418 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



height of certain brown parmelias growing on trees, particularly 

 birches, as these lichens are sensitive to prolonged snow cover and 

 quickly disappear from those parts of the tree covered by accumula- 

 tive or drifting snow falls. Thus it would be possible to judge not 

 only general but specific localized snow depths for estimating water- 

 shed and irrigation potentials, and probable snow falls in mountain 

 passes, and to assist in railroad engineering problems relative to the 

 location of snow sheds, and in highway maintenance and the tem- 

 porary location of snow fences. 



Injury hy lichens. — Lichen injury to valued stained-glass windows 

 of old cathedrals and to marble, alabaster, and Florentine mosaics has 

 been reported by various observers (13). The deleterious effect of 

 Parmelia tinctorum Despr. upon a Buddhist monument in central 

 Java is given by Seshadri and Subramanian ( 18a) . Chemical analysis 

 of this specimen revealed a high percentage of atranorin (20.3) ; the 

 authors suggest that this water-soluble acid is capable of causing 

 damage to calcareous substrates. E. Bachmann (13) had earlier 

 published a series of observations (1904-15) upon the action of lichens 

 on mica, garnet, quartz, and calcareous rocks indicating that the first 

 two substances were rapidly decomposed wliile calcareous rocks were 

 dissolved through the action of the lichens. The more resistant quartz 

 was minutely etched. Bachmann concluded that lichens exert a me- 

 chanical and chemical action on their substrate, and that they must 

 give out solvent acids in the process. Orchardists and silviculturists 

 have long been interested in the relationship of lichens to trees, and 

 many sprays, including Bordeaux mixture, caustic soda, and light- 

 boiling tar oils, have been recommended for the removal of these "un- 

 sightly if not injurious plants." Indirectly they may be the cause of 

 economic loss by serving as shelter for harmful insects seeking cover 

 and depositing eggs. Kaufert has noted that the bark of Populus 

 tremuloides remains permanently smooth through the presence of a 

 persistent periderm, but that if injured by fungi, lichens, or mechani- 

 cal injury the bark may be stimulated to develop rough fissures. In 

 studying the influence of Usnea species upon trees in South Africa, 

 Phillips (13) concluded that in this case the lichen is definitely detri- 

 mental in that its fungal component is parasitic upon tissue external 

 or internal to the cork cambium. Vigorous crowns as well as defective 

 ones may be infected. Since the lichen cannot develop luxuriantly 

 under the conditions obtaining in undisturbed high forests, he recom- 

 mended that the forest canopy be preserved as a means of inhibiting 

 the rampant growth of this lichen. Seshadri and Subramanian (18b) 

 present more definite evidence of lichen damage to trees. In this 

 instance it was noted that the more tender portions of sandalwood 

 trees bore heavy growths of lichens which appeared to affect the nor- 

 mal development of the tree. The principal lichen, Ramalina tay- 



