solid stems and leaves, of the concentric tj^pe. The
epidermis and stomata are scarcely to be distinguished
from those of the highest plants.
456. The typically large leaves are sometimes simple,
flat blades, but more commonly they have branched into
*' compound" blades of extraordinary complexity and
beauty of outline. The young leaves before expanding
are generally coiled or rolled, so that as they grow up
and open they unroll from below upward (i.e. cir-
cinately). Their vascular bundles (here usually called
OLD-FASHIONED FERNS 257
''veins") present different patterns, sometimes being
parallel to one another or divergent (veins ''free"), or
uniting here and there in a netted fashion (veins
"reticulated").
457. Since the sporophytes of ferns are long-lived
the}" delay the formation of their spores, this sometimes
not taking place for a few years (or many years in tree
ferns). In the more primitive ferns the spores develop
from internal cells (as in Anthoceros of the Bryophyta),
but in the higher forms they are produced in superficial
sporangia.
458. On account of the dominance of the sporophyte
its structure has been emphasized in the s^^stematic
classification of the ferns, although some consideration
has latterly been given to gametophyte characters.
About 3800 species of Ferns have been described, and
they are widely distributed throughout warm and tem-
perate regions.
459. There are two classes of Ferns, as follows:
1. Old-fashioned Ferns (Class Eusporangiatae) in which
the spores develop from internal cells.
Fig. 133. — Ophioglossuni. Fig. 134. — Angiopteria
(Marattialcs); develop-
ment of sporangia.
460. Here are the Adder-tongues (Order Opiiio-
GLOSSALEs) by many botanists regarded as the lowest of
the Ferns, and not very distantly related to Anthoceros
of the preceding phylum. Here too are placed the
17
258 PHYLUM IX. PTERIDOPHYTA
Marattias (Order Marattiales), large, very leafy ferns
of the tropics, formerly abundant, now nearly extinct,
and with them may be placed the aquatic Quillworts
(Order Isoctales) with slender rush-like leaves. The
latter produce two kinds of spores, viz. microspores
which are small, and megaspores which are much larger.
The plants are thus heterosporous, in contrast with
the preceding which are isosporous. The microspores
produce minute antheridial gametophytes (microgame-
tophytes), and the megaspores, larger archegonial
gametophj'tes (megagametophy tes) .
2. Modern Ferns (Class Leptosporangiatae) develop
their sporangia from superficial cells.
461. These are our common ferns, and this class
includes the greater part of the species now living. In
them the sporangia are usually developed on the lower
surface of the leaves in clusters ('' sori ") of various shapes,
and these may be naked or covered
with an indusium. The mature spor-
angium (spore-case) in most common
ferns has a ring of thicker cells ex-
tending around it. When these be-
come (hy, they contract in such a way
„ ,^, ,, , as to break open the spore-case and
Fig. 13o. — Modern ^ ^
ferns (sporangium and thus sct the sporcs free. Most Modcm
son). 'â–
Ferns are terrestrial, and hence may
be set off as Land Ferns (Order Fili gales), in which
are the less common CHmbing Ferns (Lygodium), Tree
Ferns (FsunWy Cyatheaceae) , Filmy Ferns (Family //?//rteno-
phyllaceae), and Common Ferns (Family Polypodiaceae).
In the last-named family nearly all of the ferns of our
woodlands are found, including such species as the
common Polypody (Polypodiiim vulgare), the Golden
Fern of California {Gymnograrnme triangularis), the
WATER FERNS 259
Maidenhair of the North {Adiantum pedatum), and of
the South {A. capillus-ve?ieris) , the common Brake
{Pteridium aquilinum) the Spleenworts (Asplenium) of
many species, the Shield-ferns (Aspidium), also of many
species, the curious little Walking- fern {Camptosorus
rhizophyllus), the Bladder-fern (Filix fragilis) and the
large Ostrich-fern {Onoclea struthiopteris) .
