iqiqI current literature 97 



Gonidia of lichens. — In 1905 Elfving, of the University of Helsingsfors, 

 published his studies, which he thought disproved the recent view that the 

 chlorophyllous elements associated with lichens are algae. He continued his 

 work and published his results in 1913. In the interval Danilov* began 

 s-tudies which disproved Elfving's conclusions. Danilov's results were 

 published in Russian in 1910 and in English in 1918.' Elfvixg's conclusion 

 was that the lichen hyphae threw out spherical cells, at first colorless, but later 

 colored and very similar to algae. These he supposed became separated from 

 the hyphae and divided rapidly within the lichen thallus, forming, according to 

 his results, the "gonidia" of lichens. Reviewing these results, Danilov found 

 on careful study that unstained preparations often left the impression that the 

 algal cells might really be outgrowths of the lichen hyphae, with which they are 

 intimately associated. By the use of stains, however, he was able to trace the 

 entrance of the hyphae into the algal cells, thus proving that there is no genetic 

 relationship, but that the relationship is rather that of host and parasite. The 

 "pale gonidia" of ELFV^NG were found to be dead algae which had been killed 

 by the parasitic lichen, and Daxilov was able to see distinctly the lichen hyphae 

 within them. 



Important and quite apart from the refutation of the once generally 

 accepted view of the origin of the chlorophyllous "gonidia" from the non- 

 chlorophyllous lichens, are the conclusions of Danilov regarding the re- 

 lation of the lichen to its algal host. He admits that there may be osmotic 

 filtration of certain materials from the alga to the lichen, and the like passage of 

 others from the lichen to the alga. However this may be, Danilov finds the 

 final result to be the absorption of the algae by the lichen hyphae, which enter 

 the algal cells and form dense networks of slender, thin-walled or naked absorb- 

 ing threads. Although the lichen thaUus with its prepared peptones and cer- 

 tain other organic materials is probably a favorable substratum for the algae, 

 yet the lichen is parasitic on the algae, which are killed in large numbers as a 

 result of the parasitism. On the whole the algae thrive better outside the 

 association with the lichen, while the lichen does poorly or dies outright outside 

 the association. — Bruce Fink. 



Sex organs of Phytophthora. — ^In 1913 Pethybridge,* studying a disease 

 of the potato produced by a phycomycetous fungus which he named Phytoph- 

 thora erythroseptica, observed that on the formation of the sexual organs of this 



* D.A.NILOV, A. N., tJber das gegenseitige Verhaltnis zwischen den Gonidien und 

 dam Pilzkomponten der Flechtensymbiose. Bull. Jard. Imp. Bot. St. Petersb. 10:33- 

 70. ph. 3. figs. g. 1910. 



" , The relation between the gonidia and the hy-phae in lichens. Jour. 



Botany 56:169-181. 1918. 



* PETHYBRrocE, G. H., On the rotting of potato tubers by a new species of 

 Phytophthora having a method of sexual reproduction hitherto undescribed. Sci. 

 Proc. Royal Dublin Soc. 13:529-565. pis. j. 1913. 



