BERNT LYNGE. M.-N. Kl. 



dates on this point have not been published, but every lichenologist has 

 seen fertile Xanthoria on twigs of Picea excelsa, only a few years old, and 

 Physcia virella and Xanthoria parietina are among the species which 

 first cover the stems of many deciduous trees (Fraxinus and Populus). 

 We also know BONNIER'S 1 cultures of Lichens; he succeeded in obtaining 

 fertile Xanthoria parietina and Physcia stellaris after 2 3 years. 



It is not probable that these Lichens grow so quickly on account of 

 rich nutriment. Many other Lichens perish under the same conditions, the 

 ample supply of Nitrogen being directly poisonous to them. Other Lichens 

 are not injured, but are unable to profit by it. We must assume that 

 the quick growth of these Lichens is due to innate qualities, but a quick 

 growth is not possible without sufficient food. 



The excrement of birds also contain Phosphorus. I have seen no 

 investigations of the relative importance of Phosphorus and Nitrogen to 

 coprophilous Lichens. 



We do not know much of the change of matter of the Lichens, but 

 it is probable that some related substances are built up by nitrophilous 

 Lichens. On the whole, Lichens are not much subject to attack by insects, 

 but some genera and species are difficult of preservation. If not well 

 disinfected there is little hope of preserving Rinodina balanina intact, 

 and further, many Caloplaca-species (Gasparrinia) , Xanthoria, especially 

 X. lychnea, certain Physcia and Anaptychia are difficult. We must accor- 

 dingly infer, that these nitrophilous or even coprophilous Lichens contain 

 some substance which the herbarium insects can utilise; it is not unjusti- 

 fiable to place this fact in relation to their similar nourishment. 



A fuller investigation of the change of matter of the Lichens is much 

 desired, but difficult on account of the slow course of their processes of 

 life. It is possible that the Buellieae (sensu latiore) with their relatively 

 quick growth, would offer the best material for such investigations. 



The so-called cortex is the most interesting feature of the anatomy 

 of the Physciaceae. In Anaptychia the lower cortex is usually only deve- 

 loped near the margin of the laciniae, and wanting along the median line. 

 In Physcia it is developed over the whole lower side, in some species well 

 set off from the medulla, in others gradually transformed into it. The 

 hyphae are more or less parallel to the surface, only in exceptional cases 

 apparently cellular. 



In Physcia the hyphae of the upper cortex have a different 

 texture in the various species, but usually they are more or less per- 



1 BONNIER: Recherches sur la synthese des lichens (1889), p. 19. 



