BLIGHTS OF CONIFEROUS NURSERY STOCK. 3 
occurred at nurseries in Colorado, Minnesota, Pennsylvania, and 
New York without being recognized by the nurserymen. 
HOW SUN SCORCH WORKS. 
In serious cases of sun scorch, seedlings of all ages are killed out- 
right. In less serious cases part of the plant is killed. Either the tips 
or the lower needles may be first affected. If the tips are injured, 
stem and bud may be killed as well as the needles, so that growth 
can be resumed only by lateral buds below the point of injury. In 
slight attacks only the needles, and often only the tips of the needles, 
are killed. When the lower needles are the only ones attacked, 
despite the fact that they are well protected from sun and wind in 
dense stands, it must be assumed that the younger needles at the 
tips, subjected to much more light and wind, have survived at the 
expense of the lower ones by taking more than their share of the 
available water. Affected needles first turn slightly yellowish, lose 
their green until they have become a pale straw color, and then grad- 
ually turn deeper brown until they become nearly red. In summer 
most dead needles fall within a month. 
In crowded seed beds, especially on very sandy soil, attacks may 
take place very suddenly in hot, dry weather, and patches of seed- 
lings up to a foot in diameter may be entirely killed. It is these 
definite, clean-killed patches which have most often caused the disease 
to be called parasitic. Such even death can be explained on a drought 
basis only by assuming that in such cases the root systems of all the 
seedlings involved have been equally extended in normal competition 
for water, just as the tops often grow to an exactly even height in 
competition for light, so that all the seedlings in the patch are on 
terms of equality when the competition becomes critical. When part 
of the seedlings in a crowded bed are badly suppressed the smaller 
seedlings are in some cases, when transpiration is rapid, even less 
subject to sun scorch than the larger. Since the suppressed seedlings 
presumably have less extensive root systems, their endurance in such 
cases must be explained by the fact that they are also less subject to 
water loss because of the protection afforded by the tops of the larger 
plants around them. When the beds are not crowded and the 
weather does not favor extremely rapid water loss, death does not 
occur so suddenly or in such definite patches. - 
In the cases of transplants a certain number die soon after they are 
set out and before root growth starts. This has been called “ trans- 
planting loss” and is not included under the term “sun scorch.” 
“Sun scorch ” is used in transplants for death due to excessive water 
loss after the plants have become partly established and commenced 
growth. The work of sun scorch in transplant beds at Halsey differs 
from that in seed beds in that the trouble in the transplants does not 
