30 



BULLETIIT 360^ U. S. DEPAETMEXT OF AGEICULTUEE. 



of 1914, a large number of badh' suppressed Douglas firs on the foot- 

 hills bordering the Clark Fork (Missoula Eiver) Valley have died 

 from a combined attack of mistletoe and beetles. Most of these trees, 

 which supported scarcely a single normal branch, had the bark of 

 limbs and trunk almost entirely removed by woodpeckers in their 

 search for the beetle before the leaves were entirely dead. The few 

 uninfected Douglas firs of the same region have not been attacked by 

 the beetles. 



The branches of large mistletoe brooms on yellow pine and Doug- 

 las fir from which the parasite has entirely disappeared are very 



Fig. 27. — Seats of original mistletoe infection on two living branches (in center and at 

 left) of mistletoe brooms on yellow pine infested with bark beetles. No other part of 

 the broom or tree was attacked. Main stem of young living yellow pine (at right) 

 attacked by bark beetles at the seat of an old mistletoe infection. 



frequently found infested with bark beetles (fig. 27), while the trunk 

 and normal branches of the trees are entirelv free from attack. 



INFLUENCE OF MISTLETOE INJURY ON THE SEED PRODUCTION 



OF THE HOST. 



Germination tests of seeds of yellow pine taken from mistletoe- 

 infected trees show that the percentage of germination is consid- 

 erably lower than is the case with seeds taken from normal trees 

 (12, p. 7). Experiments conducted b}^ the writer with seeds taken 

 from cones produced on very old mistletoe brooms of Douglas fir, 

 larch, and lodgepole pine showed a germination on an average of 

 10 per cent beloAv that of seed taken from uninfected branches of 



