MISTLETOE. 57 



thick. In cases where incense cedar mistletoe, for in- 

 stance, has grown to a high age with its host tree, the 

 bark of the latter becomes so thick that it can not 

 be pierced by the young mistletoe sprouts. The mistle- 

 toe then lives without green parts, consisting only of 

 cortical roots and sinkers, and depending altogether for 

 all food on its host. In this state it acts very much like 

 a fungus, which also is unable to elaborate its own 

 food and has to rely upon other plants (see p. 24). 



Phoradendron rarely attacks young trees. Razou- 

 mofskya, on the other hand, very often does consid- 

 erable damage to young yellow, Jeffrey, and lodgepole 

 pine. If the stem or leader is infected, the young tree 

 is killed in the course of time, or at least prevented from 

 developing a straight, clean bole. Different species of 

 Phoradendron and Razoumofskya are confined to cer- 

 tain hosts. Phoradendron juniperinum Ubocedri, for 

 example, grows on incense cedar; Phoradendron juni- 

 perinum on junipers; Phorandendron bolleanum on 

 white fir and juniper; Phoradendron flavescens on oak 

 and other broadleaf trees; Razoumofskya campylo- 

 poda on sugar, yellow, and Jeffrey pine ; Razoumofskya 

 americana on lodgepole pine; Razoumofskya douglasii 

 on Douglas fir; and Razoumofskya occidentalis on 

 white fir. 



Our white fir is the host of both a Phoradendron and 

 a Razoumofskya. The light-seeking Phoradendron 

 botteanum lives exclusively in the very top of the older 

 trees, chiefly in the leader, and there develops the con- 

 spicuous tufts of green foliage, which even at a great 

 distance reveal the presence of the mistletoe. It finally 

 kills the leader, which is replaced by a secondary leader, 



