284 Journal of Agricultural Research vol. VI.NO.S 



as 100 pounds and measure 5 or 6 feet in diameter. The branch sup- 

 porting it will hang vertically, the broom swaying in the wind like a 

 great bag (PI. XXXII, fig. 3). The average size of the brooms is about 

 2 feet in diameter. Although a few isolated cases had been noted on the 

 seeming association of this needle fungus with these compact brooms, 

 it was not until the field season of 1913 that this association was found 

 to be of common occurrence. This was all the more interesting from 

 the fact that the cause of these formations has been a standing question 

 with all who have seen them. In some cases they have been attributed 

 to the yellow-pine mistletoe, Raz<yimojskya campylopoda (Kngelm.) 

 Piper, an error, however, not likely to be made by anyone familiar with 

 the type of broom caused by this mistletoe. 



The distribution of the brooms is quite general through the range of 

 the yellow pine in the Northwest. They are particularly abundant in 

 the vicinity of the great lakes of Idaho and in the dry valleys of southern 

 and western Montana. Climatic variation does not seem to influence 

 their distribution. 



In order to determine the cause and nature of the formation of these 

 brooms and the relation, if any, between them and the fungus common 

 on their needles, the subject has been under investigation in the field 

 and laboratory. A number of interesting observations have been 

 recorded. 



The disease caused by H. deformans primarily affects the needles. 

 In young pines the disease occurs quite generally at first, unaccom- 

 panied by any kind of hypertrophy of the shoots. Later the repeated 

 destruction of the last-formed and older needles initiates a swell- 

 ing of that portion of the branch. Sometimes the entire shoot suc- 

 cumbs to the attack in seedlings of tender years, especially the weaker 

 individuals, caused, no doubt, by the rapid drying out of the shoot. In 

 growths of 7 to i o years the fungus confined itself to the needles of the 

 season, with the result that on the infection of these a second crop some- 

 times appears about the terminal bud, which may or may not become 

 infected but may remain in a stunted, deformed condition. They help, 

 however, to maintain the shoot in a living condition. In a far greater 

 measure than in any other member of the order the mycelium of . H. 

 deformans penetrates the leaf sheath and eventually perennates in the 

 tissues of the shoot, causing a marked enlargement of the parts infected. 

 The fungus, however, fruits only on the needles. 



An additional result of the infection of the terminal shoots and the 

 continued production of food materials by the older, uninfected needles 

 is the stimulation of all lateral and adventitious buds either between 

 the primary terminal buds or at the last two or three nodes. Eventually, 

 the food materials are more and more diverted from the main shoot, 

 resulting in a gnarled and curved bunch of short branches. Young trees 



