BBHARKS OS DB. BTYLAKDER's PAPBB. • 3 



if still kept ap, can hardly continue to be considered as para- 

 sitical.* 



2°. (Nyl. 1. c, p. 58.) Eadem pagina legimut: " It has been rc- 

 peatedl) stated thai Lichens live exclusively, or almosl exclusively, 

 at the expense of the atmosphere ; but it stands for itself that the 

 rain-water which periodically impregnates them, and which serves 

 as a vehicle for very many diverse substances which a crowd of 

 accidental circumstances may have brought upon the spot, con- 

 tributes at least an equal part of their nutrition." — Unde (exclaims 

 Dr. Nylander) auctor hcecce sic exacte (et quidem proportion/bus) 

 Cognita habet? Now, if my eminent censor had read the above 

 quoted paragraph with due attention he would easily have con- 

 vinced himself that it contained no mention whatever of "exact 

 proportions ;" it merely expresses that Lichens derive a greater 

 proportion of nutriment from rain than from the naked air. And 

 the words '• it stands for itself" imply clearly enough that, in my 

 conception, those who had spoken of the atmosphere as the main 

 instrument of Lichen nutrition must necessarily have comprised 

 " rain." My very reason for insisting upon the importance of 

 rain-agency was for the purpose of making it understood that rain- 

 water and dew served likewise as vehicles for very many organic 

 and inorganic substances brought by 'accidental circumstances" 

 within the proximity of the plant subject to be impregnated by them. 



3°. (Nyl. I.e., p. 61.) Porro, p. 6, animadvertatur : " Silicicole 

 Lichens which occur exceptionally upon calcareous rocks of suffi- 

 cient hardness, but never upon organic substrata." The word 

 11 never" used in this sentence is evidently rather too strong. I 

 ought to have said, " never, or almost never." Be it however 

 remarked, that this assertion was not founded on my personal 

 experience alone, but also on that of several classical authors, 

 whose books were before me ; such, for instance, as Acharius, 

 Fries, Nylander, and others. Now, as no one of these authors 

 mentions the circumstance of Lecidea contigua, for instance, grow- 

 ing on an organic substance, I thought it not unreasonable to 

 assume that it was not to be found there. Dr. N., however, tells 

 us that it is, as well as other species mentioned by me along with 

 it.f The rarity of the fact alluded to is, however, almost tanta- 



# When Mr. N. says (1. c.) : Fieri nequit organum (gouidia) simul estcparasi- 

 tam corporis, cugus partes vitales ayit," he seems as if he thought Schwendeneriste 

 C msidered the Alga (gonidia) as living' parasitically on the substance of the 

 Lichen ; whereas they believe, I fancy, just the contrary. As regards Dr. N.'s 

 special objections to an Algo- Lichen hypothesis, I do not see that they are in any 

 way conclusive, not one of them really coming to the point. They prove undoubtedly 

 the importance of gouidia as instruments (I dare not say organs) of lichen nutri- 

 tion, but do not, I find, in any manner demonstrate that true Gouidia are not 

 Algffi. Dr. N. very correctly remarks, on the other hand, that there has been in 

 more than one instance a confusion made between genuine AJgSB and plants that 

 bear more or less resemblance to them, also with what he calls Pseudo-Alga ; all 

 which, according to his investigations, ought more appropriately to be referred to 

 the class of Lichens. 



f Lecidea yeoyraphica has, I know, been gathered once or twice in the Pyre- 

 nees, on the stem of Rhododendron ferrugi/nev/m. 