462. Some of the Modern Ferns have become aquatic
and hence are known as Water Ferns
(Order Marsiliales) in which two kinds of
spores ("heterospores") are produced, mic-
rospores and megaspores, which in time give
rise respectively to antheridial, and arch-
egonial gametophytes. The Marsilias are
rooted plants, with floating, 4-parted leaves,
while the Salvinias are small, floating, nearly rootless
plants, with simple leaves.
Laboratory Studies, (a) Collect several different kinds of
common ferns, including the underground portions as well as
the leaves. Study the vascular bundles, stone tissue, and
fibrous tissue in the underground stem.
(6) Examine the disposition of the small vascular bundles in
the leaves, whether free or reticulated. Peel off a bit of epider-
mis from both surfaces, and study the breathing-pores.
(c) With a low-power study the sori (clusters of spore-cases),
using top light only. The sporangia maj^ be seen and their
attachment made out in this way in those cases where there
is no indusium covering the sorus.
{d) ]\lake a vertical section through a sorus and stud}' care-
fully, looking for the ring of darker cells on the spore cases.
(e) Gametophytes of ferns may often be found in plant-
houses on or in flower-pots near ferns. They may be obtained
also by sowing the fresh spores in flower-pots and keeping them
in a warm damp place (a greenhouse is best). In a month or
two the gametophytes will be full grown. Collect a few of
these of various sizes, carefully wash off the dirt from the under
side, then mount in water, and examine the untlcr surface for
260 PHYLUM IX. PTERIDOPHYTA
antherids and archegoncs. By careful searching j^oung
fernlets may be found still attached to the gametophytes
(prothallia).
(/) If possible secure specimens of Adder-tongue, and com-
pare the structure of the sporangia with the foregoing.
(g) Search the borders of lakes, ponds, and slow streams for
Marsilias. They may probably be found in every part of
the country, although they are rarely collected.
(h) Where possible compare the structure of the sporangia
and sori of Marattias (from greenhouses) with those of common
ferns.
(i) In some places it is possible to secure sporophytes of
Isoetes for a comparative study.
0") Try to secure fresh spores of Isoetes or Marsilia for a
study of heterospores, and of the antheridial, and archegonial
gametophytes.
LITERATURE OF PTERIDOPHYTA
D. H. Campbell, The Structure and Development of Mosses and
Ferns, New York, 1905.
N. L. Britton and Addison Brown, Illustrated Flora of the
Northern States and Canada, Second Edition, New York,
1913.
B. L. Robinson and M. L. Fernald, Graifs New Manual of
Botany, New York, 1908.
J. K. Small, Flora of the Southeastern United States, Second
Edition, New York, 1913.
L. M. Underwood, Ferns and Fern Allies, New York, 1905.
CHAPTER XVI
PHYLUM X. CALAMOPHYTA
THE CALAMITES
463. As far as we know them the Calamites are green
plants in which the marked difference between the small
gametophytes and the large sporophytes seen in the
Ferns is continued, but here the sporophyte stems are
mostly hollow and jointed, and the leaves relatively
small. A great difficulty in studjdng the plants of this
phylum is that although common in the Paleozoic
period, but few (about 24 species) have survived to the
present time, and our knowledge of them is confined to
what w^e have been able to make out from fragmentary
fossils, helped out in some details by a study of the
surviving species.
464. This much, how^ever, has been made out pretty
certainly: Gametophytes small, and short-lived, mostly
monoecious; Sporophytes large, long-lived, with roots,
and elongated, cylindrical, jointed, often hollow stems,
bearing relatively small whorled leaves at the joints;
spores alike (isospores), or of two kinds (heterospores),
borne in cones of sporophylls (i.e. special spore-bearing
leaves).
465. Like the Ferns the Calamites have well-developed
tissues in the sporophyte generation; the vascular
bundles are of a higher type ("collateral"), and are
arranged in a cylinder in the stem. When these bundles
are "open" the stems have the power of increasing in
261
262 PHYLUM X. CALAMOPHYTA
diameter. The epidermis is abundantly supplied with
stomata.
