132 W. ARCHER. 



not produce chlorophyll. The Protococcus-ceWs remained 

 as they Avere and did not produce filaments. 



In another series of experiments I placed spores of 

 Biutora muscorum on a corticolous form of Protococcus a 

 little larger than the preceding. The results were the same. 

 Unfortunately, I have not been able to conduct these germi- 

 nations on to the production of a thallus. The excess of 

 moisture and the development of a Mucedine destroyed the 

 young plants at the end of some loeeks. 



My own culture experiments were conducted in two dif- 

 ferent ways. In one I sowed the lichen spores with Cys- 

 tococcus upon the substratum, whereon the species are 

 mostly found, in the hope of obtaining a young lichen-thallus, 

 as Reess succeeded in doing for Collema glaucescens in his 

 " culture in the mass." In the other the spores were 

 brought along with Cystococcus on slides, and tried under 

 different circumstances, in order to make the spores germi- 

 nate, for the purpose of seeing if the germinating filaments, 

 on coming into contact with the Cystococcus individuals, 

 would wholly or partially include them, and thus, as 

 readily perceptible, demonstrate the beginning of lichen - 

 formation. 



Culture experiments in the mass (" Kultuurproeven in het 

 groot"). — These cultures had for their object the production 

 of a young perfect lichen-thallus, and by this means to 

 become acquainted at the same time with the processes 

 whereby this production takes place in nature. The sub- 

 strata whereon the spores and algse were sown were con- 

 stantly those whereon the lichens I was trying to cause to 

 originate mostly occur. 



I last year went to work in the following manner : 

 Xanthoria-s\toxe& were sown with Cystococcus (1) on 

 willow-bark, (2) on pieces of tile, (3) on very fine tile-dust 

 (obtained by hammering), and pressed as firmly as possible 

 in little saucers. This last substratum was chosen as admit- 

 ting better than the pieces of tile, after the culture, of micro- 

 scopical examination of the results. 



Lecanora spores were sown with Cystococcus (1) on 

 willow-bark and apple-bark, (2) on pieces of stone, (3) on 

 stone- dust, the last for the same purpose as in the Xanthoria 

 cultures. 



Ramalina spores finally were sown with Cystococcus on 

 oak-bark. 



Shortly before use the substances serving as substratum 

 for the culture were immersed in boiling water ; in by far 

 the greater number of cases these were, before the sowing, 



