270 EEV. J. M. CEOMBIE ON THE ALGO-LICHEff HYPOTHESIS. 



directly poured forth upon their surface, and penetrates the 

 cortical stratum (when this is present) till it reaches the goni- 

 dial stratum, around which the active vegetative life especially 

 has its seat. The gonidia, therefore, are not special nutritive 

 organs, although (as the instruments of absorbing carbonic acid) 

 they greatly aid in promoting the nutrition, but act rather as 

 vivifying stimulants, — the nutrition taking place through the 

 corticali-gonidial stratum, in which the cellules also play their 

 part, and Berve in the slow nutrient process which is so charac- 

 teristic of lichens. Consequently neither the poor prisoners nor 

 the tyrant master act the parts assigned to them in Schwen- 

 denerism ; and the strange parasitism which it assumes is found 

 on investigation to have no actual existence. 



The second objection, and one of even greater validity, is that 

 there are neither fungal-mycelia nor algal-colonies in the struc- 

 ture of Lichens. Indeed, were there so, we should naturally expect 

 to find Lichens most abundant in those habitats which are most 

 frequented by Fungi and Alga?, and there perceive the whole 

 process of manufacture going on before our eyes. Every field- 

 lichenist, however, is perfectly aware that he need not look for 

 lichens where these other Cryptogams have their special haunts. 

 Similarly and conversely, lichens in all stages of growth are met 

 with plentifully in situations, e. g. granitic detritus and boulders 

 towards the summits of lofty mountains, where fungal-mycelia 

 and terrestrial algals are unknown. But, notwithstanding a 

 certain superficial resemblance between the hyphae of Lichens 

 and of Fungi, their structure and character, as Nylander has 

 repeatedly shown, are entirely different. The hyphae, or rather 

 " myelohyphae," Nyl., of Lichens, are perennial, firm, with thick 

 walls, penetrated by lichenin,' imputrible, and not dissolved by 

 hydrate of potash. On the other hand, the hyphoid mycelia or 

 " protohyphse " of Fungi are caducous, very soft, with thin walls, 

 not at all amylaceous, readily putrifying on maceration, and on 

 the application of hydrate of potash immediately becoming dis- 

 solved. Moreover, the licheno-hyphae are rigid though elastic, 

 nowhere flexuose and contorted*, but straight or straio-htish, so 



* M. Stahl, in the work already referred to (Heft i., " Ueber die geschlecht- 

 liehe Fortpflanzung der Collemaceen ") represents the apothecia as originating 

 from filamentose contortions or contorted hypha:. This, however, as shown by 

 Nylander (in 'Flora,' 1859, p. G25, and 1879, p. 304), is entirely erroneous, 

 and consequently is of itself sufficient to cast great doubt npon all Stabl's other 

 observations. 