466. The Wedge-leaved Calamites (Class Spheno-
phyllineae) were Paleozoic herbaceous
plants of moderate dimensions, whose sporo-
phyte stems Avere solid, jointed, grooved ex-
ternally, and at the joints bore spreading
whorls of wedge-shaped leaves. Their iso-
spores were borne in terminal cones com-
posed of whorls of 1- or 2-sporangiate spor-
ophylls. Sphenophyllum is the typical genus.
467. In the Horsetails (Class Equisetineae; of the
present, the plant-body of the sporophyte
consists of a hollow, elongated and jointed
herbaceous stem, bearing whorls of narrow,
united leaves, which form close sheaths; the
stem is grooved, and is usually rough and
hard from the large amount of silica depos-
ited in the epidermis.
468. The branches, w^hen present, are in
whorls. Both the main axis and the branches are in
most cases richly supplied with chlorophyll-bearing tis-
sue; but in some of the species the stems which bear
the spores are destitute of chlorophyll. All of the
species have underground stems, which bear roots and
rudimentary sheaths, and which each year send up the
vegetating and spore-bearing stems.
469. The Horsetails are perennial plants. In some
species the underground portions, only, persist, the
aerial stems dying at the end of each year; these are called
the annual-stemmed species. In other species the
aerial stems persist; they are hence known as perennial-
stemmed.
470. The epidermal cells are mostly narrow and
HORSETAILS 263
elongated. The stomata which are present in all the
chlorophyll-bearing parts of the plant, are arranged with
more or less regularity in longitudinal rows; on the stem
they occur in the channels between the numerous ridges.
The vascular bundles of the stem are disposed in a cyl-
inder and run parallel with each other from node to
node, where they join with one another. They contain
tracheary, sieve and fibrous tissues, arranged somewhat
as they are in the bundles of flowering plants.
471. The spores of Horsetails are produced in cones at
the summit of the stems. The cones are composed of
crowded whorls of shield-shaped leaves (sporophylls),
each of which bears upon its under surface five to ten
sporangia. The spores are spherical, and at maturity
the outer wall spUts spirally into four narrow filaments
{elaters) which unroll when dry, and roll up around the
spore again when moistened. Their office seems to be
to aid in setting the spores free from the spore-cases. The
spores germinate soon after falling
upon water or moist earth, enlarg-
ing and successively dividing until
a fiattish irregular gametophj'te
(the prothallium) a few milli-
meters in l)readth is produced. It
bears antherids and archegones ^Jj - JS'-'/S'SyTo,).
resembling those of the ferns upon
its lobes or their edges; in some cases both sexual organs
are on the same gametophyte, while very commonly
they are upon separate gametophytes, although the
spores show no differences. The sperms are spiral and
multiciliated.
472. This class contains but one family (Kquisc-
taceae), including a single genus,' Eciuisetum. and twenty-
four species of herbaceous plants usually a meter or less
264 PHYLUM X. CALAMOPHYTA
in height, but in certain tropical species attaining a
length of 10 meters or more. Among the better known
are the Common Horsetail {Equisetiim arvense), which
sends up short lived, pale or brownish cone-bearing stems
in spring, and profusely branching green stems in sum-
mer {E. telmateia, the Great Horsetail of Europe and our
own Northwestern region, resembles, but is larger than,
the Common Horsetail); the Woodland Horsetail {E.
sijlvaticum), whose green cone-bearing stems branch
profusely after fruiting, and persist all summer; and the
Scouring-rush, called also Dutch Rush {E. hiemale),
with green, branchless stems which produce cones, and
survive the winter. The genus Equisetum originated in
the Paleozoic period, and so is ver}^ old. Some of its
species have become extinct, as is the case with several
related genera.
