Stahl[203] sufficiently demonstrated the importance of these gonidia in 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[204] (Figs. 5 and 6). They have been seen in very few lichens, in _Endocarpon_ and _Staurothele_, both rather small genera of Pyrenolichens, and, so far as is known, in two Discolichens, _Lecidea phylliscocarpa_ and _L. phyllocaris_, the latter recorded from Brazil by Wainio[205], 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 convincingly 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[206] 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 interdependence, 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[206] 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[207] 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 _Consortium_.” In a special work on lichens, Reinke[208] further elaborated his theory of the physiological activity and mutual service of the two organisms forming the consortium.