Reserve food-materials in buds and surrounding parts

MEMOIRS

OF THE

ToRREY Botanical Club.

VOL. II.

•4 • ►

PUBLISHED FOR THE CLUB.
Sept., 1890 — Dec, 1891.

CONTENTS.

No. I.

Reserve Food-Materials in Buds and Surrounding Parts ( Plates I and
II). By Byron D. Halstead

Xo. 2.

Contributions to the Botany of Virginia. I. Notes on the Spring Flora
of Southwestern Virginia (Plates III and IV). By Anna Murray
Vail (with annotations b\- N. L. Britton, and a list of Mosses by
E. G. Britton. II. Notes on the Autumn FU^ra of Southeastern
Virginia. By Arthur Hollick 27-56

No. 3.

Contributions to the Knowledge of the Germination of some North

American Plants (Plates V-XIX). By TheodorHolm 57-108

Pages
1-26

No. 4.

The Genus Polygala in North America. By Wm. E. Wheelock,

109-152

MEMOIRS

OF THE

TORREY BOTANICAL CLUB.

Vol.' II. >^o. 1.

RESERVE FOOD-MATERIALS IN BUDS AND
SURROUNDING PARTS.

By Byron D. Halsted, Rutgers College, N. J.

The purpose of this paper is to consider the structure and
reserve food-contents of the buds and surrounding parts in
some of our trees and shrubs, with occasional reference to
nourishing substances as stored in other parts of perennial
plants.

Particular attention will be paid to starch, because this is
one of the most important constituents of the assimilated
food of plants, is stored away in a granular form and admits,
by means of its pronounced and characteristic reaction with
iodine, of being easily detected and definitely located in the
tissue bearing it.

Buds are the free extremities of branches, or, to place the
same idea in a different form, they are incipient branches,
whether located upon the free extremity or along the side of
a stem. In the former case they are called terminal, and in
the other lateral buds. As to their relation to growth they
may be active, that is undergoing elongation or branch
formation, or dormant, as illustrated by them in v;inter. It
is with these last that this paper will have most to do, for it is
in preparation for the inactive period that buds become most
highly developed, and their tissues charged with the nutritive
food-elements that are so much needed to push the plant for-
ward during the unfolding in spring. Buds are again divided,
as to their future development, into those that will produce
Vol. IL— I.

2

blossoms, called flower-buds, and those destined to grow into
ordinary stems, and to bear the foliage of the plant. One set
of buds become specialized, and are devoted to the particular
function of reproduction, while their neighbors continue their
growth and maintain the plant itself. The leaf-bud looks
only to the future of the individual, while the flower-bud
carries with it the idea of a new plant that in time is to
flourish separately. In external appearance the buds of various
trees and shrubs differ so greatly that they may well form a
part of a full description of any plant. It is not our purpose,
however, to go into any consideration of their sizes, shapes,
colors and other peculiarities. Those buds that are herein
treated have first of all a covering of scales accompanied by
more or less of a lining of fur, and frequently in addition a
varnish, all of which serve the important purpose of prevent-
ing access of water and the sudden changes of temperature
that might otherwise bring death to these seats of vitality.
The protective layers that a plant places over the tender sub-
stance of a growing point suggest the same provision for its
own safety when hard times come as do the thick, impervi-
ous coats that are wrapped round the germ of a future plant
as found ensconced in the seed. Within the bud-scales,
which may be few or m.any, thick or. thin, etc., there is the
point of growth now in a quiescent condition. It is somewhat
conical, possibly almost flat-topped, but from below it and
upon all sides there arise a number of lateral outgrowths, in
regular order, the youngest being nearest to the top, and these
curve upward and overtop the growing point. These greatly
disguised leaves are the first ones to unfold when the bud de-
velops into a stem, while at the same time new ones are pro-
duced in close proximity to the advancing point of growth,
thus continuing the bud as it pushes forward, leaving behind
a young stem with its developing foliage. In case of the
flower-bud, if it be one formed in autumn, as that of the apple,
peach and similar fruits, there are the same bud-scales, but
instead of a growing point that will develop into a branch,
there may be one or several miniature flowers which, when the
scales are thrown back, quickly open out into the fragrant
blossoms.

