HOW FERNS GROW

MARGINAL SHIELD FERN. — Frontispiece

HOW FERNS GROW

MARGARET SLOSSON

WITH FORTY-SIX PLATES BY THE AUTHOR

NEW YORK
HENRY HOLT AND COMPANY

1906

Copyright, 1906

By
HENRY HOLT & COMPANY

PREFACE

INNUMERABLE books have been written about ferns in their
mature stages of development, and many accounts exist of their
earliest stages, which end with the formation of the young fern-
plant, but very little respecting the intervening stages seems to
have been recorded. Although in these stages the fern-plant's
development takes place, including the leaf -development, the
literature of the subject consists of a few scattered papers only.
These papers, moreover, deal mostly with individual species, and
chiefly with the subject of cell-growth and kindred phenomena.
They scarcely touch upon the development of the form and ve-
nation of the leaf in each species, and in its individual aspect
only, without reference to its relation to such development in
other fern species.

For these reasons, and in view of the important part that the
form and venation of the species' leaf play nowadays in the
classification of fern species, and of the fact that both often differ
widely in the early stages of the leaf from their characters in the
later, it is thought that to point out in this book the principal
features of the development of form and venation in fern leaves,
as seen in the species of the northeastern United States, will be
useful, and may serve to throw light upon such development in
fern species in general.

In order to give a clearer understanding of the leaf-develop-
ment, in each chapter containing an account of this development

iv Preface

in a single species, the account is preceded by a synoptical descrip-
tion of the fern-plant in its mature stages.

The distribution of the species is mostly quoted from Mr.
William R. Maxon's "List of the Ferns and Fern Allies of North
America, North of Mexico, with Principal Synonomy and Dis-
tribution."* Most of the spore characters cited are quoted from
Prof. D. C. Eaton's "Ferns of North America." With these
exceptions, and a few others noted as they occur, all descriptions
have been drawn from or verified by specimens examined by
myself. I have personally collected in the field or raised from
spores nearly all the young leaves figured and described.

The illustrations of leaves, throughout the book, excepting
where otherwise stated, are life size.

The nomenclature is in accordance with the American code.
Sufficient synonomy is cited to include the more important
synonyms.

I wish to render acknowledgments to all who by their cour-
tesy have aided in any way the preparation of this book. To
Dr. Lucien M. Underwood I am under obligations for kindly
examining the synoptical descriptions of the species, for valuable
suggestions, and for very many kindnesses and courtesies, includ-
ing the privilege of access to important books and specimens.
I wish to express likewise my indebtedness to Mr. George E.
Davenport, for kindness in connection with numerous speci-
mens. To Dr. Henry F. Walker I am indebted in many ways,
which it gives me much pleasure to acknowledge. Miss Kath-
erine Foot also should be especially mentioned. Mrs. N. L.
Britton and members of the American Fern Society have kindly
furnished me with certain notes and specimens.

*Proc. U. S. Nat. Mus. 23: 619-651. 1901.

CONTENTS

CHAPTER PAGE

PREFACE iii

I. DEVELOPMENT OF THE FERN LEAF i

II. WALL-RUE 27

III. MAIDENHAIR 33

IV. HART'S-TONGUE 43

V. POLYPODY 49

VI. PURPLE CLIFF-BRAKE 57

VII. NARROW-LEAVED SPLEENWORT 63

VIII. MAIDENHAIR SPLEENWORT 71

IX. EBONY SPLEENWORT 77

X. CHRISTMAS FERN 85

XL SLENDER CLIFF-BRAKE 93

XII. SILVERY SPLEENWORT 99

XIII. NEW YORK FERN 109

XIV. MASSACHUSETTS FERN . . . . ; 113

XV. MARGINAL SHIELD FERN 119

XVI. SPINULOSE FERN 125

XVII. WALKING LEAF 131

XVIII. NARROW-LEAVED CHAIN FERN 137

XIX. SENSITIVE FERN 145

ILLUSTRATIONS

PLATE PAGE

MARGINAL SHIELD FERN Frontispiece

WALL-RUE I 31

MAIDENHAIR .... II, III 41

HART'S-TONGUE ... IV 47

POLYPODY V, VI, VII 55

PURPLE CLIFF-BRAKE . VIII, IX, X, XI 61

NARROW-LEAVED SPLEEN-
WORT XII, XIII, XIV 69

MAIDENHAIR SPLEENWORT XV 75

EBONY SPLEENWORT . XVI, XVII 83

CHRISTMAS FERN . . XVIII, XIX, XX 91

SLENDER CLIFF -BRAKE XXI, XXII 97

SILVERY SPLEENWORT . XXIII, XXIV, XXV 107

NEW YORK FERN . . . XXVI, XXVII in

MASSACHUSETTS FERN . XXVIII, XXIX, XXX 117

MARGINAL SHIELD FERN XXXI, XXXII 123

SPINULOSE FERN . . ... XXXIII, XXXIV, XXXV .... 129

WALKING LEAF . . . XXXVI 135

NARROW-LEAVED CHAIN

FERN ...... XXXVII, XXXVIII, XXIX, XL, XLI 143

SENSITIVE FERN . XLII, XLIII, XLIV, XLV .... 153

CHAPTER I

DEVELOPMENT OF THE FERN LEAF

AMONG the reasons for which study of the development of
form and venation in fern leaves appears desirable, the following
are conspicuous.

In many cases, leaf characters supposedly specific are features
of only comparatively late stages of development of the species'
leaf. As might be expected from that fact, this development
sometimes, by exceeding its usual limits, partly or wholly ob-
literates such characters. In any delimitation of fern species, it
is thus necessary to take into consideration the leaf-development
of each species. In order to do this, and sometimes .also in order
to distinguish between what is due to this development and what
is due to subspecific or other variation, it is necessary to know
something of the modes of development of the form and venation
of the leaf of each species in question. Instances are not wanting
in which failure to understand the phenomena of such develop-
ment has misled fern students into interpreting different stages
of one species' leaf as leaves of different species or of different
varieties of the same species.

It is evident that in many cases a clearer conception of the
genetic affinities of fern species can be formed with knowledge of

2 Development of the Fern Leaf

the sum of the stages of development of the form and venation of
the leaf in each species, than with knowledge of isolated stages,
however advanced, alone. This is especially true if, as there
seems reason to believe,* traces of each of these plants' descent
are to be seen in phases of the plant's leaf during its develop-
ment.

Most fern students, however, cannot easily obtain more than
isolated and, usually, mature stages. It seems, then, worth while
to ascertain, if possible, both the various modes of development
of form and venation in fern leaves, and the various effects pro-
duced by these in the leaves, in order that the modes of this
development in any species' leaf may be recognized from isolated
stages of the leaf, and a working knowledge of the missing stages
thus gained.

It is proposed to outline in this chapter the different modes of
this development, as shown in the fern species of the northeastern
United States, and to point out in succeeding chapters various
effects produced by these in the leaves of certain of the species.
Such species have been included as serve to represent a wide
diversity of effects. While the account contained in this chapter
is based principally on specimens of the species of the northeastern
States, it has been confirmed on examination of very many speci-
mens of other species.

The development of the fern species' leaf from the first to
the adult stage is exemplified, as fern students know, not in a
single leaf, but in a series of leaves. This series is borne by the
fern-plant, which is technically known as the sporophyte. The
leaves of the series, which begins with the first leaf produced by

* See p. 8.

Development of the Fern Leaf 3

the young plant as it arises from the prothallus, portray succes-
sively the successive changes that the species' leaf undergoes in
its development. After the mature stages of leaf-development
are reached, leaves continue to form on the plant, but, at least as
a rule, portray only the mature phases of the species' leaf.

The degrees of development shown by the individual leaves
of the series illustrative of leaf-development vary in different
plants of the same species. The degree shown by any one leaf
of the series borne by any one plant is commonly more or less
greater than that shown by any one of the leaves preceding this
leaf in the series, and more or less smaller than that shown by
any one of those following, but bears no other relation to the de-
gree shown by any leaf of the series. The discrepancy between
the degrees shown by any two consecutive leaves of any series
may be minute or larger or even great. The number of leaves
composing the series of any one plant of a species is thus not
necessarily the same as the number composing the series borne
by any other plant of that species.

The development of the species' leaf as a whole commonly
advances steadily, but the development of its parts often fluctu-
ates. For example, given two consecutive leaves of the series of
leaves illustrative of leaf -development, the degree of development
of the second leaf as a whole is commonly greater than that of
the first, but the degree of development of one of its parts is often
less than that of the corresponding part of the first, while the de-
gree of development of the corresponding part in the leaf next
succeeding these two leaves in the series may or may not be
greater than that of the corresponding part in either of the two.
Even after the mature stages of leaf-development have been

4 Development of the Fern Leaf

reached, while two leaves of the same plant may as wholes agree
approximately in point of development, the degrees of develop-
ment of similar parts in these leaves may or may not be uniform :
but this is almost equivalent to saying merely that no two leaves
are likely to be exactly alike.

It is evident that under the above conditions, if we want a
complete series of leaves illustrative of the gradations of change
that a species' leaf undergoes hi its development, we shall proba-
bly not be able to find it in the series of leaves borne by any one
plant, but we may be able to select the leaves necessary to form
it from the series borne by different plants of the species.

It is also evident that, while there is apparently no certainty
that any one of the leaves of the series borne by any one plant
shall match in points of development any leaf of the series borne
by any other plant, instances may occur in which one does. It will
also be seen that instances may occur in which leaves portraying
certain stages of development usually or always appear, under
normal conditions, in the series borne by each plant of a species,
however the leaves preceding or following them may vary in
degree of development in the cases of the different plants. I
have found, on examining a large number of young plants of
each of certain species, taken from different localities, that nearly
all the first leaves produced by the plants of each of these species
portrayed the same stage of development.

It is often difficult to say at what stage of development the
species' leaf becomes mature. We can scarcely say at the stage
when it first bears sori, for in some species this stage appears to
be different with different plants, and in some the leaf bears sori
at an extremely early stage. Nor can we say at the ultimate

Development of the Fern Leaf 5

stage only of normal development, for this stage, as will be seen
farther on, is apparently attained, in the cases of at least some
species, under particularly favorable conditions only, so that the
leaves of many plants of a species may never portray it, that
nevertheless reach a fair size, compared with the more highly
developed leaves, and bear sori freely. For practical purposes
we may, however, regard as mature both those leaves that have
attained the latter state of development and those more highly
developed.

The species' leaf on becoming fertile often becomes modified
in character. The change is sometimes very great, as in Onoclea
sensibilis. It is often slight. When it occurs, often only those
leaves that portray the two extremes of the transition are to be
seen on some plants, or on those plants at certain times, but in
such cases it sometimes, if not always, happens that leaves portray-
ing the intermediate stages are to be seen either on the same
plants at other times, or on other plants. A series of leaves illus-
trative of the transition can thus be collected in the same manner
that a series of leaves illustrative of the leaf's development can be
collected.

The degree of development and the size of each successive
leaf of the series illustrative of leaf-development borne by the
individual plant seem to be governed to some extent by the
plant's degree of vigor. The leaves of the vigorous plant are apt
to be considerably larger than the leaves of the weaker, even
than such as happen to portray the same stages of development.
In addition, if the plant is vigorous, the discrepancy between the
degrees of development shown by any two consecutive leaves of
the series is apt to be greater, so that the series consists of fewer

6 Development of the Fern Leaf

leaves and the mature leaves in consequence appear sooner than
if the plant is weak: the first leaf, also, produced by the plant
often portrays a more advanced stage of development and the
height of leaf-development attained is sometimes greater. The
leaves of a sickly plant often portray minute gradations of change.

There is evidence which tends to show that if a plant's vitality
be suddenly lowered, as, for example, by an injury, the first leaf
the plant produces afterward may portray a lower stage of de-
velopment than the last leaf it produced before, and it may or
may not produce additional leaves before the height of leaf-
development previously attained in its series of leaves is again at-
tained. But more evidence is needed on this point. The most
striking apparent case of the kind that I have seen is the follow-
ing:

The series of leaves produced by a young plant of Asplenium
ebenoides had passed the stage of leaf -development at which, in
this species, the leaf is simple, and had reached the stage at which
the leaf is deeply pinnatifid, when the flower-pot containing the
plant was broken and only a little earth left on the roots. The
plant was allowed to remain in this condition for some days
before it was re-potted, and some of its leaves were cut off. It
then produced simple leaves again, and then a series of leaves
leading again to the pinnatifid stage. But as A. ebenoides is a
hybrid, and as one of the parent species has simple leaves, the
case can be called merely one of temporary partial reversion to
a parent type.

It is evident that conditions of environment can lessen or
increase a plant's vigor, and so indirectly lessen or increase the
degrees of development shown by its leaves individually. Little

Development of the Fern Leaf 7

is known of the various other ways in which it may be possible
for conditions of environment to affect these leaves.

In the cases of some species the extreme height of leaf-
development seems to be attained under certain conditions only.
These conditions, whether of environment or not, apparently are
often such as tend to produce extreme luxuriance and fertility in
the plant. It will readily be seen that this is not remarkable;
that if a species' leaf has a tendency to develop along certain
lines, under conditions particularly favorable to the plant's
growth, development of the leaf might easily be carried along
those lines farther than usual, or sometimes farther than ever
before. Among our northeastern ferns we have apparently, in
Polystichum acrostichoides, at least one authentic case of a species
in which the plants, under certain conditions of environment,
produce leaves portraying a height of leaf-development far be-
yond the usual one, and lapse to their usual state when the con-
ditions are altered in certain respects, producing then the usual
mature leaves only.

It is a well-known fact that conditions of environment some-
times apparently induce changes in a species' leaf. Conditions
of environment acting upon the plant, during the period of the
leaf-development, or even upon the individual leaves of its se-
ries illustrative of this development, during their formation, can-
not, however, be said to account, at least in the cases of certain
species, for some of the changes that the species' leaf undergoes
in its development; for these changes are seen to be the same
under conditions of environment obviously widely different. For
instance, I have seen the leaf of Asplenium platyneuron undergo
the same changes in the series of leaves borne by plants growing

8 Development of the Fern Leaf

in sand mixed with leaf -mold, on a bank near the sea, on Shelter
Island, New York; in the series borne by plants growing on
rocks, on an exposed hillside, in central Vermont; and in the
series borne by plants raised in mixed soil in flower-pots kept
under glass in a greenhouse.

There is, however, one hypothesis which offers a rational
explanation of such changes; namely, that in the species' leaf
during its development are indicated characters that the leaves
of the plant's ancestry possessed. That is what we should expect
to be true if we accept as true the alleged fact that in other living
things traces of the individual's ancestry are to be seen in
changes which take place in the individual during its develop-
ment from the first to the adult stage.

The fact that, in the case of ferns, the changes in the leaf,
which is a part of the fern individual, are exemplified in a series
of successive ephemeral leaves rather than in one persistent leaf,
need not militate against this hypothesis; which finds support in
such facts as the following, difficult to account for on any
other.

(i) In some species peculiarities are present in the early
stages of the leaf which disappear in the later stages: in some
peculiarities are absent in the first stages which appear and are
gradually intensified in the later. For example, in the early
stages of the leaf of Nephrokpis exaltata, according to Mr. A. A.
Eaton,* the leaf's pinnae are crisped and bristly at margin with
excurrent nerves, but lose these characters as the leaf becomes
mature. In the first stages of the leaf of Polystichum acrostichoides
spinulose points on the leaf's margin are absent, but in later

* See Fern Bull, n: 47, 1903.

Development of the Fern Leaf 9

stages they appear, first as one or two here and there, then grad-
ually increase in number, and finally become extremely numerous.

(2) In the mature stages of the leaf of at least one species,
appendages to the leaf are present which seem to be both out of
place and a bar to the symmetry of the leaf, but which retain
their positions in the preceding stages until an early stage is
reached in which the leaf is so altered in form that they consti-
tute an integral part of it. For example, in the mature stages of
the leaf of Adiantum pedatum a single leaflet is present below the
basal pinnae on one half of the dichotomous rachis. There
appears to be nothing about the leaf at this stage of development
to account for its presence, and no corresponding leaflet on the
other half of the dichotomous rachis; but this leaflet retains its
position in preceding stages until a stage is reached in which
the section of stalk that later forms the section of dichotomous
rachis bearing the leaflet constitutes the base of the rachis of a
pinnate branch, and the leaflet constitutes one of the basal
leaflets of that branch.

Owing to lack of space, additional evidence tending to confirm
the truth of the above hypothesis cannot be cited here, but it is
believed that the reader will continually find such evidence, both
in facts cited elsewhere in this book and in those that come
under his own observation.

The development of the fern leaf, while characterized by other
particulars as well in individual cases, may be said to be char-
acterized in general by change in the leaf's form and by increase
in the leaf's size and in the complexity of the leaf's venation.
This is true whether the leaf is simple at first and remains simple
throughout its development, whether it is simple at first and

io Development of the Fern Leaf

becomes compound later, or whether it is compound from the
first.

The development of the form of the leaf that is simple at
first and remains simple, while obviously differing in different
species according to the phases through which the leaf passes
and the ultimate form to be produced, need not be described
here.

The development of the form of the leaf that is simple at first
and becomes compound later, and of the form of the leaf that is
compound from the first, can be best understood by ascertaining
the various ways in which simple leaves become compound and
compound leaves more so. In the following description of the
ways in which this occurs in our northeastern ferns, for the sake
of brevity, each of the various processes will be described as if
continuous and taking place in a single leaf, but the reader will
bear in mind that in reality each is exemplified in a series of
leaves.

The student of actual specimens illustrating these processes
will find it necessary to bear in mind also that, (i) as the com-
plete series of leaves is not likely to be borne by any one plant,
and (2) as it could scarcely be considered remarkable if
some steps in any one of the processes, although portrayed at
first, should in the course of time come to be partly or wholly
obliterated, as a rule, in the series borne by the plants of a species,
hence, (3) that failure to find some steps portrayed in the series
borne by one plant, or even in the series borne by many plants
of a species, which often occurs, does not necessarily mean that
these steps are not portrayed at the time or have not been por-
trayed at some former time in the series borne by any plant of

Development of the Fern Leaf 1 1

the species in question. The remarkable part of it is, not that we
should find, as we do, some steps missing in the case of some
species, but that we should find, as we do, so few steps missing
in the case of many species. Often the gradations of change
from a simple leaf or leaflet to a compound one are so minutely
portrayed that the series can be likened to a series of photo-
graphs, taken by a kinetograph, of a single leaf undergoing
actual enlargement and subdivision.

For a simple leaf or leaflet to become compound, and for a
compound leaf or leaflet to become more compound, one or
more incisions, according to the number of segments* to be
formed, must occur in the leaf or leaflet. Often the appearance
of such an incision is first indicated by a shallow sinus or small
notch in the leaf's margin. This sinus or notch then deepens
and so forms the incision.

If enlargement of the segments takes place (and it usually
does), it may take place during, before, or after formation of the
incision or incisions by means of which the segments are formed.
Sometimes the portion of leaf that is to become a segment
elongates in the direction its apex is to take before any incision
that is to separate it from the remainder of the leaf is even indi-
cated. In such a case, a more or less extended lobe is formed.
We have examples of such lobes in some of those often seen
at the bases of the divisions of the leaf-blade in Pellaa atropur-
purea. In the latter plant the incisions setting free the lobes

* The term "segment" is used here and generally throughout this book, not in its
restricted sense, in which it means "one of the lobes of a pinnatifid leaf or leaflet," but
interchangeably with the term "leaflet," as meaning "one of the subdivisions into which
a leaf or leaflet naturally divides." For example, the pinna of a pinnate leaf is a "seg-
ment" or "leaflet" of this leaf.

12 Development of the Fern Leaf

mostly appear, but in some plants development of the segments
is arrested before incisions appear. A case in point is afforded
by Camptosorus rhizophyllus. Lateral prolongations are some-
times seen at the base of the leaf-blade of this plant. These
have never, so far as I know, been found separated from the
main part of the leaf by incisions, yet their position and
character show that they are to be regarded as partly formed
segments.

The position of each incision that divides each leaf or seg-
ment of a leaf into segments depends largely upon the character
of the leaf's venation ; in what way will be seen from the follow-
ing description of the different kinds of venation and their modes
of development as seen in the leaves of the species of the north-
eastern United States.

These kinds of venation are:

( i. Pinnate. f

FreeK 3. Flabellate. Anastomosed 2. Pinnate.
( 4. Unilateral. (

In the leaf with free pinnate venation the leaf -blade, and
each of the leaf's segments, if there are any, are entered at base by
a vein that extends longitudinally through it in the form of a mid-
vein which bears branches on both sides. These branches, each
of which has its base attached to the midvein, are the midvein's
"primary branches." They are usually either alternate or oppo-
site, and are either simple or bear branches.

When the leaf or segment subdivides into segments, the
incisions, by means of which the segments are formed, occur be-
tween the primary branches of its midvein. In our north-
eastern species the first incision between these branches that oc-
curs on either side of the midvein usually occurs between the two

Development of the Fern Leaf 1 3

lowest primary branches on that side, and each successive inci-
sion, except the first, occurring on either side, normally occurs
between the two primary branches next above the last incision
previously formed on that side.* Each new segment thus con-

b
FIG. i.

FIG. 2.

tains one of the mid vein's primary branches, including its ram-
ifications, if any, and this branch, unless its development be
arrested first, develops into the segment's midvein, bearing
branches on both sides. This will be readily understood from
figures 1-4.

