36 BULLETIN 272, L T . S. DEPAETMENT OF AGEICULTTJEE. 



but requires a good degree of overhead light for normal growth. 

 Under moderate shading it 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, in the 

 scale of tolerance. It appears to thrive with less light than tupelo 

 gum, cottonwood, honey locust, red gum, ash, and willow, but requires 

 more light than red maple, oaks, elm, haekberry, 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 u pond" cypress, is less tolerant of shade than 

 the broader, two-ranked or regular form of cj^press. 



SUSCEPTIBILITY TO INJURY. 



In comparison with the important southern pines and hardwoods 

 cypress ranks high in resistance to injury. The thin bark offers 

 slight protection against fires, but these rarely occur in cypress 

 stands except along the narrow margins of the deep swamps and 

 over the shallow ponds. At intervals of 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. 



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 

 gradually increase in size and force, resulting eventually hi 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, 1 and pointed out the 

 striking similarity of the disease to the peculiar honeycomb rot in 

 incense cedar (Libocedrus decurrens Torr.), a species of the Pacific 



i Von Schrenk, Hermann, Missouri Botanical Gardens, 11th Annual Report, 1900, pp. 23-77. 