3

It is a matter of common observation that buds, and par-
ticularly those producing blossoms, open with rapidity, burst,
as it is termed, and there is no corresponding formation of
substance out of which to grow at that period in the life of
the plant. It follows, therefore, that there must be a reserve
of formative material stored somewhere in the plant for the
purpose of supplying the needed nourishment at this im-
portant and dependent annual period in the life of every tree
and shrub. If we should consider seeds as to their minute
structure, we should find that besides the plantlet there is
frequently a large mass of lifeless substance stored in contact
with the embryo, as in corn, and often enveloping it. This
liquifies in germination and yields to the unfolding plantlet
ample support until it can thrust its roots into the soil, lift its
fresh leaves up to the air and sunshine and shift for itself. In
many seeds, as the bean, the embryo is large and gorged with
the food-material that the parent plant has provided for it.

There are many points of agreement between a seed and
a winter bud. Both are constructed for a period of inactivity,
and protected from untoward influences by thick layers of
impervious substance. Both start into growth under the
same quickening influences of vernal warmth and moisture,
and in fact the buds of some plants, as those of the Indian
shot-lily, regularly become detached, fall to the ground and
are the starting-points of new plants. This is an important
point in proof of the similarity of structure of seeds and buds.
We should, therefore, naturally infer that at some place in
every bud, or near by, there is a reservoir of those substances
that are needed for its initial growth at least. A study of
this point is now before us."^

* The investigations, the results of which are herein presented, were begun
cUiring the winter of 1888-89, when, continuously for two months at the Iowa
Experiment Station, the reserve food-substances in apple-twigs were studied
in a score or more sorts, including a wide range of hardy and tender varieties.
The results as then obtained appeared in Station Bulletin No. 4, During
the past year, in spring, summer, autumn and winter, the work has been ex-
tended to include a large number of species of ligneous plants and the
roots of many perennial herbs.

4

STRUCTURE AND CONTENTS OF TERMINAL

BUDS.

The terminal buds seem the most natural place to begin
the consideration of the subject before us. In a greneral way,
in the introductory notes, the structure of these buds, situated
at the ends of shoots, has been pointed out, and it is for us
now to pass more deeply into the subject, and with the aid
of the microscope determine the minute anatomy of these
points of conservation of vital energy. As before said, the
leading component parts are the overlapping bud-scales pro-
vided with more or less hair and varnish, within which is
the bud proper, that is, the incipient shoot, bearing its leaves
as minute outgrowths which are arranged in a definite (acrope-
tal) order ; the large outer ones inclose the younger and
smaller ones, the central point of all being the extremity
of the stem. As in all newly formed vegetable tissue en-
dowed with the subtile power of further growth, the cells
that compose the central portion are small, thin-walled,
and their contents consist largely of that colorless semi-fluid
and extremely variable substance called protoplasm, the ac-
knowledged vehicle of vital activities. Below this cone of
delicate and almost homogeneous cellular tissue the stem is
seen to take its origin with the differentiation into the c}'lin-
der of wood cells and vessels, having upon its inner side the
comparatively unchanged pith, and, without, a thin layer of
active cells that is to continue the growth in size of the
branch by developing upon its inner surface new layers of
wood, while outside is produced a protective substance famil-
iarly known as bark. Therefore, by mentally combining
transverse and longitudinal sections of the base of a terminal
bud, the observer is able to determine the method of forma-
tion of the various elements that go to make up an ordinary
twig. The young leaves that are a part of the dormant bud
while still very small present but little more than the simple
cellular condition common to the short tip of the branch that
bears them. Among the outermost it is possible to distin-
guish'the details of form and outline, together with the vena-
tion and other points of differentiation determined by a micro-
scopic examination of newly unfolded leaves. Of course, the

5

distance to which this work of bud-growth extends, varies
greatly within and outside of the species, and is not a matter
to concern us farther at the time.

RESERVE FOOD-MATERIALS.

Plants which live from year to year do not use up all the
nourishment prepared by the green parts, principally the
leaves, during the season of active growth. They lay by a
portion of this material to be employed in the vital processes
at times when the plant cannot assimilate the crude sub-
stances which are obtained from the soil and the air. In short,
perennial plants, during the growing season, store some of
their elaborated substances in places where it becomes av^aila-
ble for nutrition in the early spring, while the plant is putting
forth its young twigs and leaves. This reserve material, as it
is termed, may for convenience be divided into two groups:
namely, those which are known as carbohydrates ; so called
because consisting of carbon and the elements of water, that
is, of carbon, hydrogen and oxygen, united in definite propor-
tions. The leading carbohydrate is starch, familiar to every
one as the basis of many foods for animals and man, as foimd
in potatoes, corn, and a long list of other vegetable products.
Oil- is another reserve form assumed by the carbohydrates,
and abounds in many seeds and other parts of plants. Sugars,
which by themselves make up a group of the carbohydrates,
are often found associated with the other forms of reserve
food-material above mentioned. There are other forms of
carbohydrates, but they do not specially interest us in this
paper.

