102 



THE AMEEICAN MONTHLY 



[June, 



Flechten-thallus, and more particu- 

 larly in a subsequent article, Die 

 Algen-typen der Flechten Gonidia, 

 rightly affirms that the actual devel- 

 opment of a gonidium from the termi- 

 nal cell of a hvpha had not. with cer- 

 tainty, been observed, but only as- 

 sumed by authors. Accordingly, 

 he proposed an entirely new theory 

 on the subject, which has since at- 

 tained a wide notoriety as the Schwen- 

 denerian hypothesis. This, stated in 

 his own words, is as follows : 'As the 

 result of my researches, all these 

 growths are not simple plants, not 

 individuals in the visual sense of the 

 term ; they are leather colonies, which 

 consist of hundreds and thousands of 

 individuals, of which, however, only 

 one acts as master, while the others, 

 in perpetual captivity, provide nour- 

 ishment for themselves and their 

 master. This master is a fungus of 

 the order Ascomycetes, a parasite 

 which is accustomed to Jive on the 

 woi'k of others. Its slaves are green 

 algals, which it has sought out, or, 

 indeed, caught hold of, and forced 

 into its service. It surrounds them, 

 as a spider does its prey, with a 

 fibrous net of narrow meshes, which 

 is gradually converted into an im- 

 penetrable covering, while, however, 

 the spider sucks its prey, and leaves 

 it lying dead the fungus incites the 

 algte taken in its web to more rapid 

 activity, nay, to more vigorous 

 growth.' 



The gonidia then are unicellular or 

 filamentose algce, and the thallus is 

 a parasitic fungus. Following out 

 this idea Schwendener divided the 

 various algal types, which he re- 

 garded as constituting the gonidia, 

 into two groups, viz : — the Phyco- 

 chromace^e and the Chlorophyllaceae 

 according to the color of their re- 

 spective cell-contents. To the for- 

 mer group, that \vith bluish-green 

 cells, he assigned five algal types : — 

 I. Sirosiphonete ; 3. Rivularieaj ; 3. 

 ScytonemetE ; 4. Nostochaceffi ; 5. 

 Chroococcacete ; and to the latter 

 group three algal types : 6. Confer- 



vaceag ; 7. Chroolepidete ; 8. Pal- 

 mellaceas. 



As might be expected, such a rad- 

 ical change as this from preconceived 

 notions, gave immediate rise to ex- 

 tensive discussion and criticism, and 

 Sch^vendener was called upon to de- 

 fend his theory. This he did in dis- 

 sertations pviblished in 1872 and 1873, 

 without, however, adducing any abso- 

 lutely new arguments. 



Among the many supporters which 

 this hypothesis secured, perhaps the 

 ablest was Dr. E. Bornet, of France. 

 Adopting the two algal types of 

 Schwendener, he passed in review 

 an extensive series of lichens and 

 traced out in them the resemblance 

 between their gonidia and many 

 well-knewn species of alg^e. Of 

 these algie he concluded that a com- 

 paratively small number of species 

 furnish the gonidia for a great many 

 different species, and even genera of 

 lichens. The union between the 

 hyphie and these algae he admitted 

 to be difficvilt of demonstration, yet 

 he was able to detect it in several in- 

 stances in some of the higher lichens. 



As the result of this investigation 

 he considered himself safe in laving 

 down the following propositions : — 

 ' I . Everv gonidium of a lichen may 

 be refen-ed to a species of algse. 3. 

 The connection of the hyphre w^ith 

 the gonidia is of such a nature as to 

 exclude all possibility of the one or- 

 gan being produced by the other, and 

 the theory of parasitism alone can 

 explain it satisfactorily.' 



Without dwelling further upon 

 these theoretical views, we may turn 

 to a phase of the ^question whicli 

 would seemingly present itself to 

 every one, that of experimental dem- 

 onstration. If a lichen is a dual 

 organism, then, by sowing certain 

 lichen spores in the vicinity of cer- 

 tain algals, and imitating as nearly as 

 possible the conditions of nature, we 

 ought to be able to observe the pro- 

 cess of union. We ought to see this 

 ascomycetous fungus grasp in its re- 

 lentless web some unfortunate algal 



