16 PROCEEDINGS OP THE AMERICAN ACADEMY 



gonidia is held by Schwendener, and expressed by him even more 

 explicitly. " The green cells or gonidia," he says, " are, as is -vvell 

 known, lateral buds of the hyphiE, and as such are to be compared 

 with branches. But whereas the branches, by repeated cell-division in 

 one direction, lengthen without limit, in the development of the go- 

 nidia there occurs as a rule but one division of the primary cell to form 

 one basal and one apical cell. The latter becomes spherical, while 

 the former undergoes no change, and forms a longer or shorter stalk- 

 cell." * 



The continuation of Schwendener's investigations on the lichen- 

 thallus, in 1863, indicates no change of view, and he reiterates the 

 opinion formerly expressed by him, that " in all cases the gonidia arise 

 as lateral outgrowths of the hyphas, appearing therefore as spherical, 

 green, apical cells of short, lateral, two-celled branches." f It is not 

 until the publication, in 1868, of the concluding part of Schwendener's 

 investigations, that the views already hinted at by De Bary with regard 

 to the gelatinous lichens, are brought forward with much prominence, 

 and the views held previously are seriously questioned. Speaking of 

 the recently implied parasitic relationship between certain unicellular 

 alg£e and investing fungus-hyphce to form a compound organism known 

 as a lichen, Schwendener says : " Since the possibility of such a con- 

 dition, and in some cases its probability, is no longer a matter of 

 doubt, the question arises whether all lichens do not arise in the same 

 manner." t 



Finally, in the following year, the same observer, § breaking free 

 from all tradition and preconceived ideas, boldly states his conclusion, 

 based on new and more careful research, that lichens, so far from 

 forming a group of autonomous organisms, are simply fungi parasitic 

 upon algae ; that there exists no form of genetic connection between 

 the two elements of the thallus ; and that the compound organisms 

 known as lichens, resulting from this peculiar condition of parasitism, 

 are characterized by a form of fructification and development similar 

 to that seen in many of the ascomycetous fungi. The bitter opposi- 

 tion which this assertion at once excited on the part of lichenologists 

 was met by supporting arguments quite as vehement, but it is unne- 

 cessary to follow this discussion in detail here. It has been most ably 



* Schwendener, Untersuchungen iiber den Flechtenthallus. Nageli's Beitrage, 

 Heft II. p. 125. 



t Ibid., Heft III. p. 133. 



t Ibid., Heft IV. p. 195. 



§ Schwendener, " Die Algentypen der Flechtengonidien." See also Schwen- 

 dener, " Erorterungen zur Gonidienfrage." Flora, May, 1872. 