The second division of reserve material, suitable for plant
nutrition, is known as albuminoids, so named from a resem-
blance to the albumen or white of egg. Protein is another
term given to the same group of substances, all members of
which agree in having nitrogen in their composition — a sub-
stance which is absent in the carbohydrates. They are more
complex and less stable compounds than the carbohydrates,
and are stored usually as amorphous contents of cells. Some-
times, however, they assume the form of grains (aleurone), or
crystal-like bodies (crystalloids), and in these condensed condi-
tions may be met with in seed, like beans and peas, which are

usually rich in the albuminoids. The proteids are the basis of
protoplasm, and protoplasm is the substance which is inva-
riably present in every living cell. As protoplasm is the
complex compound in which life always manifests itself, the
importance of the albuminoids out of which protoplasm is
made, becomes self-evident.

Doctor Vines, in his new work," in treating of the repose
of the above compounds, says: "When once deposited the
reserve materials undergo no change, or, at most, the proteids
may slowly undergo some alteration, so long as the organ in
which they are deposited remains in an inactive condition.
An organ in this state is practically dead for the time being,
all its metabolic processes being arrested. It is capable, more-
over, of resisting injurious influences, such as extremes of
temperature and desiccation, which would prove fatal to it,
were it actively living. It is obviously in consequence of this
property possessed by such organs during wdiat we may term
this state of suspended animation, that vegetation is main-
tained in regions in which the cold of winter is severe, and in
arid tropical regions. The time of the possible duration of
this state, without permanent loss of vitality, varies very
widely." It is well known, for example, that some seeds retain
vitality for a long time, especially starchy ones. With the
quickening influences of warmth and moisture supplied by
spring-time, the reserve materials undergo changes which con-
vert them into substances that can readily travel to seats of
vital activity when they are employed in growth.

Starch. — Returning to the carbohydrates, they will be
taken up in the order of their importance. The test for
the detection of starch is the very satisfactory one of iodine
solution, which turns this substance blue, while it fails to pro-
duce the same color in other cell contents. By means of this
reagent, starch is found quite generally at a short distance
below the growing point, and usually in the form of compound
granules, the component parts of which separate quite easily.
These masses, or compound granules, vary greatly in size, and
the smaller particles of starch do not exhibit this compound
nature. Starch-bearing cells of well-matured twigs may con-

* " riiysioloj^yof Plants," l8S6, p. 172.

tain hundreds of these granules, when they are completely
filled with the nearly spherical masses.

The relative position of the starch varies greatly with dif-
ferent buds, especially in widely separated species of trees
and shrubs, but in those that are well matured, upon the same
plant, there is a fair degree of constancy.

At this point it is necessary to state that there are two
classes of terminal buds, so called, among ligneous plants,
with some gradations betw^een them, not a little confusing.
There are those which are characteristic of plants, with a well-
defined habit of growth, that is, those that lengthen their
shoots for a definite period, as in the horse-chestnut, for ex-
ample, and then spend the balance of the growing season in
forming a large terminal bud, and supplying it with nourish-
ing food for the next year's development. On the other hand,
there is a large group of trees and shrubs, and especially
brambles, that grow on indefinitely, produce no plump, ter-
minal bud for winter, usually kill back, and therefore must
start the farther elongation of the twig from some lateral bud
perhaps a foot or more back from the end of the stem. It
is needless to say that the remarks to follow obtain only
with the first class, and the consideration of the second will
appear later, because less simple.

In order to make a careful, microscopic study of the cell
elements of a terminal bud, it is necessary to secure several
thin sections with a sharp razor, made in various directions
through the bud. One of the most satisfactory is made length-
wise through the middle of the bud, and from this the posi-
tion of the food-elements, after a little experience, can be
determined with a fair degree of accuracy. This is said, not
to discourage the making of horizontal sections, which are
necessary for the demonstration of some important points, but
to facilitate the work of those who may choose to extend the
investigation herein outlined.