In figures 1-3 the partial subdivision of a primary segment,

FIG. 3.

of a leaf with free pinnate venation, into secondary segments of
the leaf, is shown. In Fig. 4, which represents a section of this
primary segment, the ending of this subdivision and the begin-

* In some foreign species the incisions, while occurring between the primary branches
of the midveins in such a way that each segment formed by them contains one of these
primary branches, occur at wider intervals than as above described, some primary branches
without incisions between them intervening between the new segments.

14 Development of the Fern Leaf

ning of subdivision of the secondary segments into tertiary
segments is shown. In Fig. i, the beginning of the incisions
between the primary branches of the segment's midvein, by means
of which the secondary segments are to be formed, is in some
places not evident, and in others indicated by barely perceptible
indentations of the leaf's margin. In Fig. 2 it is marked, and
in Fig. 3 these incisions are pronounced.

In Fig. 4 some of these incisions have almost, and others
quite, reached the midvein, so that the secondary segments are

FIG. 4.

practically distinct, and the incisions, by means of which the
secondary segments are to be divided into tertiary segments,
have begun to form between the primary branches of the second-
ary segments' midveins.

In Fig. i the primary branches of the segment's midvein
vary in degree of complexity. Those close to the apex of the

'5

segment are simple ; those below, by lengthening and sending
out branches, have begun to develop into the midveins that
they finally become in the secondary segments, although these
segments are not as yet formed. In Fig. i a this development
of a primary branch into a midvein has but just begun: the
primary branch may be described either as once forked or as an
incipient midvein not developed beyond its two first (basal)
primary branches, which are simple. In Fig. i b this develop-
ment has been carried a step farther, in Fig. 2 c another step, and
in other segments of Fig. 2, in some of Fig. 3, and in the second-
ary segments of Fig. 4, successively still farther. In Figs, i
to 3 may be seen the early stages of the similar development of
the primary branches of the newly-formed midveins into the
midveins they are to become in the tertiary segments.

The development of the primary branch of one midvein
into another midvein with primary branches is brought about,
as may be seen from the above examples, by the primary branch
repeatedly lengthening and sending out successive primary
branches of its own on both sides. This development may
begin before, during, or after the formation of the incision or
incisions by means of which the segment that is to contain the
new midvein is formed. At the same time the branches pro-
duced by the latter midvein may or may not begin to develop like-
wise. Within reasonable limits, there are apparently no bounds
to the degree of complexity the primary branches of a midvein
may attain before or during the formation of the incisions that
set them apart to constitute midveins. On the other hand, the
branches produced by a mid vein's primary branch during its
development into a midvein may, if appearing before the seg-

1 6 Development of the Fern Leaf

ment that is to contain the latter midvein is fully formed, i.e.,
distinct, remain simple until this segment becomes distinct.
There are also cases in which all the primary branches of each
midvein and incipient midvein of a leaf are simple when first
produced, and incisions, forming distinct segments, occur between
them coincidently with their production: in these cases the seg-
ments appear to be made up of lobes containing each a simple
vein. It is a question, however, if in the latter cases the vena-
tion can be called pinnate. It approaches closely the free fla-
bellate type.

The depth to which the incisions between the primary branches
of the midvein or midveins are carried in any part of a leaf
determines whether the segments formed by them shall be partly
formed or distinct, and if distinct whether adnate or not adnate
to the rachis. For example, in Fig. 4 the incisions between the
secondary segments are carried only far enough to render these
segments practically distinct and adnate to the primary seg-
ment's midvein, which now constitutes a rachis. If these in-
cisions had been extended, at the points where they cease in
Fig. 4, along the edges of the rachis as far as the midveins of
the secondary segments, these segments would have been sessile
instead of adnate to the rachis. If the latter midveins had been
lengthened at base, or the incisions had extended a short way up-
ward beside them, these sessile segments would have been ren-
dered stalked.

I have found that neither the primary branches of the mid-
veins of a species' leaf nor the segments formed by incisions be-
tween these branches appear uniformly either opposite or alternate
in all the leaves of any species with pinnate free venation that I

Development of the Fern Leaf 17

have examined, although in some species they have appeared
much more nearly so than in others. Occasionally two on one
side of the midvein intervene between two on the other, but for
the most part they appear to vary from opposite to alternate.
The apparent positions, on the mid veins, of the primary branches
between which the incisions occur have been taken as criteria
in determining the positions of the segments formed by these
incisions, instead of the positions of the ends of the incisions,
since the latter vary according to the degree of development of
the segments. But the exact positions of these branches on the
midveins can only be determined by examination of cells of the
leaf, which I have not attempted.

It will be noted that in Figs, i to 4 the successive segments,
whether partly formed or distinct, whether entire, cleft, or divided,
continually elongate at apex, their midveins also lengthening and
sending out new primary branches in succession above those pre-
viously formed. This and a similar lengthening of the leaf -blade
at apex are common occurrences in the development of fern
leaves. To one or both the long tapering tips of some compound
leaves are due in many cases.

It will also be noted that the forms of the segment belonging
to the primary series of segments of the leaf, shown in Figs, i
to 3, are essentially duplicated by the forms of the segments be-
longing to the secondary series, shown in Fig. 4. Duplication of
the forms of the segments of one series by those of succeeding
series is often seen when, as in the section of leaf here figured,
formation of the segments of one series upon those of another is
not particularly evident until the latter segments have become
fairly large, comparatively speaking. It is also often seen when

1 8 Development of the Fern Leaf

formation of each successive segment of each series is not begun
until the segment preceding it on the same side of the midvein
has become distinct. It is often absent when formation of the
segments of one or more succeeding series is begun upon segments
of one series while the latter segments are still in an incipient
state. Instances of the latter kind are often seen in very young
leaves: in such cases the effect of clusters of lobes is often pro-
duced. An analogous and particularly common case is the begin-
ning of the formation of segments on a leaf -blade when the forma-
tion of the leaf-blade itself has barely begun.

From the above account some idea can be formed of the
diversified results that may be produced in a leaf with pinnate
free venation, by the simple occurrence of incisions between the
primary branches of the leaf's midveins, with or without enlarge-
ment of the segments so formed and with or without development
of a midvein from the primary branch, as a base, contained
within each segment.

Anastomose pinnate venation differs from free pinnate vena-
tion in that the midveins bear, instead of free branches, branches
that unite with one another, usually by means of their veinlets.
Between the two kinds of venation all gradations exist, as the
result of some veins uniting and others of the same leaf remain-
ing free. The occurrence of an occasional areole in a leaf whose
venation, as a rule, is wholly free is common

It is a curious fact that in all four of our northeastern species*
whose leaves, when mature, possess pinnate venation more or
less conspicuously anastomose, the venation in the first stages of
the leaf is free.

*Camptosorus rhizophyllus, Anchistea Virginica, Lorinseria areolata, and Onoclea
sensibilis.

Development of the Fern Leaf 1 9

In the leaf with pinnate anastomose venation, the incisions by
means of which segments are formed occur, as in the leaf with
pinnate free venation, between the primary branches of the leaf's
midveins, and the midveins of each of these segments start, as
in the latter leaf, from the primary branch, as a base, contained
within the segment.

In Fig. 5 is shown the section of a leaf with pinnate anasto-
mose venation in which segments have begun to form, with the
midveins of these segments
not yet evident. In Fig. 6
is shown a longitudinal sec-
tion of the segment of a leaf
with similar venation, partly

FIG. 5.

FIG. 6.

formed segments on one side of the mid vein, and the midveins
of these segments evident.

In the leaves with free flabellate venation, each simple leaf-
blade and each segment of each compound leaf-blade is entered
at base by a vein which, instead of forming a mid vein, either
forks once or is dissipated into forking veinlets: if the latter,
the successive veinlets, excepting the two first, which are formed
by the forking of the primary vein, are formed by the forking of
the veinlets preceding them.

Each incision subdividing the simple blade or segment of a

20

Development of the Fern Leaf

leaf with flabellate free venation into segments, occurs between
the two vein-branches formed by the first forking of the vein
entering the blade or segment. Each new segment thus con-
tains one of these branches, with its ramifications, if any. If no
ramifications exist, some may appear afterward, or, if some exist,
more. There are also cases in which, coincidently with the fork-
ing of the vein that enters each segment, and before either of the
two branches formed by this forking fork, an incision subdivid-
ing that segment into segments occurs. The latter cases are
analogous to those in which the venation of the leaf is pinnate
and incisions occur between the primary branches of the leaf's

midveins coincidently with the
formation of these branches
and while they are still simple;

FIG. 7.

FIG. 8.

and in both sorts of cases the leaf-blade appears to be made up
of lobes containing each a simple vein.*

In Figs. 7 and 8, segments of a leaf with free flabellate
venation are shown in different stages of subdivision. In Fig. 7 a
the beginning of the incision by means of which the segment is
to subdivide is barely indicated. In Fig. 8 b the incision is pro-
nounced. In Fig. jcde the incision has extended nearly far
enough to render one (e) of the two new segments distinct, and

* See page 16.

Development of the Fern Leaf 2 1

the other (d) of these two segments has begun to subdivide into
segments.

Since, when a simple leaf or segment of a leaf with free fla-
bellate venation subdivides into segments, the incision occurs be-
tween the two vein-branches formed by the fork of the vein that
enters the simple leaf or segment, and since each of these branches
thus becomes the vein entering one of the two new segments, this
branch's starting-point — namely, the apex (point of forking) of
the vein that entered the original simple leaf or segment — may
be considered the starting-point or base of the segment this
branch enters.* Any two segments formed by the subdividing
of a simple leaf or simple segment of a leaf with free flabellate
venation are thus situated at the apex (point of forking) of the
vein that entered the original simple leaf or segment. Hence, if
the part of the original simple leaf or segment that contains this
vein becomes sufficiently attenuate it will constitute a stalk bear-
ing two segments at apex. If, then, either one of the latter seg-
ments, which may be designated as a, becomes transformed in
like manner into a stalk with two segments at apex, and the
other, which may be designated as 6, remains undivided, the
latter stalk will have the same starting-point as b, since it is
formed of the lower part of a, and since a and b had the same
starting-points. This stalk will, therefore, separate the pair of
segments at its apex from b by its length, which is the length of
the vein occupying it, namely, the vein that entered a. This
stalk will thus constitute a rachis. If b was the left one of the

* The end of the incision by means of which the two segments are formed cannot
be held to determine the starting-points of these segments, for it varies in position in
different stages of the segments' development.

22 Development of the Fern Leaf

segments a and b, b obviously will now be at the left side of the
base of this rachis if the right one, at the right side.

If, now, of the two segments at the apex of this rachis, which
may be designated as c and d, one (c) becomes transformed into
a stalk with two segments at apex, in the same manner as the
original simple leaf or segment and as a was transformed, and
the other (d) remains undivided, the latter stalk will constitute
a second section of rachis which will separate the latter pair of
segments from d, while the first section of rachis will still separate
d from a. If d were the left one of the segments c and d, d will
now be at the left side of the base of this second section of rachis;
if the right one, at the right side. D and b may, therefore, be
either on the same side of the rachis composed of the two sections
or on opposite sides. If on opposite sides, they will be alternate,
since they will be separated by the length of a vein. This vein
may, however, be so short as to be imperceptible to the naked
eye, in which case they will appear opposite.

If, instead of the segments subdividing in the above-described
order, the original simple leaf-blade or segment becomes trans-
formed into a stalk with two segments at apex, in the manner
above described (i.e., by subdividing into segments and becoming
attenuate below these segments), and each of the latter segments
becomes transformed likewise into a stalk with two segments at
apex, a dichotomous rachis with two segments at each end of its
fork will result; for this reason. The starting-points of the two
segments formed by the subdividing of the original simple leaf-
blade or segment will also be the apex of the stalk composed of
the lower part of the latter; hence, when the lower parts of these
segments shall have become stalks, the starting-points of the latter

Development of the Fern Leaf 23

stalks will be the apex of the former stalk, and the three stalks
will thus constitute a dichotomous rachis.

It is thus apparent that each section of rachis in a leaf with
free flabellate venation consists of the part of some segment sub-
divided into segments that contained the vein entering the seg-
ment, and which has become attenuated. This attenuation of
this part of the segment that becomes the section of rachis may
take place before, during, or after the subdividing of the segment
into segments. If before, the segment, until it. subdivides into
segments, will appear merely stalked, and if it be one of the two
terminating a rachis or petiole of a leaf, will appear raised above
the other by its stalk.

It is also apparent that whether the rachises of the leaf with
free flabellate venation are simple, forked, or otherwise com-
pound, and whether they bear segments on one or both sides, as
well as at apex, or at apex only, depends upon which of the leaf's
segments subdivide into segments and become attenuate below
these segments in the course of the leaf's development.

There are certain cases in which the compound or partly
compound leaf with free flabellate venation may resemble or be
indistinguishable from that with free pinnate venation. For
example :

(i) When in the flabellate-veined leaf segments are borne on
both sides of the rachises, and attenuation of the parts of segments
of which the rachises are composed has not been very complete,
so that a small amount of leafy tissue forming a wing remains
about the vein each of these parts contains, this leaf may re-
semble or may be indistinguishable from the pinnate-veined leaf
in which the incisions between the primary branches of the mid-

24 Development of the Fern Leaf

veins (by means of which segments are formed), have not quite
reached the midveins.

(2) When in the flabellate- veined leaf one of the two segments
formed by the subdividing of a simple leaf or segment subdivides
into segments coincidently with the occurrence of the incision by
means of which it is formed, and before the lower part of it has
become transformed by attenuation into a rachis, the same effect
may be produced as when, in the pinnate- veined leaf, two of the
incisions between the primary branches of the midvein of a
simple leaf-blade or segment occur above the two lowest primary
branches (one on each side of the midvein), before other such
incisions occur and while the midvein is in an incipient state.

(3) When, in the pinnate- veined leaf, one of the incisions
between the primary branches of the midvein of the simple leaf-
blade or segment occurs above the lowest primary branch on
one side of the midvein before any other such incision occurs, and
while the midvein is in an incipient state, this leaf-blade or seg-
ment may appear to be cut more or less vertically in two, and
thus like the simple leaf-blade or segment of the flabellate- veined
leaf which is subdividing into two segments.

In the leaf with unilateral venation, each segment of the leaf
is entered at base by a vein which extends through it at one side,
in the form of a unilateral midvein bearing branches on one side
only. These branches, each of which has its base attached to the
midvein, are the midvein's primary branches, and may be simple
or bear branches.

In Fig. 9 is shown the segment of such a leaf.

I have been able to study the development of the leaf with
unilateral venation in one plant only, namely, A diantum pedatum.
The development of the venation of the leaf of this plant, and

Development of the Fern Leaf 25

the occurrence of incisions, etc., in the leaf, are discussed in the
chapter on Adiantum pedatum* and so need only be touched
upon here.

In the leaf of this species, incisions occur between most or all
of the primary branches of the midveins. These incisions, with
the exception of the basal one, do not deepen sufficiently to render
the segments formed by them either distinct or nearly so. The

FIG. 9.

basal incision occasionally deepens sufficiently to render the basal
one of these segments, distinct, and in this way new segments are
added to the leaf. The basal primary branch of the midvein
of the segment from which the basal segment is separated is thus
included in the new segment and develops into its unilateral mid-
vein. This development may become evident either before or
after the basal segment becomes separated, and similar develop-
ment of the midvein's basal primary branch is sometimes seen
in segments from which the basal segment never becomes sepa-
rated.

It will be seen that the ultimate form of the compound fern
leaf depends chiefly upon the manner in which the leaf-blade,
when first formed, and such of its successive segments as do so,
subdivide into segments, upon which, if any, of the segments

* See pages 35-37.

26 Development of the Fern Leaf

subdivide, and upon the extent to which this subdivision is car-
ried, in the course of the leaf's development.

Instances sometimes occur in which some part of a species'
leaf that normally is undivided becomes subdivided into seg-
ments, and one, or repeated, series of segments may arise from
these. Such development of the leaf may be characterized as
monstrous. It sometimes produces most beautiful crested and
ruffled effects in the leaf. Many so-called "varieties" are based
upon leaves that are only monstrously developed.

Monstrous development may occur in any part of a leaf, and
in one leaf only, or in more or in all of a plant's leaves. When
it occurs in more than one of a plant's leaves, it often varies in
degree in the different leaves, although it may affect similar parts
in these leaves.

When the monstrously developed leaf is fertile, monstrous
development similar to that which appears in it often appears in
the leaves of any plants which may spring from its spores.

It is sometimes difficult to distinguish between monstrous de-
velopment and normal development carried further than usual.
The latter, however, is to be looked for in especially luxuriant,
mature, fertile plants, and produces effects that appear the logical
sequel to all that has gone before in the way of leaf -development ;
while the former, due to unknown causes, is often correlated with
partial or complete sterility of the leaf, often produces freakish
effects, and is apt to be visible from the first appearance of leaves
on the plant.

CHAPTER II
WALL-RUE

Belvisia ruta-muraria.

Rootstock creeping, short, chaffy: scales minute, strongly
striate-reticulate in blackish-brown, linear or linear-lanceolate,
acuminate, entire or ciliate: leaves fascicled at end of rootstock:
roots springing from bases of petioles, one to each petiole.

Leaves evergreen.

Petioles two to three inches long, usually as long as or longer
than blades, more or less grooved on face, otherwise rounded or
above faintly grooved on sides; at base deep brown or dark
purple, slightly rigid, glandular, chaffless or bearing at base a
few scales like those of rootstock; above green, herbaceous,
glabrous, glands large, grayish, globose, unicellular: fibrovas-
cular bundle solitary, flattened-cylindrical.

Blades two-fifths of an inch to two and one-third inches long,
ovate or ovate-deltoid, below bi-tri-pinnate, above once pinnate:
pinnae alternate, oblique to rachis, the compound stalked : ultimate
divisions alternate, one-twelfth to two-fifths of an inch long,
roundish-obovate to cuneate-rhomboid or cuneiform, at base
entire, upper margin crenate or dentate or incised or in young
plants undulate : rachises green, channelled on face : surfaces
glabrous: color bluish-green or olive: texture coriaceous. or sub-
coriaceous.

28 Wall-Rue

Venation flabellate, free or with occasional areolae: veins
repeatedly forked.

Sori short-oblong to linear, borne on veins near and opening
toward centres of ultimate segments of leaf: indusia whitish,
delicately membranous, ciliate-erose.

Spores ovoid-bean-shaped, minutely roughened.

Habitat. Seams, pockets, and ledges of calcareous rock:
usually exposed to the sun or in partial shade. Growing in tufts.

Range. Vermont, southern Ontario, and Michigan, south to
Alabama and Missouri.

Asplenium ruta-muraria. Linnaeus, Species Plantarum, 1081. 1753.

THE leaf-blade of Belvisia ruta-muraria is at first simple
and more or less rounded, and somewhat truncate at base or
soon becoming so (PI. I, Figs, i a, 2 a, 30). It then develops
into a blade consisting of a single leaflet-bearing rachis, in the
following way.

A slight incision forms at the apex of the blade (Fig. 2 6), and
gradually deepens until the blade is cut into two leaflets (Fig. 3
c d c' d'}. One of the two remains, temporarily, undivided (Figs.
3 c', 4 c'). The other becomes at base elongate and narrow, form-
ing the beginning of a rachis, and divides above into two leaflets
(Figs. 3</', 4 a', 5 dd'\ as the simple leaf-blade divided. The rest
is repetition: one of every two leaflets formed remaining undi-
vided, and the other becoming transformed at base into an exten-
sion of the rachis and dividing above into two leaflets. Which of
the two leaflets remains undivided depends in each case upon
which of the two in the preceding case remained undivided: if
the left leaflet in the one case, the right leaflet remains undivided

Wall-Rue 29

in the following case, and vice versa. The leaflets remaining are
thus rendered alternate on the rachis.

Almost coincidently with the formation of this primary rachis,
similar development of leaflets upon it into secondary leaflet-
bearing rachises is begun (Figs. 5 e, 6 e, and 7 eg). This is some-
times followed by similar development of leaflets upon the sec-
ondary rachises into tertiary leaflet-bearing rachises (Figs. 9 h,
10 W).

It will be noted that in each instance development of the leaf-
lets of each rachis into leaflet-bearing rachises begins with the
leaflet lowest (first formed) on that rachis, and involves succes-
sively the leaflets above in the order in which they were formed;
and that likewise the formation of the tertiary rachises begins on
the lowest (first formed) secondary rachises, and involves suc-
cessively the secondary rachises above in the order in which they
were formed.

The venation is flabellate. In consequence,* each incision
that transforms a leaflet or simple leaf-blade into two leaflets
occurs between the vein-branches formed by the first forking of
the vein that enters that leaflet or leaf -blade. Each branch thus
becomes the vein entering one of the new leaflets; and the first
forking of the one entering the leaflet that is in turn to subdivide
forms the two branches between which the incision is to occur,
while the part of it below its first fork is contained in that leaf-
let's base, which finally becomes elongate and forms a section of
rachis. Sometimes the subdivision of a new leaflet takes place
before it becomes fully separated from the old one, giving the old
the appearance of being cut into three.

When a leaflet on one rachis subdivides in the beginning of

* See Chapter I, pp. 19 and 20.

30 Wall- Rue

the formation of another rachis, the base of this leaflet, contain-
ing the part of the vein that enters the leaflet below the first fork-
ing of that vein, becomes elongate and forms the part of the new
rachis between its first leaflet and the old rachis.

The part in general taken by the venation in the leaf-develop-
ment will be more readily understood by studying PI. I, Fig. 2.

