12 FUNGI. 



substance, or thallus of lichens, are the supposed algae ; and the 

 cellular structure which surrounds, encloses, and imprisons the 

 gonidia is the parasitic fungus, which is parasitic on something 

 infinitely smaller than itself, and which it entirely and absolutely 

 isolates from all external influences. 



Dr. Bornet believed himself to have established that every 

 gonidium of a lichen may be referred to a species of algae, and 

 that the connection between the hypha and gonidia is of such a . 

 nature as to exclude all possibility of the one organ being pro- 

 duced by the other. This he thinks is the only way in which it 

 can be accounted for that the gonidia of diverse lichens should 

 be almost identical. 



Dr. Nylander, in referring to this hypothesis of an imprisoned 

 algal,* writes : " The absurdity of such an hypothesis is evident 

 from the very consideration that it cannot be the case that an 

 organ (gonidia) should at the same time be a parasite on the 

 body of which it exercises vital functions ; for with equal 

 propriety it might be contended that the liver or the spleen 

 constitutes parasites of the mammiferse. Parasite existence is 

 autonomous, living upon a foreign body, of which nature 

 prohibits it from being at the same time an organ. This is 

 an elementary axiom of general physiology. But observation 

 directly made teaches that the green matter originally arises 

 within the primary chlorophyll- or phycochrom-bearing cellule, 

 and consequently is not intruded from any external quarter, nor 

 arises in any way from any parasitism of any kind. The cellule 

 at first is observed to be empty, and then, by the aid of secretion, 

 green matter is gradually produced in the cavity and assumes a 

 definite form. It can, therefore, be very easily and evidently 

 demonstrated that the origin of green matter in lichens is en- 

 tirely the same as in other plants." On another occasion, and in 

 another place, the same eminent lichenologist remarks,t as to 

 the supposed algoid nature of gonidia — " that such an unnatural 

 existence as they would thus pass, enclosed in a prison and 



* Nylander, "On the Algo-Lichen Hypothesis," &c, in "Grrevillea," vol. ii. 

 (1874), No. 22, p. 146. 

 t In Eegensburg "Flora," 1870, p. 92. 