Figure i shows such a section through the terminal bud of
an apple-twig, made in February, 1890, and therefore during
a remarkably warm winter. The feature to be first observed
is the dark column in the lower center (a) of the figure. This
is the pith of the subadjacent stem, the cells of which are

8

starch-bearing; this fact being indicated by the darkness in im-
itation of the color produced in this part of the section by a
sohition of iodine. At b and c are the scars of the last two
leaves of the previous season, and from them pass inward and
downward the vascular tissue that gives elasticity and strength
to the twig. Other similar but smaller vascular threads are
seen above, receding from the bases of the bud-scales, and
uniting into a cylinder of woody tissue, still in a formative
condition. The remaining part of the bud consists of small,
many-sided cells packed together, a large number of them
bearing complex, sphere-shaped crystals of oxalate of lime,
while others are filled with semi-solid substances composing
an impure form of protoplasm. The feature of most interest
in this connection is the sharp line separating the starch-bear-
ing cells of the pith from those in the younger pith just above,
in the contents of which starch is entirely absent. There is
a definite localization of the starch, as a rule, in or near all
terminal buds that are fully matured. In those gathered be-
fore the processes of growth are completed, the starch maybe
scattered in all parts of the soft tissue, and especially in that
portion lying between the zone of wood and the rind.

Besides the presence of starch, there is another marked
difference between the pith indicated by the shading and the
younger portion above, containing the albuminoids and crys-
tals. The latter, it has been said above, is composed of thin-
walled cells, and not materially different from those in all
other parts of the bud. But the starch-bearing cells have
their walls much thickened, and in such a manner that canals
are left extending from the original cell wall to the free inte-
rior. These canals of adjoining cells meet at the juxtaposed
walls, so that provision is thus made for the ready transfer of
material from one part of the storage tissue to any other. In
figure 2 is shown a portion of the tip of the starch-bearing pith
in the terminal bud of a Duchess pear, and the adjoining thin-
walled pith. At this line, which is usually somewhat convex,
the tissue will often give way in making the sections, leaving
the firm, thick-walled pith with a ragged edge. A few of the
starch-bearing cells, highly magnified to show the details of
their canaliculate structure, arc shown in figure 3.

*

9

In making a longitudinal section of a terminal bud with a
sharp knife, the operator quickly learns to detect the starch
pith as soon as it is reached in the downward passage of the
instrument. The bud proper is cut with ease, but there is a
sensation known to grafters and others as that of " grittiness,"
which is due to the resistance to the knife caused by the many
thick walls of the starch-bearing cells. This is one of the
most important modifications of the ordinary cell wall, and
consists of a thickening due to the intercalation into it of a
substance called lignin, which chemically differs somewhat
from cellulose, and adds materially to the hardness and dura-
bility of the tissue lignified. This power of resisting external
influences is gained, however, at the loss of much elasticity.
Lignified cells do not abound in protoplasm, but water passes
freely through their walls. All permanent, inactive tissue
may become lignified, and when this process is freely carried
out it yields the durable heart-wood so familiar in many kinds
of timber. The subject is of interest because it helps to ex-
plain the matter of grit," or " grittiness, "so frequently spoken
of by those who cut the twigs of various sorts of fruit-trees.
The inflexibility of tips of certain plants is due in most parts
to the large amount of lignin their pith contains.

The free end of a mature twig consists of a cone of mi-
nute, thin-walled cells, upon the outside of which the small,
imperfect leaves, as bud-scales, arise in regular order, and,
overlapping each other, enclose the tender growing point of
the twig. From the scales, bundles of fibers and vessels de-
scend and form a thin ring of wood around the pith just below
the growing point. At this portion of the twig the pith
makes up the greater part of its substance. In short, the bud,
the stem, and for a quarter to a half inch below it, are com-
posed of soft tissue, easily crushed with the thumb and finger.
But below this the large central pith is particularly rigid, due
to the unusual thickening that has taken place in the walls of
the cells. If the reader will bear in mind that the wood zone
is very thin at the upper part of the twig, and that the bast is
almost wanting, it will be evident that the pith alone must
give the rigidity found near the extremity of matured twigs.
From the shape of the nearly spherical cells it follows tnat
Vol. II.— 2.

lO

there can be no very great toughness. Contrariwise, brittle-
ness characterizes the upper portion of a well-matured twig,
and for two or three inches below the terminal bud it will
often snap, almost like a pipe-stem, when sufficient side
pressure is applied.