Many of the leaflets of the leaves of the older plants are more
or less incised between the marginal veinlets. This incision, to
which is due the peculiar toothed appearance seen so often in
this fern's leaves, is not to be confused with the incision described
above, employed in the leaf -development.

The plants bear sporangia when very young. The bifoliate
leaf is sometimes fertile.

A. ruta-muraria has been included in the genus Asplenium
by nearly all pteridologists. Newman, however, in 1844, sepa-
rated it from Asplenium, to form, together with A. septentrionale
and A. germanicum, a genus which he named Amesium. But
A. septentrionale had already stood as the type of a genus of
Mirbel's. * The affinity of A . ruta-muraria with A . septentrionale
appears very marked, especially on comparing the leaf -devel-
opment of the two species, and, taking into consideration the
flabellate venation and other peculiarities which characterize
these two species, they appear sufficiently distinct to warrant
restoring Mirbel's genus Belvisia and including A. ruta-muraria
in it.

* Belvisia Mirb. in Lam. & Mirb. Hist. Nat. Veg. 3: 405. 1802.

EXPLANATION OF THE PLATE.

PLATE I. — WALL-RUE. Belvisia ruta-muraria. i-io. Plants and leaves
in different stages of development, i. Young plant attached to prothallus.
9,10. Mature leaves, n. Fertile leaf, X 2^.

N

c.

-c'

a

••e

•d

e

-

.-e

h

PLATE I.—

, a

t

1

..a

••• h'

CHAPTER III
MAIDENHAIR

Adiantum pedatum.

Rootstock wide-creeping, branching, brown, slender, clothed
with numerous small, brown, glossy, imbricated, oblong, acu-
minate, entire scales: leaves approximate, rising alternately
from right and left sides of rootstock: roots irregularly scat-
tered, springing from rootstock.

Leaves erect; sporophylls withering in autumn; sterile leaves
sometimes persisting into winter.

Petioles eight to eighteen inches long, slender, glossy, wiry,
dark-reddish-chestnut to purplish-ebeneous or ebeneous, slightly
angled at sides, convex at back, flattish-convex on face or fur-
rowed when dried; clothed at base with imbricated scales sim-
ilar to scales of rootstock, the uppermost two to three times
larger; scales above few, scattered, deciduous: fibrovascular
bundle solitary, at base of petiole U-shaped, becoming above
V-shaped in section.

Blades imperfectly circular, somewhat funnel-form in centre,
flattened toward edge, eight to eighteen inches broad, dichoto-
mous: rachises wiry, glossy, chestnut-brown to black, some-
times purplish, tapering; the halves of the primary rachis di-
verging at an acute angle, curving outward and upward and

34 Maidenhair

bearing at apex two pinnae and, except in very small leaves, on
upper side about two to twelve radiating pinnae interspersed
with single pinnules, a single pinnule also borne on rachis below
one of basal pinnae : pinnae lanceolate or linear-lanceolate or the
smaller oblong or suboval, obtuse, pinnate, the basal six to ten
inches long, the outer successively shorter: pinnules numerous,
two-fifths of an inch to one inch long, alternate, stalked, oblong or
oblong deltoid, the apical cuneate, the lower mostly becoming cu-
neate or transversely oblong, attached at acute lower corner, other
comers rounded ; entire on sides next footstalk, otherwise dentate
and on upper side or both upper and outer sides cut into oblong
often oblique lobes; apical pinnules, and outermost basal pinnules
of outermost pinnae, sometimes bifid: surfaces glabrous; the
upper repelling water, bright green or darker; the lower paler;
texture elastic, membranaceous.

Venation conspicuous, free: principal vein of each pinnule
dividing at base of pinnule into two branches: in oblong or
deltoid-oblong pinnules, the outer branch forming a unilateral
midvein next pinnule's lower margin, bearing branches on upper
side; the inner branch appearing as basal primary branch of
the outer, little, if any, more complex than primary branch next
it: in cuneate or transversely oblong pinnules both branches
forming unilateral midveins, one each side of pinnule's footstalk,
next pinnule's margin, bearing branches on upper side : primary
branches of midvein three to four times forked at midvein's
base diminishing to once-forked or simple at midvein's apex,
pinnule's lobes each occupied by one.

Sori borne at apices of veinlets on under side of indusia:
indusia consisting of reflexed altered portions, chiefly ends of
lobes, of pinnule's upper margin, transversely oblong or linear

Maidenhair 35

or the smaller sublunulate, yellowish-brown, slightly striate; at
margin whitish, thin, membranaceous, somewhat erose or slightly
denticulate.

Spores spheroid-tetrahedral, the three radiating angles marked
with slender vittse or bands.

Habitat. Rich woods, shaded banks, etc.

Range. Nova Scotia to British Columbia, south to Georgia,
Mississippi, Arkansas, Kansas, Utah, and California. Also in
Alaska.

Adiantum pedatum. Linnaeus, Sp. PI. 1095. 1753.

THE petioles and rachises of Adiantum pedatum are dark-
colored in all stages of development. In the earliest stages
they are hair-like.

The leaf-blade is simple at first (PL II, Fig. i a, a). It
soon develops into a blade consisting of a single rachis leaf-
let-bearing at sides and apex (Figs. 2-6). First one and then
the other of the two basal leaflets on this rachis then develop
into a branch, which consists of a similar leaflet-bearing rachis
(Figs. 76, c; 86', c'). The outer basal leaflet (Fig. Sd) of the
first branch (Fig. 8 b') then develops likewise into a branch (PI.
Ill, Fig. qd'). In this way the earliest dichotomous leaf-blade is
formed (PI. Ill, Fig. 9). This may be said to consist of a di-
chotomous rachis (Fig. 9 e' o' jf) bearing two pinnae at each of
its two apices.

The leaflet that was formerly the inner basal leaflet g of the
branch b' in Fig. 8 (PI. II), becomes, when the outer basal leaflet
d in Fig. 8 develops into the branch d' in Fig. 9 (PI. Ill), the
leaflet g' on the section V o' of the dichotomous rachis e' o' }' in
Fig. 9, since e' o' in Fig. 9 corresponds to e o in Fig. 8. As no

36 Maidenhair

leaflet occurred on the part of the rachis o j in Fig. 8, no leaflet
is seen on the corresponding section o' j' in Fig. 9. This ex-
plains why, in mature leaves of A. pedatum, a leaflet is seen on
one side of the dichotomous rachis below the first (central) pinna
and not on the other.

The dichotomous leaf-blade (Fig. 9) having been formed, the
dichotomous rachis is prolonged and pinnae and pinnules are
added to its upper side by the development, repeated in successive
leaves, of the outer basal leaflet of the outermost pinna at each
end of the dichotomous rachis into a branch. For instance, by
the development of the outer basal leaflet h of the outermost
pinna i in Fig. 9 into a branch, Fig. 9 becomes, essentially, Fig.
10. The leaflet h in Fig. 9 becomes the outermost pinna hf in
Fig. 10, the part of the pinna i above the leaflet h in Fig. 9 be-
comes the pinna i' in Fig. 10, the part of the pinna i below the
leaflet h in Fig. 9 becomes the part /' /' of the dichotomous rachis
in Fig. 10, and the inner basal leaflet k of the pinna i in Fig. 9
becomes the leaflet k', on the dichotomous rachis in Fig. 10. It
is evident that if in Fig. 9 the inner basal leaflet k of the pinna i
had been higher on the stalk of that pinna than the outer basal
leaflet h, instead of lower, the corresponding leaflet in Fig. 10
would appear on the pinna i' instead of on the dichotomous
rachis. Since there seems to be no reason why the outer rather
than the inner basal leaflets of the outermost pinnae of the di-
chotomous leaves, or of the basal pinnae (bf, cf) of the leaf shown
in Fig. 8, should be the higher, we should expect to find in
some leaves of this plant, and do find, leaflets missing from the
dichotomous rachis that are present in others.

Fig. 1 1 represents a leaf in a later stage of development than
Fig. 10.

Maidenhair 37

Development of a leaflet into a branch is brought about in
the following way. An incision forms between the two vein-
branches formed by the first forking of the vein that enters the
leaflet, and cuts the leaflet into two leaflets. One of the two thus
formed remains, at least temporarily, undivided. The base of
the other leaflet becomes elongate, attenuate, and dark-colored,
forming the beginning of a rachis, and this leaflet, which may be
called the apical one, divides into two as the original leaflet divided,
the incision occurring, as in the latter, between the two vein-
branches formed by the first forking of the vein that enters the
leaflet. The rest is repetition, one of every two leaflets formed
remaining undivided, and the other becoming transformed at
base into a continuation of the rachis and dividing above into
two leaflets. Which of the two leaflets remains undivided de-
pends in each case upon which of the two remained undivided in
the preceding one: if the left leaflet in the one case, the right
leaflet remains undivided in the following case, and vice versa.
The leaflets remaining on the sides of the branch are thus ren-
dered alternate.*

The apical leaflets are cuneate. Most of the leaflets left on
the sides of the rachis lengthen at right angles to the rachis, be-
coming more or less oblong, although the lower ones, which may
lengthen in the opposite direction also, are apt to become more or
less cuneate.

In the earliest leaves the unilateral midveins of the leaflets
are little developed, sometimes barely developed beyond their
superior basal branches. As a result, the venation at this stage
of development can scarcely be called anything but flabellate.

* It will be noted that the development of leaflets into branches is here essentially
the same as in certain leaves with flabellate venation. See pages 21-22.

38 Maidenhair

A curious analogy exists between the development of the
venation and the development of the form of the leaf -blade. As, in
the course of development, each successive outermost pinna of
each half of the dichotomous rachis becomes forked (by the trans-
formation of its outer basal leaflet into a branch), the part below
the fork becoming a continuation of the dichotomous rachis, one
of the two parts above the fork a pinna upon that rachis, and the
other part the new outermost pinna ; so each successive outermost
veinlet of each unilateral mid vein becomes forked, the part
below the fork becoming a continuation of the unilateral midvein,
one of the two parts above the fork a primary branch upon that
midvein, and the other part the new outermost veinlet. In this
way the incipient unilateral midveins are developed and primary
branches are added to their upper sides.

In some leaflets, notably the apical and some of the lower,
the basal primary branch of the unilateral midveins of each is
developed in a similar way into a unilateral midvein, and the
two unilateral midveins taken together may be said to constitute
a dichotomous midvein with primary branches springing from
its upper side. The analogy between this and the plant's di-
chotomous rachis with branches springing from its upper side is
apparent. In those leaflets that possess only one unilateral mid-
vein, or one half of a dichotomous midvein, the latter may be
likened to one half of the dichotomous rachis. But here the
analogy ceases, for the branches that spring from the upper sides
of the midveins, unlike the branches that spring from the upper
side of the dichotomous rachis, fork repeatedly. They are less
complex in the early stages of leaf-development than in the
later.

Incisions, cutting the leaflets into shallow lobes, occur between

Maidenhair 39

the primary branches of the midveins.* By a deepening of the
one next the basal primary branch, which brings its base between
this branch and the mid vein itself, the incision described above,
that divides the leaflets into two in the development of the leaf,
is formed; since that incision occurs between the vein-branches
formed by the first forking of the vein that enters the leaflet, and
since the basal primary branch of a unilateral midvein and the
midvein itself represent those branches. This applies both to
those leaflets possessing only one midvein and to those possessing
two midveins, since in the latter case either of the two may be
regarded as the basal primary branch of the other.

The incisions between the primary branches of the midveins
suggest the lines along which future development, normal or
monstrous, of this plant's leaf may follow. The lobes which the
incisions form can be regarded as partly formed leaflets, and it
would not be surprising if at any time the incisions should deepen
sufficiently to render these leaflets distinct. It has been seen that
the basal incision already deepens at times (in the development
of the leaf's form), sufficiently to render the basal one of these
leaflets distinct.

* This is best seen in the sterile leaves. In the sporophylls an indusium occasionally
extends over the tops of several primary branches, so that no incisions occur between those
branches.

EXPLANATION OF THE PLATES.

PLATES II-III. — MAIDENHAIR. Adiantum pedatum. Plate II. — i.
Young plant attached to prothallus. 2-8. Young leaves in early stages of
development. Plate III. — 9-11. Leaves in later stages of development. 12.
Fertile leaflet of mature leaf, X 2^.

a

,t

^v

1

f

.b

PLATE II. — MAIDENHAIR

PLATE III

.1

1

CHAPTER IV
HART'S-TONGUE

Phyllitis scolopendrium.

Rootstock caudiciform, somewhat chaffy: scales hyaline, pale
brown, usually reticulate or striate-reticulate in reddish-brown,
lanceolate, acuminate, entire: leaves in a crown: roots spring-
ing singly or in clusters from bases of petioles or from root-
stock.

Leaves ascending, the larger drooping, eight inches to two
feet long, four-fifths of an inch to two and one-third inches
broad, usually evergreen unless unduly exposed to cold.*

Petioles two to six inches long, shorter than blades, toward
base brown, slightly turgid; above green; somewhat flattened
on three sides and two-ridged above, traces of groove on face,
or subterete, chaffy: scales pale brown, delicately reticulate in
brown or reddish-brown, lanceolate to narrowly elongate-linear
from a broader base, acuminate, entire or below ciliate, those
near base of petiole broadest; fibrovascular bundles two, curved
and finally forming an X.

Blades lanceolate or oblong-lanceolate or linear-lanceolate,
acute or obtuse, cordate or auricled at base, entire or undulate
or abnormally variously incised, finely and more or less ob-

* W. R. Maxon.

CHAPTER IV
HART'S-TONGUE

Phyllitis scolopendrium.

Rootstock caudiciform, somewhat chaffy: scales hyaline, pale
brown, usually reticulate or striate-reticulate in reddish-brown,
lanceolate, acuminate, entire: leaves in a crown: roots spring-
ing singly or in clusters from bases of petioles or from root-
stock.

Leaves ascending, the larger drooping, eight inches to two
feet long, four-fifths of an inch to two and one-third inches
broad, usually evergreen unless unduly exposed to cold.*

Petioles two to six inches long, shorter than blades, toward
base brown, slightly turgid; above green; somewhat flattened
on three sides and two-ridged above, traces of groove on face,
or subterete, chaffy : scales pale brown, delicately reticulate in
brown or reddish-brown, lanceolate to narrowly elongate-linear
from a broader base, acuminate, entire or below ciliate, those
near base of petiole broadest; fibrovascular bundles two, curved
and finally forming an X.

Blades lanceolate or oblong-lanceolate or linear-lanceolate,
acute or obtuse, cordate or auricled at base, entire or undulate
or abnormally variously incised, finely and more or less ob-

* W. R. Maxon.

44 Hart's-Tongue

scurely chaffy or paleaceous, especially below along midrib:
scales colorless or bronze-colored, often with bronze-colored
cross- barred centres, narrowly lanceolate or linear-acuminate:
color bright or deeper green : texture subcoriaceous.

Venation pinnate, free or with occasional areolae: primary
branches of midrib, excepting the basal, once to three times forked
or in apex of blade simple; the basal more complex, repeatedly
branched.

Sori linear, contiguous and faced in pairs on adjoining veins,
commonly one sorus of each pair extending along more or less
of the inferior veins of a primary branch of midrib and the other
similarly borne on the superior veins of the next adjoining pri-
mary branch, occasionally both on veins of the same primary
branch: the opposed indusia at first flat and overlapping, entire
or subentire.

Spores reticulate, verrucose.

Habitat, Crevices of limestone rocks or earth upon lime-
stone. On hummocks in dark, moist, rocky woods, on talus,
and in or about the mouth of open chasms, particularly in shaded
cold places near water.*

Range. Central New York, Tennessee, New Brunswick,
Grey and Simcoe counties, Ontario. Also in Alaska (?).

Phyllitis scolopmdrium (L.). Newman, Hist. British Ferns, ed. 2, 10.
1844.

Asplenium scolopendrium. Linnaeus, Sp. PI., 1079. 1753.
Scolopendrium vulgare. J. E. Smith, Me"m. Acad. Roy. Sci., Turin, 5: 421.

Scolopendriu mscolopendrium. Karsten, Deutsch Fl., ed. i. 278. 1880-83.
* W. R. Maxon. See Fernwort Papers, 30-46. 1900.

Hart's-Tongue 45

IN the development of the leaf of Phyllitis scolopendrium the
blade assumes successively the following forms: spatulate; spatu-
late-oval or suborbicular; suborbicular or roundish-ovate or
ovate-oblong, becoming cordate; ligulate-cordate ; and oblong-
lanceolate or lanceolate or linear-lanceolate with cordate or auric-
ulate base.

The spatulate leaf contains either a simple vein or an incipi-
ent midvein which does not extend beyond two basal primary
branches. The midvein is evident in succeeding leaves. It
gradually lengthens and sends out successive primary branches,
and is finally contained in a midrib.

The basal primary branches of the midvein may be once
forked or even occasionally simple at first. They vary, but are
mostly more complex than the primary branches above them.
As development of the blade progresses they branch more and
more, and in the mature leaves are markedly complex.

The primary branches above the basal mostly vary at first
from simple to once forked, but gradually become more com-
plex. In the mature leaves they vary from once to three times
forked, excepting the extreme uppermost, which, appearing later
than those below, sometimes do not develop beyond the simple
stage.

The veinlets are mostly clubbed at apex. They end near the
leaf's margin: the veinless border is often pronounced.

Occasional areolae occur in the mature leaves. I have seen
only one areole, near the midvein of a very small leaf, in the
young leaves.

At first the leaf-blade is decurrent on the petiole— so much
so in the narrower of the spatulate leaves that the petiole resem-
bles a winged midvein.

EXPLANATION OF THE PLATE.

PLATE IV. — HART'S-TONGUE. Phyllitis scolopendrium. 1-6. Young leaves
and plants in different stages of development, i. Plant attached to prothal-
lus. 7. Mature fertile leaf . 8. Section of fertile leaf, X2$.

-"

PLATE IV.—

f

^- 8

r's-ToNGUE

CHAPTER V

POLYPODY

Polypodium vulgare.

Rootstock slender, creeping, branching, brown or, at tips,
green, chaffy: scales numerous, small, brown; under a lens
yellow or orange, or margins subcolorless, the centre often
banded lengthwise in yellow or orange or reddish-orange-brown;
ovate or lanceolate, acuminate, cordate* and often dilated at
base, ciliate-erose : leaves approximate, borne alternately on
right and left of top of rootstock, articulated to rootstock: roots
springing from sides and base of rootstock, paleaceous.

Leaves ascending or suberect, four and one-half to sixteen
inches long, two-fifths of an inch to four and two-fifths inches
broad, evergreen, not prostrated in winter; in icy or dry weather
drooping forward, the segments curving horizontally and becoming
connivent over face of blade.

Petioles shorter to longer than blades, green or, when dried,
greenish-stramineous, on face convex or below flattened or
slightly hollowed, at back convex, on sides narrowly winged or
below angled, or at extreme base subterete, glabrous or bearing

* D. C. Eaton says "scales peltately attached," but I find a sinus leading from the
base to the point of attachment. An overlapping of the sides of this sinus often makes
the scales appear peltately attached.

50 Polypody

an occasional scale: scales next rootstock similar to those of
rootstock; those above pale brown, small, lanceolate or linear
or oblong, pointed, subciliate: fibrovascular bundles three to
four in base of petiole, the two anterior largest, uniting higher
up into one wedge-shaped in section or roundish and furrowed
on face.

Blades ovate-oblong or narrowly oblong or rarely lanceolate-
deltoid, pinnatifid or divided, gradually or abruptly narrowing
at apex; apex crenate or serrate or at base pinnatifid or at tip
undulate, obtuse or acute or acuminate, often elongate: seg-
ments about ten to twenty-three pairs, alternate or opposite,
mostly separated by acute or rounded sinuses, oblong or oblong-
linear or oblong-lanceolate, usually obtuse, rarely acute or acumi-
nate, usually undulate or obscurely serrulate or crenate, rarely and
abnormally coarsely serrate or variously lobed or pinnatifid: a
few minute, pale brown or partly colorless, hyaline, linear or ob-
long, acuminate, ciliate or subciliate scales occasionally borne on
under surface along rachis and midveins of segments, upper
surface glabrous or an occasional scale along rachis: rachis
green or greenish-stramineous, convex on face and back: color
otherwise olive-green, the under surface pale: texture subcori-
aceous.

Venation pinnate, wholly free or with occasional areolae:
primary branches of midveins of leaf's segments commonly
once-forked or at apex simple with two simple branches below,
the lowest branch on upper side sometimes, especially in large
segments, bearing a few simple or once-forked branches or in
apices of segments simple: apices of veinlets dilated, oval or
roundish, visible as straw-colored spots on face of leaf.

Sori round, borne singly on simple superior basal branches

Polypody 5 1

of primary branches of midveins of leaf's segments and apex,
commonly covering, sometimes below, apex of veinlet, often
becoming confluent.

Spores rather large, yellowish, oblong-reniform, minutely
areolated or reticulated, a single vitta or band along the con-
cave side.

Habitat. Flat or slightly sloping surfaces of rocks, wood-
land banks, stone walls, etc.

Range. Labrador and Newfoundland to Georgia, Alabama,
Missouri, Manitoba, and Keewatin. Probably has a wider
range toward the northwest.

Poly podium vulgar -e. Linnaeus, Species Plantarurr, 1085. 1753.

THE young leaves of Polypodium vulgare described here have
been mostly taken from offshoots of rootstocks of the older
plants: young plants attached to prothalli have not been seen.

The forms of the leaf-blade at different stages of development
may be seen from Plates V, VI, and VII.

