416. 



PROTECTION AGAINST PLANTS. 



second season, they can no longer proceed except in the 

 cambium, now further outward, and therefore grow from a 

 new growing point above the old one ; this occurs at the 

 commencement of each season's growth, so that a series of 

 wedge-shaped steps are produced in the sapwood of the host. 



Fig. 205. Quercus Cerris, L., with two Loranthtis 

 (I). (a) Swellings produced by the 

 , (b) Stunted leader of the oak which 

 will eventually die. 



Fig. 206 (After Hartig). 

 Loranthtis europaetts, L. 

 (d Haustorium growing in 

 sapwood. (x) Terminal part 

 of ditto. (e) Section of 

 another haustorium. 



Places on the host where the parasite is exposed to the air 

 swell up into masses as big as a man's head, whilst the branch 

 of the host not only suffers in growth, but frequently dies. 

 The damage done is therefore greater than by the common 

 mistletoe. The seeds are carried on to the trees by birds, and 

 chiefly by the missel-thrush. The younger portions of the 

 shoots of this parasite absorb from its host water and nitro- 

 genous and mineral matter, while it partially nourishes the 

 host with carbohydrates formed by its own aerial branches. 



