Dr. Nylander on Lichens in the Luxemhourg Gardens, 245 



XXVII. — Notulce Lichenologicce, No. XXIII. 

 By the Eev. W. A. Leighton, B.A., F.L.S. 



Dr. Nylander has published, in the ^ Bulletin of the Botanical 

 Society of France' (t. xiii. pp. 364 &c.), a veiy interesting 

 account of the lichens which he collected in the garden of the 

 Luxembourg Palace at Paris. Independently of the valuable 

 lichenological information it comprises, it is an instructive 

 example of what diligent and accurate research may accom- 

 plish m a circumscribed space, and a proof that botanists need 

 not go far afield for their collections, but that treasures lie at 

 their very doors, if only their eyes and hearts will look for and 

 appreciate them. 



The paper is prefaced by some remarks which, excellent in 

 themselves, are also highly suggestive in various ways. Of 

 all plants, lichens are the most extensively diffused, living on 

 barks, woods, rocks, stones, and earth, especially when these 

 substrata are located in a pure fresh air, which is absolutely 

 essential to their nourishment and healthy development. Most 

 lichens, as a general rule, avoid towns, and if they make their 

 appearance there, are most frequently found in a state of in- 

 complete development, either sorediate or entirely sterile. 

 There are, indeed, some few species (as Fhyscia jparietina^ Ph. 

 jpulverulentaj var. pityrea^ Ph. ohscura^ Ph. stellartSj Placodmm 

 murorunij PL caUopismuniy &c.) which willingly inhabit cul- 

 tivated places ; but in the interior of great towns we may ge- 

 nerally search in vain for them on the trunks of trees and on 

 the walls. In such localities their usual abodes are occupied 

 by Cryptogams of an inferior order (such as Protococcus) j which 

 delight especially in an impure air, or one surrounded with 

 houses or walls. Lichens, on the contrary, refuse to live in 

 such conditions. The trunks of trees in the gardens and 

 plantations of great towns are for these reasons destitute of all 

 trace of lichens. On the other hand, in the open country 

 every tree is more or less adorned with thalli and apothecia of 

 divers colours. The magnificent trees of the gardens of the 

 Tuileries bear scarcely anything but Protococcus. In the 

 Jardin des Plantes scarcely any trees bear lichens, and those 

 only in the most exposed places. 



We may observe, en passant j that lichens are by no means 

 parasites, properly so called ; and it is at least very doubtful 

 whether they are injurious to the trees upon which they grow. 

 All that can be said is that they may to a certain extent be 

 injurious to the living bark, either by obstructing its respira- 

 tory fimctions or by applying to its surface an excessive 

 humidity. 



