MISCELLANEOUS PARASITIC AND SAPROPHYTIC ORGANISMS. 15 



ward to southern California. Throughout southern Ohio, Indiana, 

 Illinois, and Missouri it is found chiefly on the black gum (Nyssa 

 sylvatica Marsh.)- In the Southern States it is found on almost all 

 species of deciduous forest trees, including the sycamore (Platanus 

 occidentalis L.), elm (Ulmus americana L.), oaks (Quercus sp.), red 

 gum (Liquidambar styraciflua L.), ashes (Fraxinus sp.), cottonwood 

 (Poji/ilns deltoides Marsh.), and many others of the smaller shrubby 

 species of trees, like the mesquite (Prosopis juliflora (Swartz) DC.). 



Where it is present in any large quantity, the mistletoe is regarded 

 as a serious enemy of the trees upon which it grows. In the more or 

 less virgin forest 

 tracts of the Mis- 

 sissippi Valley, 

 extending from 

 southern Missouri 

 into Arkansas and 

 northeastern Loui- 

 siana, man} 7 tracts 

 are found which 

 are so badly in- 

 fested as to se- 

 riously interfere 

 with the annual 

 rate of wood accre- 

 tion. In the ex- 

 treme Southern 

 States vigorous ef- 

 forts arebeingmade 

 to prevent the at- 

 tack of the mistle- 

 toe, which has be- 

 come a serious 

 enemy to forest 

 and shade trees in 

 southern Louisiana 

 and Texas. The 

 parasite is distributed from tree to tree chiefly by birds, and when 

 it has once obtained a foothold in any given region, practically 

 every tree in that locality is affected by it. The parasite is a peren- 

 nial and gradually absorbs the food materials from the branch upon 

 which it is situated, and not only kills off that part of the branch 

 toward the outside of the tree from its point of attachment, but 

 also causes the formation of large swellings, or tumors, which are 

 most characteristic in the black gum. Figure 1 shows the extent to 

 which the oak may be attacked by this parasite. 



79152 Bui. 14909 2 



FIG. 1. Oak trees with mistletoe on the branches, 

 become literally covered with this pest. 



Some trees 



