XII. LICHENES. 947 



Lichen. If it had occurred to me to ascertain whether it was present, I should not have described Ascro- 

 scyphus as a Fungus; I should have recognized it as a Lichen. You will be forced to regard the gonidia as 

 peculiar to Lichens; they play too important a part to be overlooked; their nearly constant presence, their 

 form and green colour certainly demand that they should not be passed over in silence. What is their part 

 in the economy of Lichens ? Are they of no use in the respiration of these vegetables, in the formation 

 of the colouring principles which they yield, and in the power of reproducing Lichens ? Their bursting 

 through the epidermis in the form of soridia, the change of colour which they sometimes undergo in 

 contact with the air, are so many points which demand attention ; we have nothing similar in the 

 thecasporal Fungi. The thallus of Lichens is very hygrometric, as long as it is alive ; it dilates or contracts 

 according to the degree of moisture, and becomes green again ; but if it be moistened after it is dead, it 

 changes colour on almost every occasion. It is probably owing to this hygrometric action, which is par- 

 ticularly exercised at night, that Lichens remain alive iu countries where the drought is uninterrupted, 

 or where they have taken root on hard stones impermeable to water, or on iron, or glass, as you saw 

 with me in the crypt of the church at Jouarre. The thallus of Lichens is never viscous, which is very 

 commonly the case in true Fungi ; but I ought to say that I have seen very few viscous Ascophorece (Geo- 

 glussum viscosum, glui.inosuni). Lichens, especially those with a crustaceous thallus, or which grow upon 

 stones, have a strong tendency to become coloured if the stones contain oxide of iron or manganese; they then 

 acquire a ferruginous tint, which has led to many bad species having been made. The thecasporal 

 Fungi develop nearly everywhere, in damp or dark places. Lichens like plenty of light, and appear 

 indifferent as to what they grow on: the theoasporal Fungi are more particular; they especially like 

 wood, they live parasitically on insects, on Fungi, on ergoted Rye : hence habitat, without being a cha- 

 racter, is of some importance. Lichens draw their nourishment from the air, from the dew, as the 

 Lecanora of Pallas proves indubitably. 



'Nylander indicates as the characters of Lichens the colouring of blue or red by iodine; the 

 presence of oxalate of lime, of discoid or lenticular starch-grains, and of gonidia, which are often 

 absent. The colouring blue or red is to me a phenomenon more curious than characteristic. As the 

 thallus of Lichens contains starch, and Fungi never, this blueness readily distinguishes the thallus of a 

 Lichen ; but with regard to the parts of fructification, we see in Lichens, as in Fungi, that the influence of 

 the iodine is shown, sometimes on the inner substance of the conceptacle, sometimes at the extremity 

 of the paraphyses, sometimes on all the thecse, or only on their extremity. The spores also sometimes 

 exhibit it. The presence of oxalate of lime in Lichens may be of importance; but as you tell me it exists 

 also in Fungi, the latter must have been very superficially examined for it not to have been met with. 

 Clavants especially possess a large quantity. 



' One word on the Lichens and Fungi which live parasitically on the thallus of Lichens. These pro- 

 ductions have neither mycelium nor thallus. Tulasne considers them as Lichens, probably because they 

 become blue with iodine ; others think them Fungi, because they have no thallus, flow shall we 

 reconcile these views ? It is true we find gonidia, but these belong to the thallus of the Lichen on which 

 they live. 



' Now we must open another chapter, that of spermogonia, or rather of spermatogonia. I do not 

 require you to adopt this name, because a conceptacle, whether masculine or feminine, is always a 

 conceptacle. In the same way as we say /lores masculi, fares focminei, we may say conceptacidum tnascu- 

 linum, and fceminettm. 1 think, however, that you may adopt the name of spermatia (although they are 

 not found on all Lichens, and although botanists persist in considering them as parasitic Fungi), because 

 they appear to play a very real part in the economy of Lichens, and because in a complete description they 

 must be noticed; but I should wish a mark of interrogation (?) to accompany conceptaculum masctilinum. 



1 1 would also advise you to use the word thecce preferably to asci (ascosporeai). Fries, the summus 

 mayister, has said somewhere that he would never use the word theca, but always asci. See how 

 easy it is to express oneself when the following adjectives are added to these words : asci, ascelli, ascidii 



either conditions of Nostochineous or Chroococcous parallelism. Archor considers that the hypothesis of 

 Algae modified by the parasitism of ascomycetous Fungi, Schwendenor is confuted by the fact that the assumed 

 or that their immature states have hitherto been con- parasitic Fungus does not destroy, or live upon, its as- 

 founded with Algal forms belonging to these groups. sumed Algal host. En. 

 Thwaites indeed, many years ago, pointed out their 



