LICHEN GONIDIA 31 



supplying the germinating spores with the necessary algae. They come to 

 lie in vertical rows between the asci and, owing to pressure, assume an 

 elongate form' (Figs. 5 and 6). They have been seen in very few lichens, in 

 Endocarpon and Staurothele, both rather small genera of Pyrenolichens,and,BO 

 far as is known, in two Discolichens, Lecidea phylliscocarpa and L.phyllocaris, 

 the latter recorded from Brazil by Wainio^ and, on account of the inclusion 

 of gonidia in the hymenium, placed by him in a section, Gonothecium. 



I. Nature of Association between Alga and Fungus 



a. Consortium and Symbiosis. These cultures had established con- 

 vincingly the composite nature of the lichen thallus, and Schwendener's 

 opinion, that the relationship between the two organisms was some 

 varying degree of parasitism, was at first unhesitatingly accepted by most 

 botanists. Reinke' was the first to point out the insufficiency of this view 

 to explain the long continued healthy life of both constituents, a condition 

 so different from all known instances of the disturbing or fatal parasitism of 

 one individual on another. He recognized in the association a state of 

 mutual growth and intferdependence, that had resulted in the production 

 of an entirely new type of plant, and he suggested Consortium, as a truer 

 description of the connection between the fungus and the alga. This term 

 had originally been coined by his friend Grisebach in a paper" describing 

 the presence of actively growing Nostoc algae in healthy Gunnera stems ; 

 and Reinke compared that apparently harmless association with the similar 

 phenomenon in the lichen thallus. The comparison was emphasized by him 

 in a later paper'' on the same subject, in which he ascribes to each "consort" 

 its function in the composite plant, and declares that if such a mutual life 

 of Alga and Ascomycete is to be regarded as one of parasitism, it must be 

 considered as reciprocal parasitism; and he insists that "much more 

 appropriate for this form of organic life is the conception and title of Con- 

 sortium'' In a special work on lichens, Reinke'* further elaborated his theory 

 of the physiological activity and mutual service of the two organisms forming 

 the consortium. 



Frank" suggested the term Homobiuin as appropriate, but it is faulty 

 inasmuch as it expresses a relation.ship of complete interdependence, and 

 it has been proved that the fungus partly, and the alga entirely, have the 

 power of free grovfth. 



A wider currency was given to this view of a mutually advantageous 

 growth by de Bary '. He followed Reinke in refusing to accept as satisfactory 

 the theory of simple parasitism, and adduced the evident healthy life of the 

 algal cells — the alleged victims of the fungus— as incompatible with the 



' See p. 62. ^ Wainio 1890, i, p. 29. '■' Reinke 1872, p. 108. 



^ Reinke 1873^ ■'' Reinke 18732, p. 98. " Frank 1876. ' de Bary 1879. 