Small notches, often obscure, occur between the primary
branches of the leaf's midveins and often between the veinlets
as well. By a deepening of the notches between the primary
branches of the primary midvein, the leaf's primary and, nor-
mally, only segments are formed. Almost, if not quite, coinci-
dently with this deepening, the section of leaf that goes to form
the segment lengthens at right angles or obliquely to the primary
midvein. The segments begin to form at the base of the leaf-
blade, and segment after segment are successively separated from
the part of the blade above, which continually lengthens at
apex. To a marked lengthening of the segments below the leaf's
apical section before the segments forming next above them have

5 2 Polypody

become especially lengthened, or perhaps more than mere lobes,
is due the abruptly narrowed appearance of the leaf-blade at
apex, common in this fern's leaves.

The blade at first is obtuse at apex, but as it grows large and
long it becomes acute or acuminate. Sometimes, although rarely,
the segments also become acute or acuminate. Acute or acuminate
apices in the segments are often correlated with monstrous de-
velopment of the leaf, but occur also in leaves otherwise typical,
particularly in unusually large ones. Their occurrence in the
latter leaves is in accordance with a tendency, common in many
ferns with pinnate venation, to lengthen and point the leaf-blade
and its segments, as these enlarge in developing, and such leaves
are at best doubtfully abnormal, although undoubtedly unusual
in P. vulgare.

The primary branches of the leaf's primary midvein develop,
while the segments are forming, into the segments' midveins.
Their branches are usually simple in the young very small leaves.
In the large, or at least in the older leaves, these branches bear
branches, and when the segments become incised in monstrous
development of the leaf, often appear as well-defined midveins
in the segments' lobes.

The superior one of the two basal primary branches of the
primary branches of the leaf's midveins is usually lower but
sometimes higher than the inferior, and sometimes opposite it.

On a superior one each sorus is borne. What seems at first
an exception to this occurs sometimes near the leaf's apex,
where the primary midvein, emerging from the rachis, appears
as a midvein in the leaf's apical section, and the series of
son belonging to it consequently appear. Here the superior
basal primary branch of the midvein of some one of the leaf's

Polypody 53

segments sometimes is once-forked and bears a sorus at each of
its two apices. The presence of both these sori can, however, be
accounted for. The presence of the sorus on the veinlet nearest
the segment's mid vein is explained, if that veinlet is regarded
as the superior basal primary branch of the primary branch of
the segment's midvein. The presence of the sorus on the other
veinlet also is explained, if this veinlet is regarded as merely an
extension of the superior basal primary branch of the seg-
ment's midvein, and so (since the segment's midvein is a pri-
mary branch of the leaf's primary midvein), as a part of the
superior basal primary branch of a primary branch of the pri-
mary midvein. Occasionally the two veinlets become connivent
at apex, and the two sori coalesce, forming one, which is borne on
the veinlet' s connivent apices.

Sometimes occasional areolae occur in the leaf at various
stages of its development.

The veins are clubbed at apex and appear to pierce the face
of the leaf: their tips are visible as stramineous spots on the
leaf's upper surface at every stage of leaf -development.

The leaf often becomes monstrously developed. "Var. Cam-
bricum" Moore, and many other so-called varieties of this species,
are based upon monstrously developed forms of the leaf.

EXPLANATION OF THE PLATES.

PLATES V-VII. — POLYPODY. Polypodium vulgare. Plate V. — 1-6. Young
leaves and plants in early stages of development. Plate VI. — i, 2. Young
leaves in later stages of development, i. Leaf with epidermis removed,
showing venation. Plate VII. — i. Mature fertile leaf. 2. Fertile pinna,
X 2.

PLATE V. — POLYPODY

PLATE VI. — POLYPODY

.

f

CHAPTER VI
PURPLE CLIFF-BRAKE

Pellaea atropurpurea.

Rootstock creeping, short, stout, usually nodose, thickly
clothed with soft, lustrous, cinnamon or orange-colored or
whitish, hyaline, linear, acuminate, entire scales: leaves clus-
tered at apex of rootstock: roots springing from rootstock, some-
times paleaceous.

Leaves two and one-third to twenty inches long; ultimate
divisions persistent during winter, falling off in spring,* petioles
and rachises persistent.

Petioles two to six inches long or longer, wiry, purplish-
ebeneous to blackish-red, rigid, terete; at base slightly turgid,
bearing a few scales similar to scales of rootstock; above usually
paleaceous: fibrovascular bundle solitary, U-shaped.

Blades about two to six inches broad, oblong-lanceolate or
ovate, above once, below twice pinnate: pinnae alternate or
opposite : ultimate divisions three-tenths of an inch to two inches
long, two-fifths of an inch or less broad, alternate or opposite,
obtuse or obscurely mucronulate; at base cordate, truncate, or
obtuse, sessile to short-stalked ; the sterile oval or ovate ; the fertile
linear or linear-oblong or the smaller elliptical; the apical long-

* H. H. Swift.

58 Purple Cliff-Brake

est, often elongate, often connate at base with segment next
below on one or both sides: margins thin, whitish, crenulate,
and very minutely and obscurely denticulate: upper surface of
ultimate divisions deep bluish-green, glabrous, lower surface
pale, minutely paleaceous along midveins: texture coriaceous:
rachises and footstocks of ultimate divisions purplish-ebeneous
or blackish-red, usually paleaceous.

Venation pinnate, obscure, free or with occasional areolae:
primary branches of midveins once to three times or the basal
four times, those above the basal mostly twice forked.

Sori intramarginal on upper part of veins, becoming conflu-
ent laterally: indusia formed of reflexed margin of ultimate
divisions of leaf, continuous around sides and apex of division
or interrupted at apex: at margin minutely denticulate or undu-
late, often finely fluted.

Spores obscurely tetrahedral, or trivittate.

Habitat. Dry rocks, especially limestone, exposed to the sun
or partly shaded. Often near the tops of cliffs, projecting in
masses from cracks in the rock or growing in partly caked sand
on the ledges; or on surface rock on hillsides.

Range. Massachusetts, Vermont, and Ontario to British
Columbia and Mackenzie, south to Georgia, Mississippi, Texas,
Arizona, and California.

Pellxa atropurpurea-L.innxus-'Lmk, Fil. Sp. Hort. Berol. 59. 1841.
Pteris airopurpurea Linnaeus, Sp. PI. 1076. 1753-

THE young leaf-blade of Pellcea atropurpurea is simple and
roundish or reniform at first (PI. VIII, Fig. i). It then elon-
gates and two lobes develop, either simultaneously or succes-
sively, at its base (PI. VIII, Fig. 2-5). These lobes are the blade's

Purple Cliff-Brake 59

incipient basal primary pinnae. In Fig. 6 they are shown fully
separated from the part of the blade above them. In later leaves
additional pairs of primary pinnae are formed, and in time a
series of secondary pinnae (Pis. IX, X).

Each pinna becomes distinct from the part of the leaf beyond
it before its subdivision into segments, if occurring, is begun, and
nearly always before formation of any pinna beyond it is begun:
before or during the formation of the incision that renders the
pinna distinct from the part of the leaf beyond it, the part of the
leaf that is to form the pinna usually elongates in the direction that
the pinna's apex is to take. As a result, at any stage of the leaf's
development each of the leaf's ultimate divisions or apical sections,,
excepting the microscopic irregularity of the margins, either with
rare exceptions is entire (PI. X, a), or has merely a single, often
extended, lobe at base on one or each side (PI. XI, a), from which
it is sometimes partly separated by an incision (PI. X, c).

The venation is pinnate. The blade's primary mid vein is so
little developed in the earliest form of the blade that the venation
at this stage of development may be called pseudo-flabellate, but
this mid vein becomes evident while the blade is still simple.
A midvein is evident in all but occasional, very small, newly
formed, ultimate divisions of the later leaves. The two basal
primary branches of each midvein are usually much more com-
plex than the others. In the lobed leaf-sections one or each of
the two constitutes the venation of a lobe, according to whether
there is a lobe on one or on each side of the section. The develop-
ment of the branch into a midvein in the lobe is evident either
before or, if the lobe be very small, soon after the lobe has become
distinct from the leaf-section, and in any case before the lobe, as
a distinct pinna, becomes, if ever, lobed.

60 Purple Cliff-Brake

When the blade becomes fertile, its segments, if any, narrow,
and its margins recurve. It becomes fertile at a very early stage
of development; a tendency to recurve is sometimes visible in
the margin of the simple leaf -blade, although apparently no
sporangia appears at this stage.

EXPLANATION OF THE PLATES.

PLATES VIII-XI. — PURPLE CLIFF-BRAKE. Pellcea atropurpurea. Plate
VIII. — i. Young plant attached to prothallus. 2-5. Young leaves in early
stages of development. Plate IX. — i, 2. Young fertile leaves. Plate X. —
Mature highly developed sterile leaf. Plate XI. — i. Mature highly developed
fertile leaf. 2. Fertile pinnule, X 2\.

J*

PLATE VIII. — PURPLE CLIFF-BRAKE

PLATE IX. — PURPLE CLIFF-BRAKE

PLATE XI.—]

LE CLIFF-BRAKE

CHAPTER VII
NARROW-LEAVED SPLEENWORT

Asplenium angustifolium.

Rootstock creeping, light greenish-brown, brown in age, a
few, delicate, pale -brown, lanceolate-acuminate or broade,
entire or slightly toothed scales: leaves clustered near apex of
rootstock, springing from all sides of rootstock: roots numerous,
light brown, coarse, springing from rootstock and bases of pet-
ioles, scattered or fascicled.

Leaves twenty to thirty- six inches long, three to eight and
three-fifths inches broad, sensitive to frost, sporophylls usually
longer and narrower, with narrower pinnae, than sterile leaves.

Petioles shorter than blades, fleshy-herbaceous; at base brown,
turgid-compressed; above green or, when dried, greenish-stra-
mineous to bright stramineous often tinged with brown, narrow
and furrowed on face, at back and on sides broader and flat-
tish; bearing a few pale-brown scales: fibrovascular bundles
two; in base of petiole strap-shaped or roundish strap-shaped,
slightly furrowed on one or both sides; higher up more or less
furrowed on outer broad side, convex in centre of opposite side,
somewhat 3-shaped in section; in apex of petiole uniting into
one unevenly U-shaped in section.

Blades lanceolate, gradually or abruptly narrowed at apex,

64 Narrow-Leaved Spleenwort

pinnate: apex long-acuminate, undulate to crenate becoming
parted below: pinnae approximate or distant, alternate or oppo-
site, mostly very short-stalked or subsessile, at base truncate or
wedge-shaped or rounded or, at least in sterile leaves, slightly
cordate, linear-lanceolate, in sporophylls often somewhat falcate,
acuminate; the basal reduced, often oblong-lanceolate or oblong-
ovate or ovate and obtuse; the uppermost oblong-lanceolate or
ovate-lanceolate, acute to obtuse, often passing into obtuse some-
times orbicular segments; subentire to undulate or crenulate,
rarely slightly and coarsely crenate and at base cut, abnormally,
into lobes: margins obscurely hyaline, very minutely and ob-
scurely serrulate: rachis furrowed on face, very narrowly winged
above, greenish-stramineous to bright stramineous when dried:
lower surface, sometimes both surfaces, bearing a few obscure,
minute, chaffy hairs: color grass-green or darker: texture thin,
herbaceous.

Venation pinnate, free or with occasional areolae: primary
branches of pinnae's midveins mostly simple in apices of pinnae;
the basal usually the most complex, once to three times forked;
those between mostly once to twice forked.

Sori linear or oblong, or the smaller suboval ; borne singly on
primary branches, when these are simple of midveins of pinnae
and apex of blade, when they are compound extending along or
wholly upon their superior basal branches, or when latter are
compound sometimes extending along or in apex of blade wholly
upon the veinlets next midveins, opening toward midveins: in-
dusia arched, entire.

Spores ovoid, covered with anastomosing ridges.

Habitat. Rich soil in damp woods or ravines, sometimes
near calcareous rock. Often with Dryopleris Goldieana.

Narrow-Leaved Spleenwort 65

Range. Northern New England and southern Quebec to
Wisconsin, south to northern Georgia, Tennessee, and Missouri.

Asplenium angustifolium Michaux, Fl. Bor. Am. 265. 1803.

THE young leaves of Asplenium angustifolium are translucent
when dried. The venation can be seen distinctly by transmitted
light, and the development of the vascular system easily observed.

At first only one fibro vascular bundle is present in the leaf's
petiole : it may perhaps sometimes divide into two at the extreme
base of the petiole. Soon two are seen, which merge into one
some distance above the base. The mature petiole contains two,
which coalesce to form the leaf-blade's primary midvein.

The venation is pinnate. The translucence of the young leaf
reveals the fact that a pinna's midvein sometimes leaves the
midvein (fibrovascular bundle) from which it springs some
distance below the apparent node of the pinna.

The formation of the pinnae is gradual. The pinnae appear
first as small lobes, on the lower part of the leaf's apical section
in the older leaf and substantially at the leaf's apex in the younger.
New lobes begin to form above those previously formed while the
latter are separating to constitute pinnae. This will be seen from
Plate XIV, and it will also be seen that both the pinnae and the
leaf -blade itself are short and blunt at first, but gradually lengthen
and become pointed more and more.

In some leaves of this fern, collected in Vermont by Miss
Mary E. Bidwell,* there are small lobes on the lower parts of the
pinnae, indicating a tendency to produce secondary pinnae. Some
of the basal lobes in these leaves are distinct. This seems to be
a case of monstrous leaf-development. Spores from these leaves

* See Fern Bulletin, 8: 61. 1900.

66 Narrow-Leaved Spleen wort

have been sown and have produced plants with some normal
leaves and with other leaves showing, at a very early stage,
similar abnormal lobes.

In this fern, as in other Asplenii, the sori are borne on veins
that stand in certain relations to the midveins, each sorus opening
toward a mid vein. Some veins occur that stand in one of the
required relations to each of two midveins, and, as a result, two
sori (diplazioid sori) sometimes occur on these veins, one sorus
opening toward each midvein.*

Each sorus is borne on a midvein's primary branch, or on
this branch's superior basal branch, or on a veinlet of the latter
next the midvein. The only veins that stand in one of these
relations to each of two midveins, and, consequently, the only
veins on which diplazioid sori occur, are the upper basal primary
branches of the pinnae's midveins. These branches stand both
in the relation of primary branches to the pinnae's midveins and
(since the pinnae's midveins are primary branches of the leaf's
primary midvein), in the relation of superior basal primary
branches of primary branches to the leaf's primary midvein.
Diplazioid sori occur only on the upper part of the leaf, perhaps
for the reason that the leaf's primary midvein, while showing its
character as a midvein in that part of the leaf, apparently loses
it below by becoming merged or concealed in the rachis.

Whether the sori which go to form the diplazioid sori are
diplazioid for the whole or only for part of their length depends
upon how far they extend. One may extend farther along the
upper basal primary branch of the pinna's midvein than the
other. At the upper end of this vein, if it divide into two veinlets,

* For instances of the occurrence of diplazioid sori in other Asplenii, see pp. 72,
89, and 90.

Narrow-Leaved Spleenwort 67

the two sori may continue, in which case they will diverge, each
following the veinlet nearest the midvein toward which this
sorus opens, as that veinlet is the only one of the two that stands
in one of the required relations to that midvein. At the lower
end, the sorus that opens toward the pinna's midvein cannot
extend farther than that midvein, as no sorus in this fern extends
at base farther than the midvein toward which it opens, but the
other sorus may extend down the pinna's midvein to the leaf's
primary midvein, toward which this sorus opens. It will be seen
that only such parts of the sori are diplazioid as extend along the
same part or the whole of the upper basal primary branch of the
pinna's midvein.

EXPLANATION OF THE PLATES.

PLATES XII-XIV. — NARROW-LEAVED SPLEENWORT. Asplenium angusti-
folium. Plate XII.— i. Young plant attached to prothallus. 2-5. Young
leaves in early stages of development. Plate XIII. — Young leaf in later stage
of development. Plate XIV.— i. Mature sterile leaf. 2. Section of fertile
pinna of mature leaf, X 2^.

PLATE XII. — NARROW-LEAVED SPLEENWORT

PLATE XIII. — NARROW-LEAVED SPLEENWORT

PLATE XIV.— NAR

SEATED SPLEENWORT

CHAPTER VIII
MAIDENHAIR SPLEENWORT

Asplenium trichomanes.

Rootstock caudiciform, slender, branching, chaffy: scales
small, lance-linear, acuminate, entire or slightly ciliate, with
subopaque, madeira-red or topaz-colored centres, otherwise hya-
line or reticulate in similar color: leaves fascicled at rootstock's
apex: roots springing singly from junctures of petioles and
rootstock.

Leaves ascending or reclined, often in flattened tufts, two and
four-fifths to eight inches long, two-fifths to four-fifths of an inch
broad, imperfectly evergreen, the petioles and rachises more or less
persistent, the pinnae beginning to drop off in autumn.

Petioles four-fifths of an inch to four and one-third inches long,
purplish or chestnut-brown, glossy, below terete orsubterete; above
flattened or slightly furrowed on face, narrowly winged on sides,
wings light brown; bearing a few scales at base and sometimes
above; scales lanceolate or linear, otherwise similar to scales of
rootstock or subopaque centres reduced or lacking: fibrovas-
cular bundle solitary, roundish or on face flattish.

Blades linear, obtuse or short-acuminate, pinnate: apex
crenate, often lobed or pinnatifid at base: pinnae alternate or
opposite, approximate or the lower more distant, subsessile or

72 Maidenhair Spleenwort

the uppermost sessile, articulated at points of attachment; the
lower reduced, roundish-oblong or roundish-oval or reniform,
or roundish-fan-shaped with cuneate or truncate base; those
above roundish-oblong or oval, obliquely wedge- truncate at base,
inequilateral, sometimes auricled on upper side; except at base
somewhat crenate or sometimes more or less incised: surfaces
glabrous: rachis purplish-brown, glossy, flattened or slightly
convex on face, appearing furrowed from wings connecting
pinnae which are similar to and continuous with wings of petiole :
foot-stalks of pinnae purplish- brown : color otherwise deep green :
texture firmly membranaceous.

Venation pinnate, free: primary branches of pinnae's mid-
veins, excepting the basal, mostly once-forked or the outermost
simple, or a few bearing branches which are simple to twice
forked: superior or both basal primary branches of midveins
once to three times forked or bearing branches which are simple
or bear branches.

Sori oblong or linear, each borne on a midvein's primary
branch when this is simple, when it is compound extending along
or wholly upon its superior basal branch or extending along or
wholly upon a veinlet of the latter next the mid vein, opening
toward the midvein: indusia whitish, delicately membranous,
subentire or undulate or irregularly crenate.

Spores marked with anastomosing ridges or verrucose or
papillose with ridges reduced or lacking.

Habitat. Seams, pockets, and ledges of shaded cliffs, par-
ticularly limestone.

Range. Nova Scotia and eastern coast of Hudson Bay to
Alabama, Texas, and Arizona, northwestward to Oregon, British
Columbia, and Alaska.

Maidenhair Spleen wort 73

Asplenium trichomanes Linnaeus, Species Plantarum, 1080. 1753.

YOUNG plants of Asplenium trichomanes are apt to be con-
fused with those of A . platyneuron, but can be easily distinguished
by the dark petioles of the very young leaves.* The petiole is
partly or entirely green in the young plant's first leaf, but becomes
almost at once, in succeeding leaves, dark and lustrous, shading
from stramineous-brown to dark purplish-brown.

Narrow membranous wings on the sides of the petiole, and
of the rachis if there is one, are visible from a very early stage of
leaf-development, if not from the first. At first the leaf-blade is
roundish-spatulate, and contains a simple vein. It then becomes
spatulate and obscurely notched at apex, next obcordate, and
then cuneate-bilobed ; and the vein sends out two branches at
apex, each occupying one of the lobes. The leaf-blade then be-
comes slightly more complex, lobed, and crenate, and its primary
vein (midvein) develops somewhat beyond the two first primary
branches.

The parts of the leaf-blade that contain these two basal primary
branches then separate from the upper part of the leaf-blade
sufficiently to form two pinnae, while the part of the leaf-blade
remaining above them that contains the section of the leaf's
primary midvein between the latter 's first (basal) and second
pair of primary branches becomes elongate and attenuate, form-
ing a rachis, over which the dark color of the leaf's petiole spreads
quickly. Additional pairs of pinnae are added successively to the
leaf in a similar way; by parts of the leaf containing the pair of
primary branches of the leaf's primary midvein, next above the
last pair of pinnae previously formed, separating from the upper
part of the leaf sufficiently to form a pair of pinnae, while the part

* See page 71.

74 Maidenhair Spleenwort

of the leaf containing the section of primary midvein between
that pair of primary branches and the pair next above becomes a
section of rachis. The primary midvein thus becomes merged
in a rachis, remaining visible as a midvein in the leaf's apical section
only. While pinnae and primary branches of this midvein are
separating from the base of the apical section, this section and this
midvein lengthen at apex, the midvein sending out additional
primary branches, but this takes place slowly; the apical section,
therefore, is usually rather short. One or more pinnae are usually
to be seen in the process of forming on and of separating from it.

In the very young leaf the pinnae newly formed are often, like
the leaf -blade newly formed, obcordate, with their mid veins not
developed beyond two simple primary branches. Such pinnae
resemble the pinnae of Asplenium Clutei, Gilbert.* The various
forms of the early pinnae can be seen from Plate XV. As the leaf
develops, the pinnae lengthen and broaden, gradually assuming
their mature forms, their midveins lengthen and send out addi-
tional primary branches, and these midveins' primary branches
mostly become more or less complex.