473. The Old Calamites (Class Calamarineae) were
Paleozoic plants whose sporophytes were
often trees, with hollow, jointed stems,
whose collateral vascular bundles allowed
an increase in diameter by the develop-
ment of a cambial zone. The leaves
were separate, narrow, and whorled at
op^'yte^anifspo^ea the joiuts of the stcm. The heterospores
of Old Caianute. ^^^^^ bome in terminal cones composed
of whorls of sporophylls, each bearing one or more spo-
rangia. Only fragmentary fossils of these plants are
known.
Laboratory Studies, (a) Collect in early spring a number
of cone-bearing stems of the Common Horsetail. Note the
joints (nodes), bearing whorls of united flat leaves, and the
cone, composed of whorls of shield-shaped leaves (sporophylls).
Split the cone and stem and note that the latter is hollow, with
closed nodes.
(6) Carefully dissect put a single sporophyll from the cone,
LABORATORY STUDU-.S 265
and examine it, using a low power. Note the sac-shaped spore
cases upon the under side of the leaf. JMount some of the spores
dry, using no cover-glass, and examine with the 16 mm.
objective. Breathe upon the spores very gently to moisten
them, and notice the coiling of the elatcrs; observe the quick
uncoiling which takes place upon the evaporation of the
moisture.
(c) Sow a quantity of the fresh spores upon moist earth or
porous pottery, covering with a bell-jar and taking every pre-
caution to secure constant moisture. The spores will begin to
germinate in a few days, when studies of successive stages of
growth may be taken up. By care the mature gametophytes
(prothallia) may be grown, and the antherids and archegones
studied.
{d) ]\Iake ver}^ thin cross-sections of the stem of the Common
Horsetail. Note the position of the vascular bundles. Now
make a vertical section of the bundles and study the tissues,
using high powers.
(e) Study the breathing-pores on the green stems of the Com-
mon Horsetail. Compare these with those of the Scouring
Rush. Study also the disposition of the chlorophyll-bearing
tissue in cross-sections of both stems.
(/) Examine underground stems of Horsetails, and compare
the structure with that of the aerial stems. Make cross-sec-
tions of the roots which are attached to these underground
stems.
LITERATURE OF C.ALAMOPHYTA
The same as for the preceding jihylum, and
M. C. Stopes, Ancient Plants, London, 1910.
CHAPTER XVII
PHYLUM XL LEPIDOPHYTA
THE LYCOPODS
474. Here as in the Calamites we are dealing with a
phylum from which many of the forms have disappeared
through extinction, leaving only their fragmentary
fossils. Yet here again by a study of the plants that
have survived, and a comparison of their structure
with such fossil remains as have been found, we may make
out pretty clearly the nature of the plants that constitute
this phylum.
475. Accordingly the Lycopods may be characterized
as chlorophyll-green, terrestrial plants, exhibiting two
generations in each hfe-cycle, viz. : (1) thegametophyte,
which is small, short-lived, and typically tuberous or
globose, with few rhizoids or none, and often dioecious;
the sexual organs are deeply sunken, and the sperms
are biciliated; (2) the sporophyte, which is large and
long-lived, with roots, a solid, continuous (not jointed)
stem, and many small spirally arranged or opposite
leaves, some of which, the sporophylls, with sporangia
in their axils, are in terminal cones. The spores are
mostly heterosporous. The tissues of Lycopods re-
semble those of Ferns and Calamites in both number
and kind. Their vascular bundles are essentially Uke
those of the Ferns (concentric), and in some cases are
separate, while in others they are consolidated into a
central compound bundle, surrounded by a mass of thick-
266
GROUND PINES
267
walled fibrous tissue. The epidermis is abundantly
supplied with stomata.
476. The phylum contains about 700 living species,
and consists of two quite distinct classes, viz.: The
Lower Lycopods (Class Lycopodineae) mainly dis-
tinguished by being isosporous, and the Higher Lycopods
(Class Lepidodendrineae) which are heterosporous.
