INJURIES INDUCED BY PLANTS 



35 



CRYPTOGAMS 

 PSEUDO-PARASITES 



Among cryptogams, also, we meet with plants which, although 

 not parasites in the narrower sense of the term, may prove 

 directly injurious to other plants by the manner of the attack 

 which they make- upon them. A case in point is furnished by 

 ThelepJiora laciniata^ whose thallus" lives on the humus con- 

 stituents in the upper 

 layers of the soil, but 

 whose sporophoresgrow 

 up and embrace young 

 plants, as is shown in 

 Fig. 8. Commencing at 

 the ground, they enve- 

 lop leaves and branches 

 so completely as to 

 smother and kill them. 

 I have found the fer- 

 ruginous, sessile, more 

 or less confluent sporo- 

 phore, with its lacerate 

 pileus,f commonest on 

 young spruces,silver firs, 



and WeymOUth pines, FlGi g. Thelephora laciniata. 



on which it ascends 



to a height of eight inches from the ground. For similar 

 reasons, though to a much less extent, trees may be injured 

 by an excessive growth of lichens. A luxuriant growth of 

 lichens on the stems and branches of trees is a sign that the 

 air is permanently humid. It is also connected, however, with 

 the quality of the soil and the rate of growth of the trees, and 



1 R. Hartig, Untersuchungen a. d.forstbot. Inst., I. p. 164. Berlin, 1880. 



* [Thallus is the term applied to the cellular vegetative body of many 

 lower plants. ED.] 



t [The pileus of a mushroom or similar fungus is the expanded upper part, 

 on a portion of whose surface the spores are produced. ED.] 



D 2 



