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122 ' MORPHOLOGY
easily traced, but when they are orange-coloured, as according
they frequently are in Cladonia miniata and Cl. digitata, they
to Wainio 1
are more
readily observed, especially if the habitat be a mossy one.
In Cl. alpicola it has been found that the rooting structure is frequently
as thick as the podetium itself. If the podetium originates from the basal
portion of the squamule, the hyphae from the chondroid layer, surrounding
the hollow centre, take a downward direction and become continuous with
the rhizoid. Should the point of insertion be near the apex of the squamule,
these hyphae form a nerve within the squamule or along the under surface,
and finally also unite with the rhizoid at the base, a form of rooting charac-
teristic of Cl. cartilaginea, Cl. digitata and several other species.
Mycelium may spread from the rhizinae along the surface of the substratum
and give rise to new squamules and new tufts of podetia, a method
of reproduction that is of considerable importance in species that are
generally sterile and that form no soredia.
Many species, especially those of the section Cladina, soon lose all
connection with the substratum, there being a continual decay of the lower
part of the podetia. As apical growth may continue for centuries, the
perishing of the base is not to be wondered at.
G. HAPTERA
The presence of haptera in Cladoniae has already been alluded to. They
occur usually in the form of cilia or rhizinae 2
, but differ from the latter in
their more simple regular growth being composed of conglutinate parallel
hyphae. They arise on the edges of the squamules or of the scyphus, but
in Cl. foliacea and Cl. ceratophylla they are formed at the points of the
podetial branches (more rarely in Cl. cervicornis and Cl. gracilis). By the aid
of these rhizinose haptera the squamule or branch becomes attached to any
substance within reach. They also aid in the production of new individuals
by anchoring some fragment of the thallus to a support until it has grown
to independent existence and has produced new rhizinae or holdfasts. They
are a very prominent feature of Cl. verticillaris f. penicillata in which they
form a thick fringe on the edges of the squamules, or frequently grow out
as branched cilia from the proliferations on the margins of the scyphus.
H. MORPHOLOGY OF THE PODETIUM
In the above account, the podetia have been treated as part of the
vegetative thallus, seeing that, partly or entirely, they are assimilative and
absorptive organs. This view does not, however, take into account their
origin and development, in consideration of which Wainio 3 and later Krabbe 4
1 Wainio 1897.
2 Wainio l897) p< 9
3 Wainio I8g0i 4 Krabbe ,g 9r>