Methods.-Callus cultures of Lycopodium used in these studies were initiated
from spores by Freeberg and Wetmore in connection with their work on cultured
gametophytes23 and have been grown for more than 7 years, with frequent subculturing,
on an agar-hardened medium consisting of Moore's mineral solution,
4 per cent sucrose, and 10 per cent autoclaved coconut milk. Stock cultures were
grown in a temperature-controlled room (25 + 20C) and received 12 hr of illumination
daily (ca. 250 ft-c) supplied by a combination of fluorescent and incandescent
lamps. Under these conditions the callus grew slowly in the form of hardened masses
of undifferentiated parenchyma cells which were light green in color. During this
extended period of culture, no evidence of organization of buds or roots ever was
observed.