130 
Mycologia 
CO2 excluded. On media containing mineral salts but no organic 
matter, the alga grows, but not so well. These results square 
beautifully with those of Tobler on one of the same plants, one 
worker giving special attention to the lichen and the other con- 
fining himself to the algal host. The two researches prove that 
the alga which lives in the thallus of Xanthoria parietina (L.) 
Th. Fr. can obtain its organic matter and its mineral salts from 
the lichen. Radais (no) cultivated Pleurococcus vulgaris in 
total darkness on media containing albuminoids or hydrocarbons 
and found that it can utilize these substances as do saprophytic 
fungi and bacteria, and that it grows as rapidly and produces 
chlorophyll as well as in its ordinary habitat. The chlorophyll 
was analyzed with the spectrum and was found to be normal. 
So far as they go, these results confirm those of Treboux and 
Artari. Beijerinck (19), Bouilhac (51), Etard (51), Klebs (71) 
and others have also obtained results with algae in pure cultures, 
somewhat similar to those of Treboux and Artari. Two of these 
workers studied blue-green algae, which behave in the same 
manner as the green algae. 
Beijerinck (19) cultivated the algal host of Physcia in elm- 
bark gelatine, with malt extract added. This alga, Cystococciis 
according to his results, he thinks, is not common in his region, 
except as the host of lichens, but is replaced in free nature by 
Pleurococcus. The Cystococcus was found to have no vacuole or 
pyrenoid, though other authors seem to find both vacuoles and 
pyrenoids in algae growing in lichens. The alga produced 
zoospores in pure cultures, freed from the lichen. His results are 
valuable, but it is very doubtful whether he found an algal host of 
lichens which is not common in the free state in the same region. 
Baranetsky ( 14) cultivated thin sections of Collema pulposmn 
(Berlin.) Ach. and the portion of the algal colony contained. He 
got young Nostoc colonies, which grew rapidly, while the lichen 
died. He obtained similar results with Peltigera canina (L.) 
Hofifm. Famintzin and Baranetsky (54) isolated algae from the 
lichen parasites, and the algae produced 30 to 60 zoospores after 
the manner of free Chlorococcum humicola. They worked also 
on the hosts of Xanthoria parietina (L.) Th. Fr., Evernia fur- 