The pinnae are usually crenately toothed or lobed, but, occa-
sionally, incised. The so-called "var. incisum" is based upon
monstrously developed sterile leaves with deeply incised pinnae.

* See Fern Bulletin, 8: 62-63. 1900.

EXPLANATION OF THE PLATE.

PLATE XV. — MAIDENHAIR SPLEENWORT. Asplenium trichomanes.
Young plant attached to prothallus. 2-5. Leaves in early stages of develop-
ment. 6. Small mature plant. 7. Large fertile mature leaf. 8. Section of
fertile leaf, X 2\.

PLATE XV. — MAIDENHAIR SPLEENWORT

CHAPTER IX
EBONY SPLEENWORT

Asplenium platyneuron.

Rootstock creeping, chaffy: scales strongly reticulate in red-
dish-brown on a colorless or pale-yellow ground, lanceolate or
rarely linear, acuminate, ciliate : leaves fascicled at apex of root-
stock: roots springing from rootstock or junctures of rootstock
and petioles.

Leaves more or less evergreen, sporophylls erect, six inches to
two feet long, up to four inches broad ; sterile leaves more or less
reclined, much shorter.

Petioles four-fifths of an inch to four inches long, bright
reddish or darker chestnut-brown to chestnut-ebeneous, some-
times tinged with green, a small light-colored spot, tawny in dried
leaves, at the extreme base, glossy, subterete, turgid at base,
bearing a few scales : scales at base of petiole lanceolate to linear,
similar otherwise to scales of rootstock, passing above into
obscure scattered palea commonly hyaline and colorless on sides
with dark opaque reddish cross-barred centres: fibrovascular
bundles two in base of petiole, roundish strap-shaped, uniting
above into one roundish in section.

Blades linear-oblanceolate or linear-lanceolate, pinnate, pin-
natifid below the serrate or crenate, acuminate or acute or

78 Ebony Spleenwort

obtuse apex: pinnae alternate or rarely two opposite, crowded
often imbricated in sterile leaves, approximate or sometimes
crowded in sporophylls; excepting sometimes the uppermost,
dilated at base and auricled on upper side or both sides, lanceo-
late or subfalcate or, especially the lower, oblong, the lowermost
often unequally roundish-deltoid, obtuse or subacute or acute,
subentire or undulate, or, especially the lower, slightly crenate,
or serrate or, sometimes, obliquely cleft or pinnatifid, the lobes
mostly serrate; beneath very obscurely, minutely and sparingly
paleaceous, upper surface similar or glabrous: rachis reddish
or light or dark chestnut-brown, glossy, terete or subterete below,
above more or less furrowed on face, sparingly and obscurely
paleaceous, palea similar to that of upper part of petiole ; color
of rachis in large leaves sometimes encroaching on under side of
midveins of pinnae: color otherwise olive green: texture firmly
membranaceous.

Venation pinnate, wholly free or with occasional areolae : pri-
mary branches of pinnae's midveins, excepting the two basal, com-
monly once forked or at apices of pinnae simple, or in highly
developed, especially in lobed or pinnatifid pinnae, often bearing
simple or once-forked branches and each forming a midvein of a
lobe or segment; superior basal primary branch bearing a few
simple or once-forked branches and forming midvein of superior
basal auricle ; inferior basal primary branch once-forked or sim-
ilar to superior one, forming midvein of inferior basal auricle
when this auricle is present.

Sori oblong or linear, borne on branches of pinnae's midveins
and often on branches of midveins of pinnae's auricles or other
lobes or segments; each sorus on a primary branch of the mid-
vein, partly below its superior basal branch, extending along or

Ebony Spleenwort 79

wholly upon latter branch or extending along the veinlet of the
latter (when one is present), next the midvein, opening toward
the midvein: indusia whitish, delicately membranous, the mar-
gin erose or slightly ciliate-erose.

Spores brown, covered with anastomosing ridges.

Habitat. Dry places exposed to the sun or partly shaded;
usually near or on rocks. In old fields and pastures, among
stones by the roadside, etc.

Range. Florida to Maine and southeastern Ontario, west to
Texas and Colorado.

Asplenium platyneuron (Linnaeus) Oakes; D. C. Eaton, Ferns N. Am.
i: 24. 1878.

Acrostichum platyneuros. Linnaeus, Sp. PL 1069. 1753.
A s plenum ebeneum. Aiton, Hort. Kew. 3: 462. 1789.

THE blade of the leaf first produced by the young plant of
Asplenium platyneuron is usually either obcordate, or bilobed
with each of the two lobes slightly bilobed. If the first, it con-
tains a once-forked vein; if the second, a twice-forked vein, each
of the four veinlets occupying one of the lobes. Another very
young leaf is trilobed. It contains a vein which is simple at
apex, occupying the central lobe, and which bears two simple
branches below, each occupying one of the lateral lobes. The
leaf-blade becomes next somewhat more complexly lobed and
its midvein develops farther. Pinnae are then gradually formed,
in the same manner as in A. trichomanes* In A. trichomanes,
however, the pinnae are often opposite, whereas in A . platyneuron
they are nearly always alternate.

The leaf's petiole is green at first but soon begins to change
color, although not, at least noticeably, as soon as in A. tricho-

* See page 65.

80 Ebony Spleen wort

manes. The color that replaces the green appears first at the
petiole's base and spreads upward, involves in time the entire
rachis, and, occasionally, in the larger leaves, encroaches also on
the under surface of the pinnae, along the midveins. It is straw-
color at first, but gradually becomes chestnut-brown or darker,
finally shading from brown to ebony and, occasionally, tinged
with green.

Auricles at the bases of the pinnae are absent in the first early
stages of the leaf's development, but a tendency toward especial
development at the places where they are to appear later is early
noticeable. For instance, in many of the pinnae of very young
leaves the midvein's superior basal primary branch, which later
forms the midvein of the superior auricle, is once forked, while the
other primary branches are simple. The auricles gradually
form as the leaf develops, sometimes at the inferior sides of the
pinnae as well as at the superior. They are in reality incipient
secondary segments of the leaf.

Although the leaf-blade's margin is sometimes subentire or
merely undulate, a greater or less degree of incision between the
primary branches of the leaf's midveins, or at least a tendency to
such incision, is noticeable in all stages of the leaf. It is obvi-
ously carried to its fullest extent in the production of the pinnae.
In the pinnae themselves it is commonly shown merely by serra-
tion or crenation or undulation of the margin, but sometimes it
is carried far enough to render the pinnae cleft, more or less
deeply, into segments.

The so-called " var. serratum" Gray is based upon leaves
with such cleft pinnae. These leaves are not uncommon in
large, luxuriant, fertile plants, and represent, apparently, the
height of normal development of this fern's leaf. They are

Ebony Spleenwort 8 1

somewhat analogous to the highly developed leaves in Polystichum
acrostichoides.

The cleft pinnae are mostly unusually long, and commonly
occur in the more central part of the leaf -blade, which is, as a
rule, the most highly developed part of any mature leaf of this
fern. The primary branches of the pinnae's midveins are mostly
more complex in the cleft pinnae than in the others, excepting
those in the basal auricles of the latter, and constitute the seg-
ment's midveins. Series of sori occur along these midveins as
well as along the pinnae's midveins. In the uncleft pinnae series
of sori occur only along the pinnae's midveins and the auricles'
midveins. The auricles, which, as already stated, are incipient
segments, become basal segments in the cleft pinnae.

In this fern, as in A, angusti folium* diplazioid sori, or dipla-
zioid parts of sori, sometimes occur on veins that are both primary
branches of one midvein and superior basal primary branches of
primary branches of another.

In addition to the incision described above, employed in the
leaf's development, slight incision, or a tendency to slight incision,
between the leaf's ultimate veinlets is often noticeable in the leaf
at various stages. When present it adds to the unevenness of the
leaf -blade's margin, and in highly developed leaves causes the
pinnae's segments to appear toothed.

"Var. Hortonae" Davenport is based upon monstrous leaves
in which incision occurs in an extreme degree and is correlated,
so far as known, with total sterility of the leaf.

* See page 60.

EXPLANATION OF THE PLATES.

PLATES XVI, XVII. — EBONY SPLEENWORT. Asplenium platyneuron.
Plate XVI. — i. Young plant attached to prothallus. 4. Slightly older plant.
2-1 1. Young leaves in different stages of development. Plate XVII. — i.
Mature fertile plant, slightly reduced. 2. Section of highly developed mature
fertile leaf, slightly reduced. 3. Fertile pinna of less highly developed mature
leaf, X if.

11

8

PLATE XVI. — EBONY SPLEENWORT

c

is

55
H
H
J
i-
CO

CHAPTER X

\

CHRISTMAS FERN

Polystichum acrostichoides.

Rootstock creeping, chaffy: scales pale brown, lanceolate or
ovate, acuminate, slightly ciliate: leaves clustered at apex of
rootstock: roots springing from rootstock or extreme bases of
petioles.

Leaves ascending, five to twenty-seven inches long, two and
four-fifths to four and four-fifths inches broad, imperfectly ever-
green; in autumn prostrated, the fertile parts of sporophylls
usually withering.

Petioles shorter than blades, two to six and two-fifths inches
long, toward base dark, often reddish or lighter brown, above
green, somewhat flattened or furrowed on face, turgid at base,
chaffy: scales numerous, pale brown, ovate or lanceolate, acu-
minate, ciliate: fibrovascular bundles four or five; the two
anterior largest, ovate-wedge-shaped or suboval in section, or
slightly hollowed on one or both sides; the others ellipsoidal or
roundish in section.

Blades rigid, lanceolate, pinnate; apex pinnatifid, becoming
serrate or serrulate at tip, subacute or acute or acuminate : pinnae
mostly approximate or in sporophylls distant, alternate or oppo-
site, mostly subsessile or very short-stalked, obtuse or acute or

86 Christmas Fern

sometimes short-acuminate, linear-lanceolate or oblong-lanceo-
late, often somewhat falcate, half-halberd-shaped at base, occa-
sionally serrate or obliquely incised or pinnately parted into oval
or ellipsoidal or roundish -oblong sometimes distant segments,
which are often auricled on the upper side, only upper pinnae of
sporophylls, or in sporophylls with cleft pinnae the tips or more
of the lower pinnae also, soriferous; soriferous parts of blade
somewhat contracted: margins serrulate with appressed spinu-
lose teeth: rachis chaffy with pale brown, lanceolate or linear or
sometimes ovate, acuminate, ciliate scales: lower surface more or
less paleaceous, especially along midveins, the upper somewhat
so : color deep, lustrous green : texture subcoriaceous.

Venation pinnate, free or with occasional areolae: primary
branches of pinnae's midveins mostly simple at apex with two
simple alternate branches below, the basal one on upper side;
or bearing a few branches which are commonly simple or, in basal
lobes of pinnae, once-forked or at apex simple with two simple
branches below: primary branches of midveins of cleft pinnae
more complex; in pinnatifid pinnae constituting midveins of
segments, their branches simple or once-forked or the superior
basal sometimes bearing a few simple or once-forked branches.

Sori small, apical or sometimes dorsal on the simple branches
of primary branches of pinnae's midveins, or on the inner or
both of basal veinlets of the compound, mostly becoming con-
fluent, an oval spot visible beneath each sorus: indusia orbicular,
subentire or partly crenulate or suberose.

Spores ovoid or bean-shaped, with conspicuous, irregular,
wing-like borders.

Habitat. Woodlands, especially open woods, wooded banks
and store walls: often among rocks.

Christmas Fern 87

Range. Nova Scotia and New Brunswick to Wisconsin,
Iowa, Mississippi, and Florida.

Polystichum acrostichoides (Michaux) Schott, Gen. Fil. 1834.
Nephrodium acrostichoides Michaux, Fl. Bor. Am. 2 : 267. 1803.
Aspidium acrostichoides Swartz, Syn. Fil. 44. 1806.
Dryopteris acrostichoides Kuntze, Rev. Gen. PI. 2: 812. 1891.

THE simplest leaf-blade of Polystichum acrostichoides seen is
obcordate (PL XVIII, Fig. i). It contains a vein with two simple
branches, one of which occupies each of the lobes. The leaf-
blade becomes next more complexly lobed (Fig. 2 a 5), and its
midvein lengthens, and sends out additional primary branches.
The formation of pinnae is then carried out, and the venation
develops in the manner usual in ferns with pinnate venation.

The pinnae form gradually, appearing first as mere lobes.

At first the base of the leaf- blade is cuneate (Figs, i, 2 a b).
It is rendered truncate before the first pair of pinnae become
distinct (Fig. 4^), and then cordate (Fig. 3), by a broadening
of these two pinnae.

In the early leaves the pinnae are at first short and blunt,
sometimes, in the very early leaves, even wedge-shaped or cuneate
fan-shaped. They lengthen gradually, and become in highly
developed leaves acute or sometimes acuminate.

When newly formed, the pinnae in the very early leaves are
apt to be cuneate at base and are sometimes nearly or quite
equilateral, but a disposition to develop the upper side of the
pinna at the expense of the lower is shown at a very early stage
of the leaf-development. For some time this merely causes
the pinna to appear one-sided, but finally it results in the pro-
duction of the basal auricle seen in the mature leaves, which is
an incipient pinnule, and is occupied by the superior basal

88 Christmas Fern

primary branch of the pinna's midvein. This auricle some-
times, in very highly developed leaves, actually becomes a pin-
nule, as will be seen further on. The lower basal sides of the
pinnae mostly remain more or less oblique to the rachis.

The early leaves are crenately toothed or lobed, but one or
more spinulose or at least apiculate lobes are usually to be seen
before the first pair of pinnae becomes distinct. More spinulose
points appear in subsequent leaves, until the blunt teeth or lobes
are almost or quite superseded. Each spinulose point occurs
at the apex of a veinlet of the leaf, but one is not present at the
apex of every veinlet. In the later leaves there is usually one or
more to every primary branch of the pinnae's midveins.

The leaf becomes fertile first above and the fertile pinnae
are contracted.

In some plants, some or all of the leaves become very highly
developed, with the following results. In the fertile leaves the
soriferous zone extends downward, forming a sort of triangle,
the pinnae, like the leaf-blade itself, becoming soriferous first
at the apex, and their soriferous parts mostly becoming con-
tracted. Incisions occur between the primary branches of the
pinnae's midveins and sometimes deepen sufficiently to render
the leaf subbi pinnate. These primary branches, constituting
the midveins of the pinnae's segments, are more complex than
in the usual pinnae.

The so-called "vars." " schweinitzii " Beck, and "incisum "
Gray, are based on these highly developed leaves. These leaves
are usually very large and densely soriferous, and, as Mr. A. A.
Eaton has pointed out, appear to be the product of extreme
luxuriance of the plant. From the following facts and from my

* See Fern Bulletin, 8: 13. 1899.

Christmas Fern 89

own observations, it appears that they are likely to be induced by
anything acting as a strong stimulus to the plant, such as sunlight,
or an unusual supply of food brought within the plant's reach by
heavy rains. Mr. Eaton reports finding them late in the season
in the second growth of vigorous plants, although fruiting lightly
in such cases. They are often to be seen in plants exposed to
the sun from the cutting down of surrounding woods. Mr.
Eaton states that they are seldom found in plants growing in
shade, and that they disappear in localities when surrounding
trees that have been cut down are replaced by others. In short,
we have here, apparently, the remarkable case of a plant often
stimulated to a height of leaf-development far beyond the usual
one, and lapsing to its usual state when the stimulus is with-
drawn.

EXPLANATION OF THE PLATES.

PLATES XVTII-XX. — CHRISTMAS FERN. Polystichum acrostichoides.
Plate XVIII. — 1-6. Young leaves and plants in early stages of development.
2. Young plant attached to prothallus. Plate XXIX. — i, 2. Young leaves in
later stages of development. Plate XX. — i. Mature fertile leaf. 2. Fertile
pinna of same, X 2^. 3. Sterile pinna of same, X 2^. 4, 5. Sections of
sterile pinnae of more highly developed mature leaves, X 2^.

PLATE XVIII. — CHRISTMAS FERN

PLATE XIX. — CHRISTMAS FERN

PLATE XX.— C

'MAS FERN

CHAPTER XI
SLENDER CLIFF-BRAKE

Cryptogramma Stelleri.

Rootstock creeping, ivory-white or yellowish, slender, cord-
like, sparingly furnished with minute, pale, appressed, ovate,
acuminate, delicately reticulate scales with elongate cilia at
margin : leaves scattered : roots few, capillaceous, springing from
all sides of rootstock.

Leaves ascending, dimorphous, four to eight and four-fifths
inches long, the sterile usually the shorter; tender, withering
early, often before September.

Petioles slender, two to five inches long, usually longer than
blades, straw-colored to brown, palest above, slightly polished,
grooved on face and sides, the grooves less distinct below, bearing
a few scales: scales broadly to narrowly lanceolate, otherwise
similar to scales of rootstock: fibrovascular bundle solitary,
more or less rolled up or folded at ends or sometimes barely
curved.*

Blades ovate or ovate-oblong or ovate-deltoid, pinnate below,
toward apex pinnatifid: pinnae few, alternate or opposite, once
or twice pinnatifid, in largest sporophylls sometimes pinnate
below, becoming simple toward apex of blade, the lower often

* C. E. Waters.

94 Slender Cliff-Brake

short-stalked, the upper sessile and decurrent: sporophylls com-
monly more deeply cut than sterile leaves: ultimate segments
adnate-decurrent, the inferior mostly longer than the superior;
fertile segments lanceolate or linear-oblong on the smaller oval
or roundish, obtuse or appearing acute or subacute from the re-
flexed margins; the apical mostly the longest; sterile segments
obovate or ovate or roundish, crenately toothed or lobed, obtuse :
rachis greenish or below brown, grooved on face: surfaces gla-
brous: color pale green: texture thin, membranous.

Venation conspicuous, pinnate, free: primary branches of
midveins of fertile segments simple to twice-forked or rarely bear-
ing several simple or once-forked branches, commonly simple or
once-forked: primary branches of midveins of sterile segments
varying as in fertile segments, the average more complex than
average of latter: midveins sometimes not evident in small seg-
ments.

Sori clustered on upper part of veins: indusia consisting of
reflexed altered margin of segments, extending along sides and
often around apices of segments or in segments bearing few scat-
tered sori sometimes present only at soriferous points, at length
opening out more or less flat, delicately membranaceous, the
margin more or less erose or minutely denticulate or entire.

Spores spheroid-tetrahedral, obscurely trivittate.

Habitat. Clefts and ledges of shaded moist calcareous rock,
or on sandstone, mica-schist, or gneissoid rock;* particularly
near streams and lakes in cold mountain glens and ravines.

Range. Labrador to Alaska, south to Massachusetts, Penn-
sylvania, Illinois, Iowa, and in the Rocky Mountains to Colo-
rado.

* See Fern Bull. 10 :$6. 1902. Also Torreya, 2: 176. 1902.

Slender Cliff-Brake 95

Crypto gramma Stelleri (S. G. Gmel). Prant, Engler's Bot. Jahrb. 3: 413.
1882.

Pteris Stelleri. S. G. Gmel., Nov. Comm. Acad. Sci. Petrop. 12: 519.
PL XII, /. i. 1768.

Pellaa Stelleri. Watt, Can. Nat. : 3 158. 1867.

Pteris gracilis. Michaux, Fl. Bor. Am. 2: 262. 1803.

Pellaa gracilis. Hooker, Sp. Fil. 2: 138. PL CXXXIII. B. 1858.

I HAVE not been able to obtain leaves of Crypto gramma Stelleri
portraying earlier stages of leaf-development than the leaves
figured in PI. XXI, but from the figures the general develop-
ment of the form and venation of the leaf can be seen.

It will be noted that the venation is pinnate, and that when
new segments form on the leaf, many duplicate to a certain
extent the earlier segments. For instance, compare Figs, i a,
2 a, 4 a, 6 a, 8 a (PL XXI), and 2 a (PL XXII).

It will also be noted that the fertile leaf figured has no ter-
tiary segments (PL XXII, Fig. i). Tertiary segments are often
lacking in the mature leaves.

The incision by means of which the first basal primary
branch of the mid vein of any one of the leaf's segments is set
apart to constitute the midvein of a new segment sometimes
occurs while the midvein of the existing segment is little de-
veloped, and before other incisions occur in this segment: which
often gives the subdividing segment the appearance of being cut
vertically into two nearly equal parts.

The midveins in newly formed segments are sometimes not
developed beyond two simple primary branches. In segments
in later stages of development they are conspicuously developed.

In the transformation of the sterile leaf into a sporophyll,
the leaf's petiole lengthens, and the leaf-.blade's margin recedes
slightly and folds backward on the sides of the leaf's segments

96

Slender Cliff-Brake

and winged midribs. The sporophyll thus is longer than the
sterile leaf, and has slightly less complex veins and narrower
and more distinct segments.

EXPLANATION OF THE PLATES.

PLATES XXI, XXII. — SLENDER CLIFF-BRAKE. Cryptogramma Stelleri.
Plate XXL— 1-8. Leaves in different stages of development. Plate XXII.—
i. Mature fertile leaf . 2. Mature sterile leaf . 3. Section of fertile leaf, X i\.

a

^- &

•

a

PLATE XXI. — SLENDER CLIFF-BRAKE

PLATE XXII.— S

CHAPTER XII

SILVERY SPLEENWORT

Athyrium thelypteroides.

