18 



THE MISTLETOE PEST IN THE SOUTHWEST. 



spread of nearly 3 feet and to be more than an inch in diameter 

 just above the buttressed point of attachment to the slender branch 

 of the host (PL II, fig. 1). The rate of growth varies with the 

 host, being much slower in the cases of the mesquite and the osage 

 orange. The location of the host with respect to moist or dry soils 

 naturally also affects the rate of growth of the parasite. 



LONGEVITY. 



The parts of mistletoe embedded in the tissues of its host appear 

 to have no fixed limit to continued existence except the death of 

 its host. Specific data in this connection are not at hand for the 



Fig. 6.— A branch of an Osage orange tree infected with mistletoe, showing deformity and multiplication 

 of branches at the point of infection. 



American mistletoe, but in the case of European mistletoe Tubeuf 

 states that often sinkers are found extending through sixty to 

 seventy annual rings of growth. There are many cases in Texas 

 where mistletoe has been repeatedly broken from large branches 

 during the past twenty or twenty-five years. In cases where the 

 trunk of the mesquite and the hackberry are notably deformed it is 

 probable that the infection is nearly as old as the host. 



With regard to the aerial part it would appear that any single 

 bush would scarcely survive more than eight or ten years, chiefly 

 because of the likelihood of its being broken off by storms, or being 



166 