Sugars. — Tests for other carbohydrates were made, princi-
pally the various sorts of sugars. Grape sugar was gener-
ally present in variable quantities in all terminal buds. Cane
sugar and dextrine w^ere likewise present in most cases, but in
small quantities. Grape sugar was most evident near the
growing points, and cane sugar, if it appeared at all, was in
the fine, unlignified tissue at the base of the bud. In view
of the fact that starch is readily changed into sugar within
the plant, under conditions similar at least to those sur-
rounding the twigs when gathered for testing, it follows that
sugar, which in this connection may be considered as another
term for soluble starch, would be expected, and in variable
quantities. Twigs gathered directly from trees also show ed
these sugars in small amounts.

Albuminoids or Proteids. — This group of complex and very
variable substances does not readily admit of separation into
individual sorts, and is therefore treated as a whole. Proteids
are present in all living parts of ligneous plants, and are most
abundant near the points of greatest vital activity. In the
apple, for example, there is little or no albumen in the pith
at the base of an old twig, very little in the wood zone, an
abundance in the cambium layer, and the largest percentage
in the buds. In these last places, when the buds are mature,
the albuminoids make up a large part of the cell contents, to
the exclusion of the starch. All the varieties studied exhib-
ited the albuminoids as brick-red particles when treated witli
the Millon test, a nitrate of silver compound, described else-
where. On account of the conspicuous color the presence of
the protoplasmic compounds is easily demonstrated. When
the tip of a twig was still soft, spongy and without rigidity
from a failure of the pith to lignify, there was only a feeble
response. Protoplasmic matter was present, but so scattered

* The methods obserx'cd in the iiiicro-phytochemical study of these car-
bohydrates will receive separate treatment at the close of the paper.

II

over a large area of cellular tissue that no distinct line or
point of coloration developed, as is true of buds which have
become ripe.

The albuminoids, therefore, like the starch, from their be-
havior in green and ripe twigs, become a test of maturity.
These complex compounds are the ones out of which proto-
plasm forms, and afterward renews its strength. They are
the most important reserve materials in the sense that they
stand, in composition, nearest to that of protoplasm, which is
the acknowledged vehicle of vital activities. It is not unnat-
ural that these compounds, in a resting twig, should be stored
in the buds where they are to be needed the coming spring.
Starch may, therefore, be excluded from a well-equipped bud,
because other substances of greater consequence, and accumu-
lated in smaller quantities, are conserved at the points of
growth. In other words, there is a manifest tendency for the
concentration of reserve materials at points where they are
to be used, and in the order named ; first the albuminoids,
and next the carbohydrates — first the basis of protoplasm,
and next the substance protoplasm must use in the building
up of new tissue, and in other vital processes. Following
upon this is the conclusion resulting from the investigations,
namely : that, other things remaining the same, the best-con-
ditioned twig is the one having a sufficient amount of reserve
material within easy reach, and in the best condition for the
use of the plant. A well-preserved bud is therefore plump
with reserve substance in a comparatively solid condition,
being firm but not woody ; is well protected from the injuri-
ous effects of very sudden extreme changes of temperature,
and has close at hand a sufficient amount of starch, or other
carbohydrates, for its most advantageous development.
Whether one form of bud, as to its length, breadth and thick-
ness, color or number, and hairiness of scales, may be better
than another under any special condition, is a question more
likely to be determined by field trial than by laboratory tests.
Plants, seemingly equally hardy, may have the vital points
very differently constructed. No matter along what line the
problem has been worked out by the species, the chief point
is to prepare for hard times, and having once made the prepa-

12

ration remain quiescent until the coast is clear for another
year of growth. The inherent tendency of one introduced
variety of plant to start into growth before another ma}^
throw it into the class called tender, while another with the
sanae structure, but differently disposed, will prove hardy.
The test for sugar in the late winter may aid in deciding
that a difference in this tendency exists, for starch, the chief
form in which the carbohydrates are stored up in many kinds
of twigs, is changed into sugar before it becomes available for
plant nutrition.