477. In the first we find the Ground Pines (Family
Lycopodiaccae), otherwise known as Club-mosses, which
are terrestrial, perennial, evergreen plants with many
small, generally moss-like leaves cover-
ing the stems. The sporophylls are
often crowded toward the summits of
certain branches, in some cases form-
ing well-marked cones (strobili). The
spores are all of one kind, and are
borne in roundish sporangia of which
there is one on the upper surface of sperms, archegon
each leaf near the base.
The Ground Pines are common in the Appa-
lachian region, Canada, and northwestward, and all
belong to the genus Lycopodium, including L. clavatum,
L. complanatum and L. dendroideimi, all ex-
tensively used in Christmas decorations. Fos-
sil specimens of Ground Pines from the Paleo-
zoic period have been recorded.
478. In the second class are the Club-mosses
(Family Sclaginellaceae) which resemble the
Ground Pines, but in our common species are
generally smaller and more moss-like, and
have (with few exceptions) four-ranked leaves.
Their sporangia occur singly on the sporophylls
which are clustered into terminal spikes (cones). The
spores arc of two kinds: the small ones (microspores)
Fig. 141. — Lycopodium
(gainetophyte, antherid.s,
ea and
©qo
Fig. 142.—
Lycopodium
(sporophyte,
sp o r a n gia,
Bpores).
268 PHYLU:\I XI. LEPIDOPHYTA
which are very numerous in their sporangia, and the
hu'gcr ones (megaspores) which are mostly four in each
sporangium. These microsporangia and megasporangia
are intermingled in the cones. When mature the
microspores fall out and are blown awa}^, but it often
happens that the megaspores remain in the old wall of
the megasporangium.
479. The gametophytes of the Club-mosses have almost
disappeared. When a microspore germi-
nates, it becomes divided into a consider-
able number of cells, one of which is the
remnant of the gametophyte (prothallium),
while the other cells form one large an-
lagineiia (game- thcrid, each iuncr cell of which produces
tophytes, anthe- , . .,• , i
rid, sperms, ar- blClliated SpCrmS.
c egones, egg . ^g^^ ^^^^ mcgaspore likewise produces a
very small but many-celled gametophyte, which pro-
trudes but little from the ruptured spore-wall. Upon
this several archegones develop. This development
may take place while the megaspore is still enclosed
in the wall of its sporangium. After fertilization the
egg gives rise directly to a leafy
plant, which emerges from the spore-
wall in a way to remind one very
forcibly of the growth of a plantlet
from a seed. This resemblance is
made greater by the hkeness of the ^^^ i 4 4._seiagineUa
first leaves to cotyledons. spo^esf ^^^^' ^ ^ ° ^ ^ " ^ '*•
481. But one genus, Selaginella,
is known in this family. It contains many species,
most of which are tropical. Several species are com-
mon throughout the United States, and several exotic
species are frequently cultivated in plant-houses.
LEPIDODEXDRIDS 209
482. Allied to the Club-mosses are the arborescent
Lepidodendrids (Order Lepidodendrales) which were
abundant in the Paleozoic period, and which disappeared
in the Mesozoic. We have fragmentary fossils of the
sporophytes, which were large dichotomously branched
trees, sometimes 30 meters high and a
meter in diameter. There was a large ^^&^^
central vascular bundle, which how- V^ >t 1^
ever formed a peripheral cambium
so that the stems increased their di-
ameter much as in the case of higher
plants. The stems and branches
were thickly clothed with pointed tZ^TolX'''"' '''''"
leaves a decimeter or more in length,
and when these fell off they left large scars of charac-
teristic shape and arrangement.
483. The fossil remains of the spore-bearing cones, of
which many specimens have been found, indicate that
they contained two kinds of spores. Hence it is certain
that the Lepidodendrids were allied to the Club-mosses.
The more common genera are Lepidodendron, and
Sigillaria.
