LICHEN GONIDIA 



29 



cultures of the mature spores with these bodies, he was able to observe not 

 only the germination of the spores and the attachment of the filaments to 

 the gonidia (Fig. 6), but also the gradual building up of a complete lichen 

 thallus to the formation of perithecia and spores. 



Some years later Bonnier 1 made an interesting series of synthetic cultures 

 between the spores of lichens germinated in carefully sterilized conditions, 

 and algae taken from the open (Figs. 7 and 8). Separate control cultures of 



Fig. 7. Germination of spore of P/iyscia parietina De Not. in 

 contact with Protococcus viridis Ag. x 950 (after Bornet). 





\o 



Fig. 8. Physcia parietina De Not. Vertical section of thallus 

 obtained by synthetic culture x 130 (after Bonnier). 



spores and algae were carried on at the same time, with the result that in 

 one case lichen hyphae alone, in the other algae were produced. The various 

 lichen spores with which he experimented were sown in association with the 

 following algae: 



(i) PROTOCOCCUS. 



Pure synthetic cultures of Physcia (Xanthorid) parietina were begun in 

 August 1884 on fragments of bark. In October 1886 the thallus was several 

 centimetres in diameter, and some of the lobes were fruited. 



Physcia stellaris was also grown on bark ; in one case both thallus and 

 apothecia were deVeloped. 



' ! Bonnier 1886 and 1889. 