Rootstock creeping, forking, brown, green at tips, bearing
delicate, pale-brown, lanceolate or ovate-lanceolate or ovate-
deltoid, acuminate, slightly toothed or ciliate scales: roots
brown, coarse, copiously branching, springing from rootstock
and junctures of petiole and rootstock.

Leaves twenty to forty-seven inches long, five to twelve inches
broad, sensitive to frost.

Petioles eight to twelve inches long, shorter than blades; at
base dark-brown or at first partly green, turgid-compressed,
angled laterally and toothed along angles; above greenish-
straw-colored or straw-colored or brownish when dried, furrowed
on face; somewhat scaly and pubescent: scales pale-brown,
broadly ovate to lanceolate to linear, acuminate, entire, the
linear often, at least the upper, articulated at apex: hairs articu-
lated, marked at joints and sometimes lengthwise in brown or
golden-brown: fibrovascular bundles two, strap-shaped, uniting
below blade into one somewhat U-shaped in section.

Blades lanceolate or ovate-lanceolate, gradually or abruptly
narrowed toward apex, somewhat narrowed at base, pinnate,
pinnatifid toward apex: apex acuminate, undulate to serrulate

ioo Silvery Spleenwort

or serrate: pinnae sessile or very short-stalked, linear-lanceolate,
acuminate, or the uppermost acute to obtuse, passing toward
apex of blade into obtuse segments, deeply pinnatifid, the apices
undulate to serrulate or serrate: pinnae's segments oblong or
ovate-oblong, obtuse or subacute, serrate or crenate, often ob-
scurely so, or incisely serrate or lobed: rachis furrowed on face,
at least above, toward base bearing a few scales which are
articulated at apex arid similar to those of upper part of
petiole: surfaces studded, especially along rachis, midribs and
veins, with articulated hairs marked at joints and sometimes
tinged otherwise with golden-brown: color green: texture her-
baceous.

Venation pinnate, free or with occasional areolae: primary
branches of midveins of pinnae's segments commonly simple,
sometimes once-forked, especially in the more deeply cut seg-
ments, or in latter bearing a few simple branches.

Sori borne each on a primary branch, when this is simple,
of a midvein, when it is compound, extending along or wholly
upon its superior basal branch, opening toward midvein; single
and oblong or linear or the smaller suboval, or on veins that are
both primary branches of one midvein and superior basal branches
of primary branches of another, often opposed in pairs (dipla-
zioid) for the whole or part of their length, one sorus of each
pair opening toward one midvein, the other toward the other
midvein, the two often connate at outer end forming an athyrioid
sorus which is either hamate or hippocrepiform ; indusia silvery
and arched when young, often pointed at ends, entire or sub-
entire.

Spores bean-shaped, irregularly and narrowly winged.

Habitat. Rich, damp woods and ravines, near banks of

Silvery Spleen wort 101

mountain streams, etc.; particularly in or on the outskirts of
cold woodlands.

Range. Nova Scotia and New Brunswick to Minnesota, Illi-
nois, Alabama, and Georgia.

Athyrium thelypteroides. Desvaux, Me*m. Linn. Soc. Paris. 6: 266. 1827.
Asplenium thelypteroides. Michaux, Fl. Bor. Am. 2: 265. 1803.
Athyrium acrostichoides. (Sw.)Diels, Die Nat. Pflanzeuf. i*:22^. 1899.

Asplenium acrostichoides. Swartz, Shrad, Journ. Bot., 1800": 54. 1801.

YOUNG leaves of Athyrium thelypteroides can be easily rec-
ognized in the field by their peculiar specific texture and the short
hairs studding their upper surface.

The venation is pinnate.

The early forms of the leaf are shown in Pis. XXIII, XXIV.

The early pinnae are very short and blunt. In the course
of development they, as well as the leaf-blade itself, lengthen
more and more and become at last drawn out at apex into a long
point.

In the mean time their segments, which at first are mere teeth
or lobes or barely defined, and contain each a simple, once-forked
or slightly more complex branch of the pinnae's midveins, become
well marked, oblong, slightly often obscurely toothed segments,
in which the branches of the pinnae's midveins have become well-
defined midveins with simple branches which occupy the seg-
ments' teeth. At this stage of development the leaf appears as
in PL XXV, Fig. i. In PL XXV, Fig. 3, is shown an enlarged
section of a pinna of a leaf at this stage.

Finally, in the most highly developed leaves, the pinnae's seg-
ments lengthen and become slightly pointed, the segments' teeth
enlarge and the incisions between them deepen, so that they
become lobes rather than teeth, and the vein occupying each lobe

102 Silvery Spleen wort

often becomes an incipient or more developed midvein with
simple branches (PL XXV, Fig. 2).

It will be seen that in one sense the last step is niere repetition
of what has gone before, and that it accords with this fern's
disposition to lengthen and point its leaf-segments as they de-
velop, to enlarge teeth into segments, and to develop branches
of midveins into midveins with branches. The leaves with
the highly developed pinnae are sometimes sterile, sometimes
fertile. While less common than the leaves that do not repre-
sent the height of the leaf -development, they are to be looked for
in any luxuriant mature plant, and are likely to occur on the
same plant with less well-developed leaves as it advances in
development: leaves also are likely to occur in which some of
the pinnae's segments are highly developed and others not.
There is apparently nothing here to denote subspecific variation,
or even monstrous development, or to entitle either the markedly
highly developed leaves or markedly less well developed but
mature leaves to a distinctive name. Yet the highly developed
leaves have received at least two such names, and in one instance
the less well developed have been interpreted as a variety of the
highly developed.*

In this fern each sorus is borne on a vein which stands, or on

* "Var. serratum" Lawson is apparently based upon the highly developed leaves.
SeeCanad. Nat. 181. 1864. "Athyrium acrostichoides thelypteroides" Gilbert is based
upon the less well developed leaves. See Fern Bulletin, 8:9-10, 1900. In his "List of
North American Pteridophyta," 15. 1901, Mr. Gilbert apparently reverses this arrange-
ment, calling the highly developed leaves the variety or " form," to which he gives the
name "A. thelypteroides f. acrostichoides."

Swartz appears to have drawn his original definition of his A . acrostichoides from the
highly developed leaves, judging from p. 82 of his Synopsis Filicum, where this definition
is quoted and appears side by side with a short definition of Michaux's A . thelypteroides,
which Swartz evidently considered distinct. The two definitions point respectively to the
highly developed and the less well developed leaves of this fern.

Silvery Spleen wort 103

two veins each of which stands, in the relation of a primary
branch or of a superior basal primary branch of a primary
branch to a mid vein, the sorus opening toward the mid vein.
On such veins as stand in one of these relations to each of
two mid veins two sori are often borne, one opening toward one
midvein, the other toward the other midvein. These sori are
either distinct (diplazioid) or connate at the outer end (athyri-
oid). For instance:

The mid veins of the pinnae's segments are also primary
branches of the pinnae's mid veins, hence diplazioid and athyri-
oid sori, or at least the opposed parts of such sori, often occur
on their superior basal primary branches. Such sori are found
particularly in the small uppermost pinnae and the apices of
the larger pinnae, where the pinnae's midveins are more dis-
tinctly mid veins (are less merged in midribs), than elsewhere.
In the pinnae in which the primary branches of the midveins of
the pinnae's segments are simple, the only midveins are the mid-
veins of the pinnae's segments and the midveins of the pinnae, hence
such sori occur only as above described — i.e., next the pinnae's
midveins or midribs, on the superior basal primary branches of
the midveins of the pinnae's segments, which in these pinnae
are the only veins standing in the required relation to each of
two midveins (PI. XXV, Fig. 3). In the pinnae in which the
midveins of the pinnae's segments bear branches, and so represent
incipient or well-defined midveins of the segments' lobes, such
sori occur on their superior basal branches (PI. XXV, Fig. 2).

In all the specimens of this fern that I have examined, I have
not been able to find the opposed parts of any diplazioid or athy-
rioid sori on any vein that did not stand in such relations to two
midveins as to lead one to expect two sori upon it, or either of

104 Silvery Spleenwort

the unopposed parts, if any, on any vein that did not stand in
such a relation to one of the midveins as to lead one to expect
a single sorus on it: judging from the positions of the single
sori on the other veins of the specimens. The material exam-
ined comprise the collections of this fern in the New York Botan-
ical Garden, two specimens typical of the highly developed and
of the less well developed leaves kindly sent me by Mr. Gilbert,
and a large number of specimens collected in Vermont.

Union in formation of otherwise normal asplenioid sori is
thus, apparently, the explanation of the occurrence of athyrioid
sori in this fern. It is evident that athyrioid sori are liable to
occur in any Asplenium when, for any reason, two single sori
are borne in juxtaposition on opposite sides of the same vein.
That the union does not always occur when opportunity offers
is seen by the presence of the diplazioid sori in A. thelypter aides-

Either of the two sori that make up the diplazioid or the
athyrioid sori in this fern may or may not extend down the
vein as far as the midvein toward which it opens. If, in the
athyrioid sorus, the two extend an equal distance, we have a
hipprocrepiform sorus, if an unequal, a hamate sorus, or one of
the two may be so short as to be barely distinguishable. Since
in the athyrioid sorus both are united at the outer end, one can-
not extend at that end farther on the vein than the other, but
one can and often does in the diplazioid.

By some botanists A. thelypteroides, A. filix-fcemina, and A.
cyclosorum, the three representatives of Athyrium in the United
States, are included in the genus Asplenium. All three ferns
have a greater or less number of athyrioid sori on their leaves,
but it appears from all the specimens that I have seen that the
occurrence of the athyrioid sori is due to the same cause in all.

Silvery Spleenwort 105

A. thelypteroides, A. filix-josmina, and A. cyclosorum are
undoubtedly congeneric. In habit and general character they
are more nearly related to the group of Dryopteris of which D.
noveboracensis, D. thelypteris, and D. simulata are represent-
atives than to some species of Asplenium. A. thelypteroides is so-
named from its resemblance to D. thelypteris, and D. simulata
from its simulation of a form of A. filix-fcemina. Shorten
athyrioid sori sufficiently and we have dryopterioid sori: some
of the short athyrioid sori often seen, on leaves of A. cyclosorum
and A. filix-joemina particularly, are not distinguishable from
sori of Dryopteris.

The evolution of Dryopteris from an ancestor with asplenioicf
sori, and also the manner in which the change in the sori may
have come about, is thus suggested. For instance, let us suppose
that athyrioid sori were produced first in some Asplenium by
casual union of otherwise normal asplenioid sori, as they are
apparently produced in A. thelypteroides, A. filix-fcemina, and A.
cyclosorum; a tendency to produce such sori might be inherited
by the descendants of that Asplenium and augmented until these
sori came to be produced not only on such veins as at first, but
on other veins as well, and finally to supplant the asplenioid
sori.

EXPLANATION OF THE PLATES.

PLATES XXIII-XXV. — SILVERY SPLEENWORT. Athyrium thelypteroides.
Plate XXIII. — i. Young plant attached to prothallus. 2-6. Young leaves
in early stages of development. Plate XXIV. — Young leaves in later stages of
development. Plate XXV. — i. Mature sterile leaf. 2. Section of fertile
pinna of highly developed mature leaf, X 2\. 3 . Section of fertile pinna of
less highly developed mature leaf, X z\.

PLATE XXIII. — SILVERY SPLEENWORT

PLATE XXIV.

RY SPLEENWORT

PLATE XXV.-

- ' 3 ^ T ^ ***^-&^ (Sr.&* • & *^^r <£*^.

•^mM%%%

SHY SPLEENWORT

CHAPTER XIII

NEW YORK FERN

Dryopteris noveboracensis.

Rootstock wide-creeping, forking, brown, slender, bearing a
few minute, pale-brown, ovate-deltoid, acuminate scales; leaves
scattered along extensions of rootstock, forming caespitose crowns
at its growing ends: roots few, springing from rootstock.

Leaves ascending or suberect, withering in autumn, six to
twenty-nine inches long, sporophylls usually longer and narrower
than sterile leaves.

Petioles about one-fifth to one-third as long as leaves, slender,
brownish-straw-colored, furrowed on face, bearing a few small,
pale-brown, ovate, acuminate scales: fibrovascular bundles two,
flattish.

Blades lanceolate, tapering both ways, two and one-half to
seven and one-half inches broad, pinnate: apex pinnatifid,
long-acuminate: pinnae about nineteen to thirty pairs, sessile,
alternate or opposite; principal pinnae deeply pinnatifid, acu-
minate : upper and lower pinnae acute to obtuse, the lower more
or less distant and gradually reduced to mostly toothed or simply
auriculate lobes: segments oblong or oblique, obtuse to acute,
entire or crenately toothed : margins ciliate : rachis and midribs
pubescent: surfaces otherwise sparingly pubescent along veins:

1 1 o New York Fern

pubescence and cilia consisting of minute straight whitish hairs:
texture thin, herbaceous: color light subdued green.

Venation pinnate, free: primary branches of midveins of
pinnae's segments simple or a few, especially in toothed segments,
once-forked or bearing several branches.

Sori minute, mostly submarginal, variously placed on vein-
lets: indusia delicate, whitish, bearing on margin, and sometimes
sparingly on surface, minute yellowish globules or glands, often
also a few short, straight, whitish hairs.

Spores ovoid-reniform, muricate, with more or less of a semi-
transparent border or wing along the slightly hollowed side.

Habitat. Woodlands and copses.

Range. Newfoundland to Ontario and Minnesota, south to
northern Georgia, Alabama, and Arkansas.

Dryopteris noveboracensis (L.). A. Gray, Manual, ed. i. 630. 1848.
Polypodium noveboracense. L. Sp. PI. 1091. 1753.
Nephrodium noveboracense. Desv. Ann. Soc. Linn. 6: 257. 1827.
Aspidium noveboracense Swartz, Schrad. Jour. Bot. 1800'. 38. 1801.

THE development of the form of the leaf of Dryopteris
noveboracensis can be readily seen from Pis. XXVI, XXVII.
It will be noticed that the tapering of the base of the leaf- blade,
which is so marked a characteristic of the mature leaf, is lack-
ing at first, and is produced later by a combination of extreme
although gradual development of the principal pinnae and very
slight development of the lower. In the leaf-development of the
nearly related Dryopteris simulata, the development of the prin-
cipal pinnae and the lower pinnae is more uniform and a differ-
ent shape is thus given to the leaf.

EXPLANATION OF THE PLATES.

PLATES XXVI, XXVII. — NEW YORK FERN. Dryopteris noveboracensis.
Plate XXVI. — 1-7. Young leaves in different stages of development. Plate
XXVII. — i. Mature sterile leaf . 2. Section of fertile pinna, X 2$.

PLATE XXVI.

YORK FERN

PLATE XXVII.

w YORK FERN

CHAPTER XIV

MASSACHUSETTS FERN

Dryopteris simulata.

Rootstock wide-creeping, forking, cordlike, brown, sparingly
furnished with small, pale-brown, ovate-deltoid, reticulate scales :
leaves clustered or approximate, springing from all sides of root-
stock: roots few and coarse, clothed with mustard-colored wool,
springing from rootstock.

Leaves erect or ascending, withering in autumn, twelve to
forty-eight inches long or longer, sterile leaves the shorter, some-
times only half as long as sporophylls.

Petioles six to twenty inches long, slender, stramineous, fur-
rowed on face, bearing a few pale-brown, ovate-acuminate scales;
at base dark brown, slightly compressed: fibrovascular bundles
two, flattish.

Blades six and four-fifths to twenty-two inches long, two to
seven and one-half inches broad, oblong-lanceolate, occasionally
oblong-deltoid, pinnate, gradually or abruptly narrowed toward
apex: apex pinnatifid, long-acuminate: pinnae twelve to twenty-
one pairs, alternate or opposite, sessile, parting readily from
rachis, . elliptic-lanceolate, acuminate, deeply pinnatifid, the
lower sometimes pinnate at base, basal pair usually introse: seg-
ments oblong or oblique, obtuse, entire or sometimes toothed:

1 1 4 Massachusetts Fern

margins ciliately pubescent, in sporophylls slightly revolute:
surfaces finely pubescent, lower surface studded with minute
yellowish glands: rachis stramineous, narrowly furrowed on face,
texture herbaceous: color light or deeper green, rather bright.

Venation pinnate, free : primary branches of mid veins of pin-
nae's segments simple, or a few forked.

Sori rather large, submarginal or medial : indusia finely glan-
dular on margin.

Spores red-brown, under a lens yellow, roughened with ir-
regular ridges.

Habitat. Woodland swamps; sphagnous thickets, roadsides
and pastures ; wet banks of streams, etc. ; most luxuriant in
shaded swamps. In plants exposed to the sun the pinnae are
usually conduplicate and the leaf-blade somewhat contracted,
suggesting a narrow form of Athyrium filix-jcemina. Often ac-
companied by Lorinseria areolata.

Range. Maine to Maryland. Also Vermont and New York,
and reported from Indian Territory and Missouri. Probably of
wider range.

Dryopterissimulata. Davenport, Botanical Gazette, 19: 497. 1894, as syn.
Nephrodiums imulatum. Davenport, Botanical Gazette, 19: 497. 1894,
as syn. Also Rhodora, 4: 10. 1902.

THE development of the form of the leaf-blade of Dryopteris
simulata needs little explanation beyond that given by the figures. *
From these may be seen the manner in which the lateral pri-
mary segments of the early leaves become the pinnae with small
lobes of later, and these lobes lengthen into the segments, some-
times in turn becoming lobed, of the pinnae of the mature leaves, f

* Plates XXVIII, XXIX, XXX.

t For comparison of the leaf-development in this fern and in D. noveboracensis see
page 94.

Massachusetts Fern 115

The delicate pubescence of the leaf-blade and the dark color
at the petiole's base are to be seen in the leaf at most if not all
stages of development.

The yellowish glands have been found on the leaf-blades of
all the leaves examined, excepting one or two extremely young
ones, and offer the simplest means of distinguishing this fern
from D. noveboracensis and D. thelypteris at any stage of leaf-
development at which they are likely to be confused.

It is often said that the venation offers an easy means of
distinguishing D. simulata from D. thelypteris, and this is true
of the venation in the mature leaves. In these, the primary
branches of the mid veins of the pinnae's segments are mostly
once forked in D. thelypteris and simple in D. simulata, except
in large, often toothed segments, which are examples of leaf-
development carried slightly further than usual and in which,
consequently, they are more complex. But in the early leaves
of both plants the degree of complexity of any of the venation of
the pinnae's segments is changeable, depending upon the segment's
state of development, and is not to be relied upon as a distin-
guishing characteristic until a fairly advanced stage of leaf-
development is reached. As the venation in both is pinnate,
the entire venation of the segments is formed by the lengthening
and branching of the branches of the midveins in the early pin-
nae, which takes place during the leaf-development.

EXPLANATION OF THE PLATES.

PLATES XXVIII-XXX. — MASSACHUSETTS FERN. Dryopteris simulata.
Plate XXVIII. — i, 3-7. Young leaves in different stages of development. 2.
Very young plant. Plate XXIX. — 8. Young leaf in later stage of development.
Plate XXX. — i. Mature sterile leaf. 2. Section of fertile pinna of mature
leaf, X 2$.

PLATE XXVIII. — MASSACHUSETTS FERN

PLATE XXIX. — MASSACHUSETTS FERN

PLATE XXX.

CHUSETTS FERN

CHAPTER XV
MARGINAL SHIELD FERN

Dryopteris marginalis.

Rootstock caudiciform, stout, densely chaffy: scales large,
light golden-brown or brown or rust-colored, lance-linear, acu-
minate, entire or near apex slightly ciliate-toothed, sometimes
appearing articulated from a transverse contraction: leaves in a
crown: roots springing from rootstock or junctures of rootstock
and petioles, singly or by twos.

Leaves ascending, six to thirty-eight inches long, two to nine-
teen inches broad, prostrated in autumn, gradually withering more
or less during winter.

Petioles shorter than blades; at base dark or reddish-brown,
sometimes tinged with plum color, turgid; above more slender,
pale-green or reddish-brown, stramineous when dried, furrowed
on face, chaffy: scales thickly clothing base of petiole, those
above fewer, light golden-blown or shining rust-colored, large
and small mixed, lanceolate to linear, acuminate, subentire or
ciliate-toothed, sometimes contracted like those of rootstock:
fibrovascular bundles five to nine in base, five in apex, of petiole,
roundish-strap-shaped; the two anterior largest, furrowed on
sides or roundish- wedge-shaped in section.

Blades ovate-oblong or ovate-lanceolate, bipinnate or sub-

I2O Marginal Shield Fern

bipinnate : apices pinnatifid, becoming dentate or crenate or sub-
serrate or near tip undulate or entire, long-acuminate: pinnae
alternate or opposite, approximate or distant, short-stalked, the
uppermost subsessile to sessile, lanceolate or ovate-lanceolate, or
the basal unequally lanceolate-deltoid; mostly broadest above
the base or below the middle: pinnules mostly approximate, the
innermost largely subsessile to short-stalked, otherwise mostly
adnate to rachis and somewhat decurrent, oblong or oblong-
lanceolate, often oblique, sometimes slightly falcate, obtuse or
subacute or rarely acute, entire to dentate or crenately toothed or
lobed, or pinnatifid on the inner side or both sides: margins mi-
nutely paleaceous at or near nodes of pinnae's lobes to glabrous:
surfaces somewhat chaffy along or near rachises : scales minute or
larger, lance-linear or linear, acuminate, ciliate-toothed : rachises
furrowed on face : color dark-bluish-green or sometimes yellow-
ish: texture subcoriaceous.

