36 BULLETIN 272, U. S. DEPARTMENT OF AGRICULTURE. 
but requires a good degree of overhead light for normal growth. 
Under moderate shadingit makes a persistent but less rapid growth 
than in the open. Since there is no fixed scale for grading trees in 
respect to their tolerance, general classes only are used. Cypress is 
undoubtedly to be classed as moderate, or about midway, im the 
scale of tolerance. It appears to thrive with less light than tupelo 
eum, cottonwood, honey locust, red gum, ash, and willow, but requires 
more light than red maple, oaks, elm, hackberry, black gum, slash 
pine, and white cedar. Overhead light is required, but side shading 
accelerates height growth and natural pruning of limbs. In full 
stands cypress characteristically has a clean, smooth stem and small 
crown. In other words, it cleans itself readily of branches. The 
narrow-leaf form, or ‘‘pond”’ cypress, is less tolerant of shade than 
the broader, two-ranked or regular form of cypress. ! 
SUSCEPTIBILITY TO INJURY. ~ 
In comparison with the important southern pines and hardwoods 
cypress ranks high in resistance to mjury. The thin bark offers 
sheht protection against fires, but these rarely occur in cypress 
stands except along the narrow margins of the deep swamps and 
over theshallow ponds. Atimtervals oi many years dry periods occur, 
during which fire does considerable injury in the larger swamps. 
The general fire risk, however, in timber and logging is practically 
negligible. Insect attack on living trees may likewise be counted as 
of little consequence, and up to the age of 200 years, or about the 
average life of its common associates, cypress suffers only small 
injury from fungous disease. 
CAUSE OF PECKY CYPRESS. 
DINE 
The fungus causing the well-known “‘pecky,” “‘peggy,” or “‘botty”’ 
cypress is present everywhere and in varying degree, but more par- 
ticularly in virgin cypress stands during the overmature stage. It 
is found in all ages down to saplings, and occasionally infests stands 
from 75 to 150 years old. This fungus attacks only the heartwood 
of living trees, and destroys the wood in spots. The rate of growth 
and progress of infestation is very slow. The isolated disease centers 
eradually increase in size and force, resulting eventually in the 
destruction of all intervening wood and the formation of hollow 
limbs and trunk. 
The life history of this fungus eluded careful investigation and was 
for many years only partially known. Von Schrenk made detailed 
investigations of the nature of pecky cypress,' and pomted out the 
striking similarity of the disease to the peculiar honeycomb rot in 
incense cedar (Libocedrus decurrens Torr.), a species of the Pacific 
1 Von Schrenk, Hermann, Missouri Botanical Gardens, 11th Annual Report, 1900, pp. 23-77, 
