150 NYLANDER ON THE ALGO-LICHEN HYPOTHESIS, &C. 



case is proved in fruticulose thalli, which, immersed in water by the 

 gomplius (that is, which are affixed very solidly to the substratum 

 by means of a conglutinating hypothallus), or at the lower part, 

 are by no means penetrated by this upwards ; whence it is abundantly 

 shown that the entrance to the nourishing moistures by no means 

 lies open from the substratum. On the contrary, it is everywhere 

 seen that immediately the thallus externally (or on the surface 

 looking towards the light) is moistened it promptly imbibes water, 

 and at once becomes vegetous. Thus, for example, Usnea sub- 

 mersed at the base of the thallus remains dry (except only the very 

 part which is submersed), but should water be sprinkled over it it 

 very greedily absorbs it, and presently softens and revives. This 

 experiment may be regarded as more than sufficient to demonstrate 

 that the atmosphere directly, by means of rain-water (from the 

 clouds or dew, &c), transfers nourishing matter to Lichens, and that 

 these can scarcely enter into their texture from the substratum, 

 unless sometimes in crustaceous thalli (received as if mechanically, 

 and not -as the result of nutrition properly so called), e. g , iron and 

 lime, which in solution are drunk up, and remain in drying, whence 

 the ferrose and calcareous states of Lichens derive their origin.* 

 Besides this, the active life, having its seat chiefly around the 

 gonidia, and putting forth young parts (lobes, laciniaB, branchlets, 

 isidia), and being manifested in the vital function of the apothecia 

 and the spermogones, it is apparent also that in these superficial 

 parts the nourishing humours necessary for all the actions of life 

 are especially and directly poured upon them. For this reason, we 

 see that the thai line surface delights in an anatomical texture which 

 assists such absorption, and that similarly the apothecia and the 

 spermogones are observed well filled with a very hygroscopic 

 lichenine gelatine, and draw to themselves water, the primary con- 

 dition of life, and receive nourishment through the medium of 

 water from the clouds, from rain, from fountains or rivers, or even 

 (in the case of maritime Lichens) from the sea.f 



Moreover, in p. 6, it is observed — " Silicicole Lichens, which occur 

 exceptionally upon calcareous rocks of sufficient hardness, but 

 never upon organic substrata. For example, Lecanora gibbosa, 

 Lecidea geographica, Lecidea contigua, &c." This does not seem quite 

 consistent with the words of the author in the same page — " The 

 attentive observation which during several years I have been able 

 to make of a great many of these vegetables in the most varied 

 conditions of existence," for it is very evident, and has been pub- 

 lished over and over again in Lichenological literature, that these, 

 in addition to many other silicicolous ones, occur also upon dead 

 bark or old w r ood. That " never," therefore, is to be deleted. Nor 



* In primary limestone neither calcareous states nor calcivorous apothecia 

 scarcely occur. 



f In a note by the author in my copy, he says— " In the Collemacei, in which 

 the entire thallus is perfused with lichenine (or Lichen gelatine), all its parts are 

 observed to be very hygroscopic. 