Venation pinnate, free: veinlets mostly curved: lobes of
pinnules each occupied by a primary branch of the pinnule's
midvein: primary branches of pinnules' midveins mostly once-
forked or bearing branches which are simple or once-forked or
in the larger lobes bear simple branches, or in smaller pinnules
and apices of pinnules simple.

Sori submarginal, borne on the simple superior basal branches
of primary branches of pinnules' midveins or on superior basal
branches of the compound, below or more rarely on apices of
veinlets: indusia at first white, becoming lead -colored, finally
brown, orbicular-reniform, convex at first, entire, glabrous.

Spores ovoid-reniform, with a narrow crenulate wing.

Habitat. Woods, roadsides, and stone walls: particularly on
or near rocks, or on old logs or stumps in wet woods and swamps.

Marginal Shield Fern 1 2 1

Range. Nova Scotia to British Columbia, south to Indian
Territory, Arkansas, Alabama, and Georgia.

Dryopteris marginalis (Linnaeus). A. Gray, Manual, ed. i, 632. 1848.
Poly podium marginale. Linnaeus, Sp. PL 1091. 1753.
Nephrodium marginale. Michaux, Fl. Bor. Am. 2 : 267. 1803.
Aspidium marginale. Swartz, Syn. Fil. 50. 1806.

THE venation of the leaf of Dryopteris marginalis is pinnate.

The development of the leaf's form can be seen from Pis.
XXI, XXXII.

It will be seen that the development of the leaf's segments is,
on the whole, gradual. Excepting the development of the basal
primary segments (pinnae), whose segments begin to develop
almost coincidently with the pinnae themselves, the segments
mostly become fairly well formed before their subdivision into
segments is more than obscurely indicated, although it is early
suggested by minute notches occurring between their midveins'
primary branches. The segments of each successive series
following the primary series start with much the same form and
venation, and undergo, so far as their development extends,
substantially the same changes in form and venation as those
of the preceding series: since they are a part of those, they
obviously cannot reach the same height of development. In
addition, the formation of each series following the primary
one begins on the segments first formed (lowest on the leaf's
stalks) of the preceding series, and involves successively the
segments successively next formed (next lowest). As a result:

In the older leaves, segments in all stages of development
can be seen. For instance, tertiary segments are often to be
seen at the base of the leaf while some of the primary segments
(pinnae) near its apex are still in the subentire state. Also,

122 Marginal Shield Fern

segments at similar stages of development but belonging to
different series are more or less alike. For example, compare
the primary segment, Fig. 7 a (PL XXXI), with the secondary
segment, Fig. 8 a ; and the secondary segment, Fig. 6 b (PL XXXI),
with the tertiary segment, Fig. 2 b (PL XXXII).

As stated in the synoptical description of this fern, leaves
sometimes occur with the tertiary segments more highly developed
than in those figured. The scope of the leaf's development
and the fact that sori appear, at least sometimes, on the leaf at
an early stage of its development, have occasionally misled fern
students into giving different, distinctive names to the plants
at different stages of the leaf-development.

It will be seen from the figures that the long acuminate
apices of the leaf -blade, which are so conspicuous a feature of
the mature leaves that they have almost come to be looked upon
as an integral part of the plant's makeup, are lacking in the early
stages, and are gradually formed later in accordance with a
tendency of the leaf-blade itself and the segments of its succes-
sive series to lengthen and become more and more pointed at
apex as they become more and more complex. This tendency,
so marked in this fern, is common in many others, and especially
in those with pinnate venation.

EXPLANATION OF THE PLATES.

PLATES XXXI, XXXII. — MARGINAL SHIELD FERN. Dryopteris margin-
alls. Plate XXXI.— i. Young plant attached to prothallus. 2-8. Young
leaves in different stages of development. Plate XXXII. — i. Mature sterile
leaf. 2. Fertile pinnule of mature leaf, X 2$.

PLATE XXXI. — MARGINAL SHIELD FERN

PLATE XXXII—

CHAPTER XVI
SPINULOSE FERN

Dryopteris spinulosa intermedia.

Rootstock creeping, stout, chaffy: leaves clustered slightly
back of or partly encircling terminal leaf-buds: roots springing
from rootstock, often two or three to a petiole.

Leaves ascending or suberect, five inches to three feet long,
three inches to one foot broad, imperfectly evergreen.

Petioles two inches to one foot long, commonly shorter than
blades, chaffy: at base dark fuscous, turgid; above more slen-
der, green or at back slightly brownish or when dried greenish-
straw-colored, deeply channelled on face, slightly furrowed on
sides: scales tawny with darker centres or darker at points of
attachment only, ovate, acuminate, entire, when removed leaving
minute rigid points; the lower numerous, rather large; the
upper fewer, smaller: fibrovascular bundles five to seven in base,
three near apex, of petiole, the two anterior largest; somewhat
roundish-strap-shaped, on broader sides sometimes slightly hol-
lowed or furrowed.

Blades oblong-ovate, bi-tri -pinnate: apices pinnatifid, acumi-
nate: pinnae spreading, diverging from rachis at angle of about
sixty to ninety degrees, crowded or approximate or more distant,
alternate or opposite, the lower short-stalked, the upper subsessile

i 26 Spinulose Fern

to sessile, oblong-lanceolate, basal pair unequally deltoid-ovate:
pinnules diverging from secondary rachis at angle of about sixty
to usually a trifle less than ninety degrees, crowded or more
distant, alternate or opposite, mostly short-stalked or subsessile,
ovate-oblong, obtuse to acute, commonly subacute, pinnatifid or
pinnately divided, usually minutely, obscurely, and very spar-
ingly chaffy on under surface along midveins ; the inferior mostly
longest, in basal pinnae moderately elongate with the basal one
commonly shorter than the next: segments adnate-decurrent,
oblong or at least the larger ovate, on sides and apex serrately
toothed or lobed; teeth and lobes spinulose entire or spinulose-
toothed: rachises channelled on face, furnished, especially at
nodes of pinnae, sparingly with small or minute, linear or ovate,
acuminate, entire scales, secondary rachises very narrowly
winged: color commonly dark green: lower surface slightly
paler than upper, minutely glandular: glands unicellular, capi-
tate or cylindrical : texture firmly membranaceous.

Venation pinnate, free, marked on face of blade by depressed
lines : each tooth of blade occupied by a veinlet : primary branches
of midveins of pinnules' segments each, excepting sometimes the
superior basal one, occupying a primary lobe or tooth of the seg-
ment, in the entire one simple, in the toothed bearing simple
branches ^qual in number to the teeth : veinlets clubbed at apex.

Sori usually small, borne on primary branches, when these
are simple, of midveins of pinnules' segments ; when these branches
are compound, borne on their superior basal branches, dorsal or
subapical, the fertile veinlet mostly projecting beyond radius of
sorus: indusia whitish, delicately membranous, round-reniform,
bearing stalked and sessile glands, denticulate at margin.

Spores muriculate.

Spinulose Fern 127

Habitat. Woods, dry or damp, swamps, stone-walls, and
shaded hillsides. Often on crumbling logs or beneath ever-
greens.

Range. Labrador to Alaska, south to North Carolina and
Tennessee.

Dryopteris spinulosa intermedia (Muhlenberg) . Underwqod, "Our Na-
tive Ferns," ed. 4. 116. 1893.

A spi diu m intermedium Muhlenberg. Willdenow, Sp. PL, 5: 262. 1810.

Dryopteris intermedia. A. Gray, Manual, ed. i. 630. 1848.

Aspidium spinulosum var. intermedium. D. C. Eaton in A. Gray, Man-
ual, ed. 5. 665. 1867.

Nephrodium spinulosum var. intermedium. Davenport, Rhodora, 4: 53.
1902.

YOUNG plants of Dryopteris spinulosa intermedia are often to
be seen on old logs and stumps in wet woodlands.

The leaf is often deltoid at an early stage of develop-
ment, but usually changes in shape later; in what way can be
seen from Pis. XXXIII-XXXV.

The venation is pinnate. With rare exceptions each tooth
or simple lobe of the leaf- blade contains a veinlet. For instance :
in a leaf-blade consisting of two simple lobes, such as PL XXXIII,
Fig. i, represents, the primary midvein of the blade does not ex-
tend beyond two simple basal primary branches, each of which
occupies one of the lobes: in a blade consisting of three simple
lobes, a simple veinlet from its midvein occupies each of the lobes :
if a lobe is two-toothed, which is often the case in different stages
of the leaf's development, the vein belonging to that lobe has
two simple branches, each of which occupies one of the teeth.

It cannot be said, however, that with rare exceptions each
veinlet of the leaf-blade ends within a tooth or simple lobe. For
instance, in the mature leaves the incisions, by means of which

128 Spinulose Fern

the pinnules' segments are formed, are not always deep enough
to reach or pass the tips of the superior basal primary branches
of the segments. Consequently, these branches, whether simple
veinlets or not, may end within the unincised part of the pinnule
and not within teeth or lobes.

EXPLANATION OF THE PLATES.

PLATES XXXIII-XXXV. — SPINULOSE FERN. Dryopteris spinulosa inter-
media, Plate XXXIII. — 1-7. Young leaves and plants in early stages of
development. 1-3. Plants attached to prothalli. Plate XXXIV. — i, 2.
Young leaves in later stages of development. Plate XXXV. — i . Mature sterile
leaf. 2. Section of fertile pinna of mature leaf, X 2$.

PLATE XXXIII. — SPINULOSE FERN

•

PLATE XXXIV. — SPINULOSE FERN

/ *> ' ;

PLATE XXXV.-

FERN

CHAPTER XVII
WALKING LEAF

Camptosorus rhizophyllus.

Rootstock ascending, short, slender, somewhat chaffy: scales
minute, strongly reticulate in reddish-brown, lanceolate or nar-
rowly lanceolate-deltoid or, apparently abnormally, ovate, acu-
minate, entire or with a few short cilia: leaves fascicled at apex
of rootstock: roots springing from outer sides of junctures of
petioles and rootstock, one to each petiole.

Leaves two to fifteen inches long, decumbent or ascending,
imperfectly evergreen.

Petioles four-fifths of an inch to six inches long, slender, flaccid ;
below chestnut-brown about one-eighth to one-third of length;
above green ; laterally narrowly winged for more or less of length
from apex downward ; at base bearing a few scales similar to scales
of rootstock, sometimes an occasional narrow scale above: fibro-
vascular bundles two in lower part of petioles, roundish, uniting
above into one roundish-deltoid in section.

Blades lanceolate with flagelliform apex proliferous at tip,
or lanceolate or ligulate with obtuse or acute non-proliferous
apex; at base auricled, cordate, hastate, or, rarely, acute; auri-
cles sometimes prolonged laterally and obtuse to flagelliform,
occasionally proliferous at tip of prolongation : margins entire or

132 Walking Leaf

undulate or irregiuar or rarely incised: midribs prominent be-
neath: surfaces glabrous: color deep, lustrous green, or yellow-
ish-olive in age or in plants exposed to the sun: texture cori-
aceous or subcoriaceous.

Venation pinnate, anastomose: marginal veinlets largely free.

Sori linear, straight or curved, variously placed along veins,
some solitary, some confluent with ends of others, some conni-
vent, usually outwardly, or simply faced in pairs: indusia whitish,
delicately membranous, undulate at margin, attached at sides
or around outer ends of areolae or at leaf's margin to free veinlets,
those next midrib opening toward it, many of the outer opening
toward each other in pairs.

Spores ovoid, with winglike pellucid crenate margin.

Habitat. Limestone, gneiss, granite, quartzite, sandstone,
shale, and serpentine.* On cliffs, boulders, etc.,f usually on
shaded sloping rock coated with mossy earth. Over this the
leaves stretch, crossing one another: in the interstices the pro-
liferous tips of new leaves are inserted.

Range. Maine and southern Quebec to Minnesota, south to
Georgia, Alabama, and Kansas.

Camptosorus rhizophyllus (Linnaeus). Link, Hort. Berol. 2: 69. 1833.
Asplenium rhizophylla. Linnaeus, Sp. PI. 1078. 1753.

THE leaf first produced by the plant springing from the
proliferous tip of a mature leaf of Camptosorus rhizophyllus
often, if not always, represents a higher degree of leaf-develop-
ment than the first produced by the plant springing from the
prothallus. The blade of the latter leaf is either spatulate, ob-
cordate, or obreniform: if spatulate, a leaf with an obreniform

* See Fern Bulletin, 8:92, 1900. Also D. C. Eaton, N. Am. Ferns, i =56. 1878.
t In the limestone region of Vermont I have seen this plant lining the mouth of an
old well.

Walking Leaf 133

or obcordate blade usually follows it. The order of forms of the
blade in the scale of leaf -development is as follows: Spatulate,
obcordate or obreniform, cuneate and trilobed or broadly cuneate-
rhomboidal, roundish-ovate with truncate base, ovate, ovate-ob-
long, ligulate, and lanceolate. The blade's apex changes from
obtuse to flagellif orm ; and its base from truncate to cordate,
auriculate or hastate, and finally, although rarely, becomes de-
veloped laterally into long-drawn-out lobes, which are similar to
the flagelliform upper part of the leaf, and sometimes, like it, pro-
liferous at apex.

Although connate at base with the main part of the leaf-
blade, these lateral lobes are in reality partly formed pinnae.*
In them, as well as in the flagelliform upper part of the leaf-
blade, is shown the tendency of this fern's leaf to become
attenuate and proliferous at its apices, whether primary or
secondary.

The spatulate leaf-blade contains a simple or once-forked
vein. The obcordate and the obreniform each contain a once-
to twice-forked vein, and the trilobed and the rhomboidal each
a midvein with two simple or once-forked branches at apex and
two below. The development of the midvein continues in the
succeeding leaves. The midvein is contained finally in a midrib.

The veins are free at first, f The formation of areolae appar-
ently begins as the blade becomes truncate at base, when two
or more of the midvein's branches unite next the midvein. In
succeeding leaves the midvein's branches become more and
more anastomose until they form a network that extends nearly
to the leaf-blade's margin. They are united in such a way that
the veinless border of the blade seems to cut the network ; appar-

* See page 12 t See page 18.

1 34 Walking Leaf

ently only such marginal veinlets are free as would be if it
actually did so.

Each of the lateral lobes of the leaf, if at all pronounced,
contains more or less of a distinct mid vein, which starts from the
starting-point of the basal areole next the leaf's midrib. These
midveins are formed by the areolae through the centre of each
lobe gradually straightening in such a way as to form a double
row of areolae, the veinlets that form the side in common of the
two single rows making up the double one, thickening and con-
stituting a midvein.

EXPLANATION OF THE PLATE.

PLATE XXXVI. — WALKING LEAF. Camptosorus rhizophyllus. i-n.
Leaves and young plants in different stages of development, i, 2. Young
plants attached to prothalli. 9. Mature fertile proliferous leaf uncoiling at
tip. 10. Mature fertile proliferous leaf, with young plant springing from tip
and extended auricles at base. n. Mature fertile non-proliferous leaf. 12.
Section of fertile leaf, showing extended auricle, X 2^.

CHAPTER XVIII

NARROW-LEAVED CHAIN-FERN

Lorinseria areolata.

Rootstock wide-creeping, forking, dark brown, at least when
dried, furnished with light brown, concolorous, ovate, acute,
entire scales: leaves scattered, distant or approximate, borne on
all sides of rootstock; roots springing from rootstock, equalling
or slightly exceeding the petioles in number.

Leaves dimorphous, somewhat sensitive to frost; sporophylls
erect, twelve to twenty-eight inches long; sterile leaves shorter.

Petioles compressed at base, somewhat chaffy, bordered on
each side for some distance from apex downward by a fine ridge:
in sterile leaves longer to shorter than blades, slender, chestnut-
brown below, often furrowed on face and sides, at least when
dried, the lateral furrows containing the lateral ridges: in sporo-
phylls stouter, elongate, rigid, light chestnut-brown to purplish-
ebony, subterete: scales hyaline, ovate, acuminate, entire or
subciliate, thinly clothing base of petiole, upper scales few and
scattered or absent: fibrovascular bundle solitary, arched at
back, more or less channelled on face.

Blades of sterile leaves ovate-deltoid, below pinnate or sub-
pinnate, above parted, gradually or abruptly narrowing to the
often sinuate or sinuately lobed base of the ovate-lanceolate or

138 Narrow-Leaved Chain-Fern

lanceolate usually undulate apex: segments about eight to
thirteen pairs, connected by a costal-wing or below by a fine
ridge, oblong-lanceolate or lanceolate, largely undulate or some-
times sinuate, the basal narrowed at base, those above gradu-
ally widening, third or fourth pair usually longest: apices acute
or acuminate; margins serrulate, or entire in and near costal-
wing: rachis and midribs furnished along the sides beneath
and sometimes very sparingly above with small, ovate, acuminate,
entire or subciliate scales; midribs often brownish or olive, at
least when dried: surfaces otherwise glabrous, the upper deep
glossy green, the lower paler: texture softly membranaceous.

Blades of sporophylls ovate-oblong, below pinnate, above
deeply pinnatifid, abruptly narrowing to the often lobed base
of the elongate linear apex: divisions narrowly linear, alternate
or opposite, connected by a costal- wing or ridge: apices acute,
margins entire in costal-wing, otherwise undulate or denticulate,
usually slightly revolute: rachis colored like petiole or above
greenish: scales small, ovate, acuminate, subciliate, borne as in
sterile leaves: surfaces glabrous otherwise, the upper dark green,
the lower paler: texture firmly membranaceous.

Venation of sterile leaves pinnate, anastomose; marginal
veinlets mostly free, simple or once forked: paracostal areolae
elongate, parallel or subparallel to costa, those next the rachis
giving rise successively at ends to midribs of the segments, those
next the midribs to mid veins (when present), of the segments'
lobes; in very narrow parts of costal-wing contracted to vanish-
ing point or veinlets forming their outer edges alone visible, in
form of fibers coherent with costa: outer areolae shorter, oblique
or in costal-wing subparallel or parallel to costa, oblong, hex-
agonal or pentagonal : midveins rarely present in lobes of segments.

Narrow-Leaved Chain-Fern 139

Venation of sporophylls pinnate, anastomose: paracostal
areolae as in sterile leaves, mostly sending out to margin of blade
veinlets which either are short with free, almost exsected apices
or, especially neafr nodes of pinnae, prolonged and form a few
areolae.

Sori sausage-shaped, linear or the smaller oblong, each borne
on a veinlet forming the outer edge of a paracostal areole and
contained in a depression of the leaf: indusia subcoriaceous, at
first enwrapping sporongia, the free inner margin somewhat
crenulate.

Spores ovoid-spherical or obscurely spheroid-tetrahedral, ap-
parently smooth.

Habitat. Woodland swamps or damp thickets: usually in
shade. In plants exposed to the sun the texture of the leaves
becomes thickened and the venation somewhat obscure. Often
accompanying Dryopteris simulata.

Range. Maine to Florida, Louisiana, and Arkansas. Also in
Michigan.

Lorinseria areolata. Presl, Epim. Bot. 72. 1849.
Acrostichum areolatum. Linnaeus, Sp. PI. 1069. 1753.
Woodwardia areolata (L.). Moore, Index Fil. XLV. 1857.
Woodicardia angustifolia. J. E. Smith, Mem. Acad. Roy. Sci. Turin, 5:
411. 1793.

As elsewhere stated,* the plants of Lorinseria areolata, Onoclea
sensibilis and Osmundia spectabilis when very young are liable to
be mistaken for one another, but can be easily identified. L.
areolata and O. sensibilis are closely allied, but bear only the
most distant relationship to O. spectabilis.

In L. areolata the young leaf- blade is at first roundish-cune-

* See page 124.

140 Narrow- Leaved Chain-Fern

ate, next oblong or obovate with cuneate or truncate base, then
elliptical or oblong-ovate or oblong-lanceolate and early lobed
below. From PI. XXXVII can be seen how, in subsequent leaves,
the lobes enlarge, and more and more lobes are formed, from
the part of the blade above the first lobes; which enlarge also;
until the lobes become the primary segments and the part of the
blade left above them forms the apical section of the mature leaf.
These segments sometimes in turn become lobed. Their lobes
are rounded, and, so far as I have seen, are less deep than the
lobes of the primary segments in O. sensibilis.

The margin of the blade, except at base, is more or less
crenulate at first. Later the crenulation becomes serrulation.
The number of teeth mostly corresponds with the number of
marginal veinlets: except near the rachis, each marginal veinlet
usually terminates within a tooth.

The veins are free at first. The leaf's primary midvein, if
not evident at the beginning, becomes so before areolae appear.
One or two areolae form first in the upper part of the blade while
the blade is still simple. Others follow in subsequent leaves,
forming downward on each side of the primary midvein, and
thence outward until the margin of the blade has the appearance
of cutting the network of veins: the marginal veinlets are mostly
free. The primary midvein is finally more or less hidden in the
rachis of the mature leaf.

The mid veins of the leaf's primary segments (secondary
mid veins) are formed in the same way as in O. sensibilis, and
start, as on that plant, from the ends of the paracostal areolae
next the blade's primary midvein. In the mature leaf they are
more or less concealed in the segments' midribs. The areolae
between them, as in O. sensibilis, have the appearance of being

Narrow-Leaved Chain-Fern 141

stretched as the leaf becomes large, sometimes, the lower espe-
cially, to the vanishing-point.

Midveins are rarely evident in the lobes sometimes
present on the Blade's primary segments, but when evident
are formed in the same manner and start from such veins as
in O. sensibilis.

