2l8 
STRUCTURE AND LIFE HISTORIES 
early stages of development the sporophyte ceases to grow 
at the apex, and elongates only by the formation and 
enlargement of new cells just above the foot (intercalary 
growth). Around the base of the sporophyte there 
develops from the tissue of the gametophyte a sheath, 
but, in contrast with the mosses, no seta is formed. The 
appearance of the sporophytes, 
as they appear in clusters, has 
been aptly likened to tufts of 
delicate blades of grass (Fig. 
156). Spores are formed from 
the cylindrical archesporium, 
between outer and inner layers 
of sterile tissue. The inner 
thread-like layer is the colu- 
mella (Fig. 156). Chlorophyll 
develops in the sterile cells, and 
intercellular spaces open to the 
surface through true stomata 
(Fig. 1 66). The sporophyte, 
therefore, has the function of 
photosynthesis, and if only a 
root, or roots, would develop 
from the basal portion, it could 
well become established as an 
independent plant. As it is, it can live only as long as 
the gametophyte remains active, so as to maintain the 
supply of water to the sporophyte. The columella serves 
to conduct water up the sporophyte. 
199. Formation of Spores. As in the mosses and 
ferns, spores arise from spore-mother-cells by reducing 
divisions (tetrad-formation). In Anthoceros they do 
FIG. 164. Bryopteris fili- 
cina, showing long shoots and 
short shoots. The stolons at 
the base, with reduced leaves, 
serve not only in vegetative 
propagation, but also to anchor 
the plant. (After Goebel.) 
