Pharmaceutical botany - Lighthouse Survival Blog

66 PHARMACEUTICAL BOTANY
gonium. The base of the stalk remains imbedded in the basal portion of the archegonium
at the tip of the leafy stalk and forms a foot or absorbing process. In
growing upward the sporogonium ruptures the neck of the archegonium and carries
it upward as the covering of the capsule, or calyptra. The calyptra is thrown off
before the spores are matured within the capsule. The upper part of the capsule
becomes converted into a lid or operculum at the margin of which an annulus or
ring of cells forms. The cells of the annulus are hygroscopic and expand at maturity,
throwing off the lid and allowing the spores to escape. This completes the asexual
or sporophyte generation. The spores falling to the damp soil germinate into
protonemata, thus completing the life cycle in which is seen an alteration of genera-
tions, the two phases, gametophyte alternating with sporophyte.
DIVISION III—PTERIDOPHYTA
The most highly developed cryptogams showing a distinct alter-
nation of generations in their life history. They differ from the
Bryophytes in presenting independent, leafy, vascular, root-bearing
sporophytes.
SUBDIVISION I.—LYCOPODIALES OR CLUB MOSSES
Small perennial vascular, dichotomously branched herbs with stems
thickly covered with awl-shaped leaves. The earliest forms of vascular
plants differing from ferns in being comparatively simple in structure,
of small size, leaves sessile and usually possessing a single vein. Except
in a few instances the sporangia are borne on leaves, crowded together
and forming cones or spikes at the ends of the branches. Homosporous.
Family i. Lycopodiace^, including the single genus Lycopodium
with widely distributed species. The spores of Lycopodium clavatum
are ofEcial.
Family 2. Selaginellace^, including the single genus Selaginella,
with species for the greater part tropical. Plants similar in habit to the
Lycopodiaceas but showing heterospory.
Family 3. Isoetace^, including the single genus Isoetes whose
species are plants with short and tuberous stems giving rise to a tuft of
branching roots below and a thick rosette of long, stiff awl-shaped
leaves above. Heterosporous.
SUBDIVISION II.—EQUISETALES
(The Horsetails or Scouring Rushes)
The Fquisetales, commonly known as the Horsetails or Scouring
rushes are perennial plants with hollow, cylindrical, jointed and fluted