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Related article: Family III. Isoetaceae, 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. EQUISETINE.E
(The Horsetails or Scouring Rushes)
The Equisetineae, commonly known as the Horsetails or Scouring
rushes, are perennial plants with hollow, Order Cephalexin cylindrical, jointed and
FIG. I5i.3elaginella Martensii. a, vegetative branch; b, portion of the
stem, bearing c^nes (x) ; c, longitudinal section of a cone, showing microsporangia
(mic. sp.) in the axils of microsporophylls, and megasporangia in Order Cephalexin the axils Order Cephalexin of meg-
asporophylls; d, microsporangium with microsporophyll; e, microspores; /, por-
tion of wall of sporangium, greatly magnified; g, megaspore; h, microsporangium
opened, and most of the microspores scattered; i, megasporangium, with mega-
sporophyll; k, same, opened, showing the four megaspores. (Gager.)
fluted stems, sheath-like whorls of united leaves and terminal cone-
like fructifications. Their bodies contain large amounts of silicon,
hence the name scouring rushes.
2 90 PHARMACEUTICAL BOTANY
In some varieties the fruiting cone is borne on the ordinary
stem, in others on a special stem of slightly different form. In the
latter the spores are provided with elaters, which, being hygroscopic,
coil and uncoil with increase or decrease in the amount of moisture
present, thus aiding in the ejection of spores from the sporangia.
The number of species is small and included under one genus,
Equisetum. (See fig. 158.)
The group Filicineae is the largest among the vascular cryptogams
and includes all the plants commonly known as Ferns. The main
axis of a typical fern is a creeping underground stem or rhizome
which at its various nodes bears rootlets below and fronds above.
These fronds are highly developed, each being provided with a
petiole-like portion called a stipe which is Order Cephalexin extended into a lamina
usually showing a forked venation. Some ferns possess laminae
which are lobed, each lobe being called a pinna. If a pinna be
further divided, its divisions are called pinnules. The unfolding of a
frond is circinate and it increases in length by apical growth. On
the under surface of the laminae, pinnae, or pinnules may be seen
small brown patches each of which is called a sorus, and usually
covered by a membrane called the indusium. Each sorus consists
of a number of sporangia (spore cases) developed from epidermal
cells. In some ferns the entire leaf becomes a spore-bearing organ
(sporophyll) . Most sporangia have a row of cells around the margin,
the whole being called the annulus. Each cell of the annulus has a
U-shaped thickened cell wall. Water is present within these cells and
when it evaporates it pulls the cell walls together, straightening the
ring and tearing open the weak side. The annulus then recoils and
hurls the spores out of the sporangium. Upon coming into contact
with damp earth each spore germinates, producing a green sep-
tate filament called a protonema. This later becomes a green heart-
shaped body called a prothallus. It develops on its under surface
antheridia or male organs and archegonia or female organs as well
as numerous rhizoids. Within the antheridia are developed motile
sperms, while ova are produced within the archegonia. Order Cephalexin The many
ciliate sperms Order Cephalexin escape from the antheridia of one prothallus during a
2 9 I
wet season, and, moving through the water, are drawn by a chemo-
tactic influence to the archegonia of another prothallus, pass down
the neck canals of these and fuse with the ova, fertilizing them.
The fertilized egg or oospore divides and redivides and soon becomes
differentiated into stem-bud, first leaf, root, and foot. The foot
FIG. 158. Equisetum arvense. P, sterile branch; P 1 , fertile branch with
strobilus, or cone; R, rhizome (underground); T, cross-section of cone, showing
insertion of sporophylls in a whorl; N, N 1 , sporophylls with pendant sporangia;
S, S l , S 2 , spores Order Cephalexin with coiled elaters (el). (Gager.)
obtains nourishment from the prothallus until the root grows into
the soil, when it atrophies, and the sporophyte becomes independent.
Unequal growth and division of labor continue until a highly differ-
entiated sporophyte results, the mature "fern plant."
ORDER i. FILICALES OR TRUE FERNS (HOMOSPOROUS)
Family Poly podia cea. Sporangia with annulus vertical and
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