Laboratory Studies, (a) Secure a few fresh or alcoholic
specimens of various kinds of Lycopods in fruit. Ground
Pines may be collected in many places in the eastern United
States. The Club-mosses may be obtained in plant-houses.
(6) IVIake cross-sections of the stems, and study the vascular
bundles in Lycopodium where they are imbedded in a thick
mass of fibrous tissue. Examine the leaves, noting the small
vascular bundle in the midrib. Stud}' the epidermis, which
contains numerous breathing-pores.
(c) In like manner study Selaginella.
(d) Carefully remove a sporophyll from a cone of Lycopo-
dium, and study the sporangium and spores. Further exami-
nation will show that the spores are of one kind only.
270 PHYLUM XI. LEPIDOPHYTA
(e) Carefully dissect out from the fruiting cone of Selaginella
several sporangia, some with four large spores, and others with
many small spores.
LITERATURE OF LEPIDOPHYTA
The same as for the Ferns and Calamites.
CHAPTER XVIII
PHYLUM XII. CYCADOPHYTA
THE CYCADS
484. Like the two preceding phyla this one is a mere
remnant of a much larger group. All told there are only
about 140 living species belonging to six families, while
we know of as many more families whose species have
become extinct. Enough has been made out as to the
structure of living and extinct forms to enable us to
define the Cycad phylum as follows:
485. Their archegonial gametophytes are so dependent
that they are enclosed in the megaspore, which is itself
retained in the sporangium; the antheridial gametophyte
is minute and free, and its tubular antherid typically
develops two or more multiciliated sperms; after fer-
tilization of the egg the megasporangium becomes a
''seed." The sporophyte is first enclosed in the seed,
where it is nourished by the gametophyte, and later it
escapes by developing roots below, and expanding its
leaves above; eventually some leaves become sporophylls
and develop microspores and megaspores.
486. It is instructive here to compare the higher
Lycopods with the Cycads. In both there are micro-
spores and megaspores, and in both the microspores
always are set free from the sporangium. In both again
the microspore produces a very small (one- to few-celled)
gametophyte. However, the antherid of the higher
Lycopods is a few-celled structure, with many minute,
biciliated sperms, while in the Cycads the antherid is
271
272 PHYLUM XII. CYCADOPHYTA
reduced to a simple tube, which contains usually two
large, multiciliated sperms (suggesting a correlation
between size and the number of sperms). In both
phyla, again, the megaspores develop from a spore
mother-cell (archespore) as tetrads, but while in the
Lycopods all four may become mature,
in the Cycads only one matures. In Ly-
copods the megaspores separate from the
sporangial tissue as they develop, and
normally are set free, while in Cycads
Yia. r46.— Cyoad ^^® smglc mcgasporc remains perma-
fnd sSms!^^' ^^^^ nently connected with and surrounded
by the sporangial tissue. So the embryo
sporophyte of the former normally develops outside of
the megasporangium^ while in the latter it does so in-
side of the megasporangium, and thus forms the seed.
487. The lowest Cycads, the so-called **Seed-ferns"
(Class Pteridospermeae) , were abundant in the Paleo-
zoic period and are now known only from their fossil frag-
ments. They were long thought to be
ferns of an ancient type, but are now
known to have been seed-bearing plants.
Apparently they were derived from the
Marattias among the Old Ferns. Their
leaves were fern-like in shape and struc- fig. 147.— Pterido-
ture. Their stems were capable of in- and seTd. '''°'°''^'^''
creasing in diameter. It is now thought
that the Seed-ferns constituted a group of vast extent in
Paleozoic times.
488. In the Common Cycads of the present (Class
Cycadineae) the sporophytcs are usually erect, woody,
little-branched trees, rooted below, and bearing terminal
crowns of evergreen, pinnate leaves. The collateral
vascular bundles are arranged cylindrically in the stem,
COMMON CYCADS 273
and increase its thickness by the development of their