In the early leaves, the petiole, or at least its upper part, is
narrowly more or less winged laterally. Later the wings con-
tract, becoming mere ridges. The contraction apparently begins
below, extends upward, and involves the basal part of the blade ;
either before or soon after the formation of one or both of the
two basal primary lobes (whose midveins, if evident, would start
from the starting-points of the two basal paracostal areolae next
the blade's primary mid vein). These lobes thus apparently
are sometimes never formed and sometimes aborted early. The
parts of the blade that contain the two basal paracostal areolae
next the primary midvein appear to shrink into extensions of
the petiole's lateral ridges. The contraction finally involves
the wings between the blade's lower primary segments, these
wings also, in the sporophyll especially, becoming more or
less ridges.

In the transformation of the sterile leaf into a sporophyll
(Pis. XXXIX, XL, XLI), the entire blade contracts, and the
blade's margin recedes sufficiently to nearly reach the paracostal
areolae but not, as in O. sensibilis, sufficiently to cut them. The
effect produced is the same as if the part of the leaf-blade con-
taining most of the areolae outside the paracostal areolae had
been cut off the leaf, and the few veins remaining outside the
paracostal areolae had thus been rendered mostly free. The
veins forming the outer edges of the paracostal areolag become

142 Narrow-Leaved Chain-Fern

soriferous. The petiole lengthens, and both petiole and rachis
become stouter and dark-colored.

This fern is usually included in the genus Woodwardia, at
least in America, but appears sufficiently distinct to warrant
the restoration of Presl's genus Lorinseria, of which it is the sole
representative.

EXPLANATION OF THE PLATES.

PLATES XXXVII-XLI. — NARROW-LEAVED CHAIN-FERN. Lorinseria
areolata. Plate XXXVII. — 1-7. Young leaves and plants in different stages
of development, i. Young plant attached to prothallus. Plate XXXVIII. — i.
Mature sterile leaf. 2. Section of pinna of mature sterile leaf, X z\. Plates
XXXIX, XL. — Leaves intermediate between the mature sterile and fertile
leaves. Plate XLI. — i. Mature fertile leaf. 2. Section of fertile pinna,
X 2$.

PLATE XXXVII. — NARROW-LEAVED CHAIN-FERN

PLATE XXXVIII.— NAR:

•LEAVED CHAIN-FERN

PLATE XXXIX— NARRC

CHAIN-FERN

PLATE XL. — NARRO

EAVED CHAIN-FERN

r

EAVED CHAIN-FERN

CHAPTER XIX

SENSITIVE FERN

Onoclea sensibilis.

Rootstock wide-creeping, forking, greenish-brown to cherry-
colored, black in age, hollowed beneath bases of petioles, smooth
or bearing an occasional large pale-brown scale : leaves scattered,
borne on all sides of rootstock: roots copious, densely matted,
springing from edges of hollows, also often continued backward
or forward in lines from edges.

Leaves erect, dimorphous: the sterile twelve to fifty-four
inches long, leaf-like, sensitive to frost: sporophylls shorter,
contracted, rigid, paniculate, persisting into second season.

Petioles usually as long as or longer than blades, sparingly
furnished with pale brown, concolorous, hyaline, ovate, acute,
ciliate, often deciduous scales, at base similar in color and paral-
lel to rootstock, compressed, often elongate or cochleariform :
above erect, rounded; in sterile leaves slender, slightly furrowed
on face, green or in spring wine-red, straw-colored in age; in
sporophylls stouter, slightly flattened or furrowed on face, espe-
cially near the base, when dried greenish-straw-colored or in age
pale brown : fibrovascular bundles two, strap-shaped, uniting be-
low blade into one U-shaped in section.

Blades of sterile leaves deltoid or ovate-deltoid, below sub-

146 Sensitive Fern

pinnate or pinnate, above successively less deeply pinnatifid,
gradually or abruptly narrowing to the undulate or sinuate apex:
segments two to thirteen pairs, basal or second pair longest,
connected by a costal-wing or the lowermost distinct, lanceolate
or oblong-lanceolate, often narrowing both ways, the lower,
especially, narrowed at base, very minutely serrulate, the upper-
most otherwise entire or undulate, the lower more or less sinuate
or, especially the lowermost, deeply sinuous-pinnatifid ; the lobes
oblique, obtuse or a few subacute: apices obtuse or subacute:
rachis and midribs prominent beneath, smooth or bearing a
few minute, pale-brown, ovate or lanceolate, acuminate, ciliate
scales: surfaces glabrous otherwise, the upper grass-green; the
lower paler, slightly glaucescent: texture herbaceous.

Blades of sporophylls contracted, oblong, secund, bipinnate;
apex pinnate: pinnae bent backward and upward, appressed,
alternate or opposite, short-stalked or the uppermost sessile:
pinnules small, dark green, fleshy or cartilaginous, subglobose,
alternate or opposite, sessile or subsessile, reflexed, pinnatifid:
segments four to six, slender, oblong or deltoid, recurved and
connivent over sporangia, finally spreading apart, inferior basal
segment of pinnule often dichotomous: rachis when dried more
or less angled or grooved obscurely or partly subterete, glabrous
or sparingly chaffy as in sterile leaves.

Venation of sterile leaves conspicuous, pinnate, anastomose:
marginal veinlets largely free, simple or once forked: paracostal
areolae parallel or subparallel to costa, elongate, those next rachis
giving rise successively at ends to midribs of segments, those
next midribs to midveins of segments' lobes, in very narrow parts
of costal-wing contracted to vanishing point or veinlets forming
their outer edges alone visible, as fibres coherent with rachis:

Sensitive Fern 147

outer areolae much shorter, mostly oblong, hexagonal or pent-
agonal, oblique, or those nearest parallel or subparallel, to costa.

Venation of sporophylls pinnate, free, a simple or in forked
segments a once-forked veinlet occupying centre of each segment
of pinnules.

Sori medial on veinlets, blackberry-shaped: sporangia nu-
merous, borne on a cylindrical receptacle: indusia delicate,
whitish, coherent at inferior side of and partly surrounding each
sorus, opening toward apex of segment, at first almost completely
covering sori, later thrown back or torn, the sporangia becoming
confluent.

Spores very dark colored, ovoid.

Habitat. Grassy banks, roadsides, the outskirts of woods
and thickets, low-lying meadows, etc. In damp soil exposed to
the sun or partly shaded.

Range. Newfoundland to Saskatchewan, south to Nebraska,
Louisiana, and Florida.

Onoclea sensibilis. Linnaeus, Species Plantarum, 1062. 1753.

THE young plants of Onoclea sensibilis and Lorinseria areo-
lata are liable to be confused with each other, and before their
venation becomes anastomose, with Osmunda spectabilis Will-
denow,* but can be distinguished from the latter by the absence
of stipuliform appendages from the bases of the petioles, and
from each other by a difference in the shapes of their leaf blades.
The resemblance to the young plants of O. spectabilis is seen
only in the very first stages of development, is superficial merely,
and quickly disappears, but O. sensibilis and L. areolata are closely
related.

*The American species better known as Osmunda regalis, but separated from the
European species of that name by Willdenow.

148 Sensitive Fern

In O. sensibilis the margin of the sterile leaf-blade is very
minutely and obscurely more or less serrulate in all stages of
development. Aside from this, the blade is at first imperfectly
semi-orbicular, and sometimes obscurely trilobed, with sub-
truncate entire base and crenate or dentate upper margin. It
then becomes successively reniform or reniform-orbicular, with
undulate or crenate upper margin, reniform-deltoid becoming
crenately trilobed, and deltoid trilobed with deep often squarish
sinus at base. As development progresses, the central lobe be-
comes sinuate or lobed, and at length cut into segments, which form
all but the basal segments of the mature leaf and which, as they
develop, become in their turn undulate, sinuate, or pinnatifid.
The two lateral lobes develop into the basal segments of the
mature leaf and become sinuous-pinnatifid. At this stage the
segments above them range upward from sinuous-pinnatifid to un-
dulate or entire. Development of the sterile leaf as such then
ceases. Further change lies in its transformation into a sporophyll.

The veins are branched and free in the first stages of the
leaf -blade's development. They become anastomose before
a mid vein shows in any very distinct fashion. One or two
areolae form first in the centre of the reniform or reniform-
orbicular blade, and others quickly follow, forming outward
until the margin has the appearance of cutting the network of
veins. The marginal veinlets are mostly free.

When the blade becomes trilobed the areolae through the
centre of each lobe are straightened in such a way as to form
a double row, the inner common side of the two single rows
that make up the double one forming the midvein. There-
after every well-defined lobe or segment of the blade possesses
more or less of a midvein, similarly formed.

Sensitive Fern 149

The midvein of the central lobe of the trilobed blade is the
blade's primary midvein. As the lobe lengthens and is cut
laterally into segments, this midvein lengthens gradually and
becomes merged in the mature leaf's rachis.

The midveins of the two lateral lobes of the trilobed leaf,
since these lobes are the incipient basal primary segments of the
blade, are the two basal secondary midveins of the blade. In
the mature leaf they, as well as the midveins of the primary
segments later formed, become more or less merged in the seg-
ments' midribs.

The ends of the paracostal areolae next the blade's primary
midvein form the bases of the midveins of the primary segments.
The ends of the paracostal areolae next the midveins of these
segments form the bases of the midveins of the segments'
lobes.* Thus every paracostal areole next the rachis and
between midribs of the primary segments reaches from midrib
to midrib, and every paracostal areole next a midrib of a primary
segment and between midveins of the segment's lobes reaches
from midvein to midvein. As the segments grow larger and
the ends of these areolae are consequently drawn farther and
farther apart, these areolae appear to be stretched while the
rachis- wings containing them appear to shrink toward the rachis,
until, in the base of a very large blade, they are drawn out to
the vanishing-point and the veinlets that formed their outer
edges are more or less coherent with the rachis, if not contained
within it.

The transformation of the sterile leaf into a sporophyll can
be clearly seen from the transitional leaves which sometimes
occur (PI. XLV). In these, such parts of the blade's apical

* See page 119.

ijjo Sensitive Fern

section and primary segments as are not lobed already become
lobed, and contraction of the blade and recession of its margin
are begun and carried far enough to produce the following results.
The outermost part of the blade, containing most of the veins,
disappears; a few free veinlets, remnants of the innermost
areolae, are left next the lobes' midveins; the lobes are dis-
connected, narrowed, shortened, and recurved until subglobose,
finally splitting into segments and becoming soriferous; and
the contraction eventually draws the blade's primary segments,
now pinnae, backward and upward, and reflexes the subglobose
soriferous lobes, now pinnules. Indusia occur on the transi-
tional leaves as well as on the sporophylls.

The transitional leaves constitute the so-called "var. obtusi-
lobata" Torrey. As they represent merely the transition from
the usual sterile leaf to the fully fledged sporophyll, it is scarcely
necessary to say that to give them a distinctive name is absurd.

The affinity of this plant with Lorinseria areolata is marked.
Both plants are essentially akin in habit, have scattered leaves
rising from a creeping rootstock, sterile leaves similar in char-
acter and texture, and venation of the same type.

As already stated, in O. sensibilis development of the blade's
two basal primary segments is peculiarly rapid, while in L.
areolata contraction overtakes the corresponding part of the
blade at an early stage of the leaf's development.* This gives
different aspects to the early leaves of the two plants, but by
comparing the accounts of the development of their leaves it will
be seen that development, while carried further in O. sensibilis
than in L. areolata, is along similar lines in both.

The transformation of the sterile leaf into a sporophyll is in

* See page 125.

Sensitive Fern 151

both, aside from the production of sori, largely a matter of con-
traction of the blade and recession of its margin. The difference
in the venation of the sporophylls of the two is due to the fact
that in O. sensibilis the venation is more highly developed, since
midveins are evident in the lobes of the primary segments,
before transformation of the sterile leaf into a sporophyll begins,
and that the recession of the margin and the contraction are
carried further than in L. areolata.

It seems probable that if this contraction and recession were
carried in L. areolata, as in O. sensibilis, to the extent of cutting
the veins that form the outer edges of the paracostal areolae,
shortening the free veinlets thus formed, and so reducing' the
sori, which in L. areolata are borne on these veins, to a minimum,
the sori would present much the same appearance in L. areolata
as in O. sensibilis. In the leaves of O. sensibilis intermediate
between the usual sterile leaves and the sporophylls, in which
the contraction and recession have obviously been carried less
far than in the sporophylls, indusia of varying lengths are seen.
Some of these indusia are prolonged, extend along a vein, and
are attached to it by the upper margin, as the indusia are in the
sori of L. areolata; and it is apparently as the indusia shorten
in these leaves, approaching their form in the sporophylls, that
the line of attachment shortens and they become detached from
the vein everywhere but at the lower end, as they are in the
sporophylls. The indusia in these transitional leaves may be
vestigial sori, and the prolonged indusia may be evidence of a
time when the sori had the same form and were attached in
much the same manner in the ancestors of O. sensibilis as they
are in L. areolata.

This species is apparently very old. O. sensibilis fossilis

152

Sensitive Fern

Newberry * is said to differ from it only in possessing a more
robust habit. Specimens of the fossil fern are said to practically
duplicate both the mature sterile and fertile leaves of our fern,
and the transitional leaves as well. According to Dr. Knowlton,
the fossil fern has been found only in the Fort Union Beds at
the mouth of the Yellowstone, and in the Canadian Upper
Laramie.

*O. sensibilis jossilis Newberry, Ann. N. Y. Lye. Nat. His. 9 : 39. 1898. See
Lesquereaux, 111. Cret. and Tert. Plants, PI. VIII., Figs. 1-9, Figs. 1-5. 1878. New-
berry, Later Extinct Floras, 8: PI. XXIII., Fig. 3; PI. XXIV., Figs. 1-5. 1898. Knowl-
ton, Bull. Lon. Bot. Club. 705-706, PI. XXVI., Figs. 1-4- 1903.

EXPLANATION OF THE PLATES.

PLATES XLII-XLV. — SENSITIVE FERN. Onodea sensibilis. Plate XLII.
— i. Young plant attached to prothallus. 2-6. Young leaves in early stages
of development. Plate XLIII. — Young leaf in later stage of development.
Plate XLIV. — i. Mature fertile leaf. 2. Mature sterile leaf. 3. Section of
pinna of fertile leaf, X 2^. 4. Section of pinna of sterile leaf, X 2$. Plate
XLV. — Leaves intermediate between the mature sterile and fertile leaves.

PLATE XLII. — SENSITIVE FERN

n •

'•W^-C /\S - f ' ' SJ. 'I',' ;-''/,-

PLATE XLIII. — SENSITIVE FERN

PLATE XLV.-

•IVE FERN

INDEX

Adiantum pedatum, 33-39; unilateral ve-
nation in, 24, 25; explanation of odd
leaflet on rachis, 9, 35, 36.

Amesium, 30.

Asoidium ; acrostichoides, see Polystichum
acrostichoides; marginalis, see Dryopteris
marginalis; noveboracense, see Dryop-
teris noveboracensis; spinulosum, var.
intermedium, see Dryopteris spinulosa
intermedia.

Asplenium ; acrostichoides, see Athyrium
thelypteroides ; angustifolium, 63, 67,
diplazioid sori in, 66, 67, 72; ebeneum,
see A. platyneuron; ebenoides, 6; ger-
manicum, 30; platyneuron, 77-81, same
changes during its leaf development
under different conditions of environ-
ment, 7, 8, early stages of its leaf com-
pared with those of A. trichomanes, 73,
80; ruta-muraria, see Belvisia ruta-mura-
ria; septentrionale, 30; thelypteroides, see
Athyrium thelypteroides; trichomanes,
71-74, early stages of its leaf compared
with those of A. platyneuron, 73, 80.

Athyrioid sori, formation of, 103, 104; their
occurrence in the silvery spleenwort and
other species of Athyrium, 104; their
possible occurrence in any species of
Asplenium, 104.

Athyrium; acrostichoides, see A. thelyp-
teroides; cyclosorum, 104, 105; filixfcem-
ina, 104, 105 ; thelypteroides, 99-105.

Belvisia; the genus, 30; ruta-muraria,
27-30.

Camptosorus rhizophyllus, 131-134, early
venation of, 18, 133, auricles of the leaf
partly formed pinnae, 12, 133, 134.

Christmas fern, see Polystichum acrosti-
choides.

Crvptogramma Stelleri, 93-96.

Development of the fern leaf ; modes of,
1-26; in connection with different kinds
of venation, 9—25, see also Venation; in
given species, see chapters under species'
names ; retarded by low vitality of the
plant, 5, 6; set back by an injury to the
plant, 6; fluctuating in parts of flie leaf,
3, 4; affected by conditions of environ-
ment, 6, 7, 88, 89; carried beyond its
usual limits under certain conditions, 7,
88, 89, 115; supposedly specific characters
of the leaf sometimes features of only
certain of its stages, i, 115; mature stages

and stages at which sori appear, 4, 5; cer-
tain changes and the appearance and dis-
appearance of certain peculiarities in the
leaf indicating ancestral characteristics,
8, 9; monstrous, 26, in the maidenhair,
39, in the polypody, 50, 52, 53, in the
narrow-leaved spleenwort, 65, 66, in the
maidenhair spleenwort, 74, in the ebony
spleenwort, 81, in the hart's-tongue, 43.

Diplazioid sori, in the ebony spleenwort, 81 ;
in the narrow-leaved spleenwort, 66, 67;
in the silvery spleenwort, 100, 103-105.

Dryopteris; possible evolution of the ge-
nus, 105 ; acrostichoides, see Polystichum
acrostichoides; goldieana, 64 ; margina-
lis, 119-122; noveboracensis, 109, no,
its leaf-development compared with that
of D. simulata, no; simulata, 113-115,
found with Lorinseria areolata, 114, 139;
spinulosa intermedia, 125-128; thelypte-
ris, means of distinguishing it from D.
simulata, 115, its resemblance to Athy-
rium thelypteroides, 105.

Ebony spleenwort, see Asplenium platy-
neuron.

Flabellate venation, see Venation.

Hart's-tongue, see Phyllitis scolopendrium.

Lorinseria; the genus, 142; areolota, 137-
142, found with Dryopteris simulata, 114,
139, resemblance of its early stages of
leaf development to those of Onoclea
sensibilis and Osmunda spectabilis, 139,
147, its relationship to Onoclea sensibilis,
139, 147, 150, 151, its leaf -development
compared with that of O. sensibilis, 119,
150, its venation compared with that of
O. sensibilis, 140, 141.

Maidenhair, see Adiantum pedatitm.

Maidenhair spleenwort, see Asplenium
trichomanes.

Marginal shield-fern, see Dryopteris mar-
ginalis.

Massachusetts fern, see Dryopteris simu-
lata.

Narrow-leaved spleenwort, see Asplenium
angustifolium.

Nephrodium; marginale, see Dryopteris
marginalis; noveboracense, see Dryop-
teris noveboracensis; simulatum, see
Dryopteris simulata; spinulosum, var.
intermedium, see Dryopteris spinulosa
intermedia; thelypteris, see Dryopteris
thelypteris.

155

,56

Index

New York fern, see Dryopteris novebora-
censis.

Nephrolepis exaltata, 18.

Onoclea sensibilis, 145-152; its relation-
ship to Lorinseria areolata, 139, 147, 150,
151; its leaf-development compared with
that of Lorinseria areolata, 119, 150, 151;
resemblance of its early stages of leaf-
development to those of Lorinseria areo-
lata and Osmunda spectabilis, 139, 147,
change great in its transitional leaves, 5.

Osmunda, regalis, see O. spectabilis, 139,
147.

Pellaea; atropurpurea, 57-60, lobes of its
leaves partly formed pinna>, 1 1 , 12; gra-
cilis, see Cryptogramma Stelleri; Stelleri,
see Cryptogramma Stelleri.

Pinnate venation, see Venation.

Phyllitis scolopendrium, 43-45.

Polypodium vulgarc, 49-53.

Polypody, see Polyjxxiium vulgare.

Polystichum acrostichoides, 85-89; ap-
pearance of spinulose points on the leaf's
margin, 8, 9 ; leaf development exceeding
its usual limits under certain conditions,
7, 88, 89.

Purple cliff -brake, see Pellaea atropurpurea.

Scolopendrium vulgare, see Phyllitis sco-
lopendrium.

Silvery spleenwort, see Athyrium thelypte-
roides.

Slender cliff-brake, see Cryptogramma Stel-
leri.

Spinulose fern, see Dryopteris spinulosa
intermedia.

Unilateral venation, see Venation.

Venation ; anastomose pinnate, 12, de-
velopment of, 18, 19, in the walking-leaf,
132-134, in the narrow-leaved chain-
fern, 138-141, 150, 151, in the sensitive
fern, 18, 140, 141, 146, 148-151; free
pinnate, development of, 12-18, in the
.ebony spleenwort, 78-81, in the maiden-
hair spleenwort, 72-74, in the narrow-
leaved spleenwort, 64, 65, in the silvery
spleenwort, 100-103, m the hart's-tongue,
44, 45, in the purple cliff-brake, 58, 59,
in the slender cliff-brake, 94, 95, in the
Christmas fern, 86-88, in the Massa-
chusetts fern, 114, 115, in the New York
fern, 1 10, in the marginal shield-fern, 120,
in the spinulose fern, 126, 127, in the
polypody, 50, 52, 53; free flabellate, 12,
development of, 19-24, in the wall rue,
28-30; free unilateral, 12, development
of, 24, 25, in the maidenhair, 24, 25, 34,

37-39-
Walking-leaf, see Camptosorus rhizophyl-

lus.

Wall-rue, see Belvisia ruta-muraria.
Woodwardia, areolata or angustifolia, see

Lorinseria areolata.

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