” or goats that go with every band. 
If sheep are salted continuously near reproduction the damage to 
the young seedlings is likely to be very great. 
Goats are so destructive both to seedlings and to saplings that they. 
should be excluded from western yellow pine stands. On the Datil 
National Forest is an area where yellow pine seedlings have been com- 
pletely destroyed and saplings permanently injured by having their 
_ bark eaten from 4 to 5 feet above the ground. The value of properly 
regulated sheep and cattle grazing in securing reproduction, however, 
must be recognized, since it prevents the formation of a heavy mat of 
grass, and loosens the soil so that the seed can germinate. Grazing 
5998°—Bull. 101—11——2 
