ta ae 
7 cee & 
1906] BRIEFER ARTICLES 57 
have much to do with their less thrifty appearance. However, the presence 
of Nostoc colonies on the soil does not necessarily imply the infection of 
all Anthoceros plants near them. As a matter of fact, a good many 
Anthoceros plants free from Nostoc can be found on unsterilized soil. 
These look better than those beside them containing Nostoc colonies, and 
' as well as those in the dishes of sterilized soil. 
Where cultures receive light mainly from the side, as is generally the 
case in a laboratory, Anthoceros plants, like fern-prothalli and the thalli 
of Fimbriaria, turn up from the surface of the soil, presenting their normally 
upper surface toward the window and bearing rhizoids on the shaded 
side. These plants necessarily contain fewer Nostoc colonies than those 
remaining flat on the soil, for the younger and elevated parts are less acces- 
sible to Nostoc filaments. Comparisons of older cultures than those just 
described shows that Anthoceros plants containing only one or two algal 
colonies are nearly or quite as thrifty as those with none, and are decidedly 
more vigorous than those with many. 
PRANTL‘ attributed an advantage to Anthoceros from its association 
with Nostoc, on the ground that Nostoc might fix the free nitrogen of the 
air and contribute its products to the liverwort, but the weight of evidence 
seems now to be against the assumption that blue-green algae by and of 
themselves add at all to the combined nitrogen in the soil,5 whatever the 
results of their association with N-fixing soil bacteria may be. The fact 
that, in my cultures at least, Anthoceros does better when free from Nostoc, 
removes all ground for PRANTL’s claimed advantage from the association 
so common in nature. 
On the other hand JANczEwskt’s designation of the Nostoc colonies 
as parasitic® is not logically justified by my cultures or by the luxuriance 
in growth and by the fertility of these two species of Anthoceros in this 
region in ordinarily good seasons. Last year they throve as I never saw 
them before. This season has been by no means so favorable, dry weather 
having come long before the plants, held back by the cold and dryness of 
November and December, could ripen their spores in large numbers. 
All T feel inclined to say is that Nostoc certainly does not benefit An- 
thoceros, which in fact does better without it. 
It is a matter of common observation that many blue-green algae 
+Pranti, K., Die Assimilation freien Stickstoffs und der Parasitismus von 
Nostoc. Hedwigia 28:135. 1889. 
‘ Prerrer, W., Pflanzenphysiologie, 2te Auflage, 1:386-7, 393. 1897. 
° JANCZEWsKI, A. DE, Vergleichende Untersuchungen iiber die Entwickelungsge- 
schichte des Archegoniums. Bot. Zeit. 377 f. 1872. 