Crystals. — A few words concerning these structures, which
were constantly met with in all buds examined, will be suffi-
cient for this portion of the subject. Vegetable physiologists
are agreed that true crystals (not including crystalloids) in the
tissue of plants are a form of refuse, or left-over matter, re-
sulting from the processes of growth, and put up in a consoli-
dated form, to get them as much out of the way as possible.
Some one has compared them to the pieces of brick, mortar
and other material thrown into boxes and barrels during the
construction or repair of a building. Crystals were rarely
found in the old pith, and have not been seen in the wood, but
are very abundant just below the growing tips of all buds in
that cylinder of tissue connecting the free extremity of the
bud with the starch-bearing cells — a half-inch or so back of
the tip. The loose green bark of all parts of the twigs also
abounds in these bodies, and they are especially numerous in
the cellular tissue that lies between the leaf scar and the bud
above it. In this locality, a second form is often met with,
which is smaller and rectangular in shape, while the prevail-
ing sort is an irregularly spherical aggregation of sharp-
angled bodies, which have taken the name of spha2ro-cr\\stals.
These crystals are composed of oxalate of lime (calcium ox-
alate) and may be dissolved by mineral acids.

From the composition of these bodies, their universal
prevalence in about equal numbers, first in proximity to tis-
sues which are the centers of rapid vital processes, and sec-
ondly, in out-of-the-way places, and for various other reasons,
it is safe to conclude that crystals are no safe criterion by
which to judge of the relative resisting powers of plants to

13

the untoward influences that may surround them. One would
as soon think of deciding upon the stability of a house or
bridge by the number of chips that the builders have made.

Tannin. — Like crystals in vegetable tissues, tannin is con-
sidered as refuse matter, and not, with perhaps certain excep-
tions, further active in the vital processes of the plant. Tan-
nin, as recognized by salts of iron, is abundant in twigs, and in
transverse sections is found most common in the rind, and the
inner bark close upon the cambium, anS between it and the
zone of bast. There is a great difference in the amounts of
tannin between the several species. The buds contain more
than the other portions, and in immature terminal buds the
tannin is quite generally diffused throughout all parts of the
soft tissue.

COMPARISON OF VARIOUS SPECIES.

The reader is now prepared to make a comparative study of
the food-materials in the terminal buds of some of our leading
kinds of trees and shrubs, confining his attention for the pres-
ent to those with well-developed buds at the extremities of
the branches. In the horse-chestnut we have a typical illus-
tration of buds with large and therefore conspicuous parts.
A longitudinal section is made with great ease, and there is
noticeable absence of the grit found in many twigs. The
pith is very large, and at an inch or so below the bud it is
dry and filled with air. The starch deposit occupies a thimble
or nipple-shaped portion of the moist pith, above which is
the growing point with its proteid compounds. Instead of
growing for a long distance at the least expense and strength-
ening the upper portion by a deposit of lignin in the pith, the
wood zone continues of considerable thickness, and the buds
rest in tliis ring as a crayon is held by its handle or clamp.
Figure 4 illustrates these points better than can be described
in words. The small amount of starch present may be diie to
the warm winter, for the varnish was much softened at the
time of gathering (February 20), and the moist (almost wet)
pith was filled with a mixture of the soluble carbohydrates and
the albuminoids ready for the initial growth.

In remarkable contrast with the last are the clusters of

buds at the ends of twigs, as in the cherry, oak, etc. The
tip of the twig is enlarged ; the wood zone is thin, but there
is a corresponding lignification of the great mass of pith,
thus giving stabiHty to the end of the shoot and furnishing a
reservoir for a large supply of starch from which the several
buds can draw liberally when they need this nourishment.

The maples offer a case of buds being in pairs, and there-
fore there are three very near to the extremity of the twig — the
terminal or central one and two lateral buds, in the hard
maple {Acer saccJiartnn, Marsh.)the disposition of the starch sug-
gests a thimble or a finger of a glove, it forming a narrow layer,
in the pith that lies next to the thin zone of wood. In the soft
maple {Acer saccJiarinuni) the thimble has no tip, but is like a
glove finger " that has been cut off near the end. This may-
arise from the fact that the lateral buds are not so close to the
terminal one.

The ashes are like the oaks in having a large amount of
starch near the terminal buds. On the other hand, the catalpa
resembles the soft maple in having a " thimble."

In the locust we have an illustration of a poorly formed ter-
minal bud, and the starch distribution is accordingly peculiar.
The treatment of such cases comes more properly under the
head of lateral buds, but they form a transition between the
terminal and lateral. The starch of the upper two inches of the
twig is distributed quite equally between the two buds either of
which might receive it all. In the basswood there is much
the same condition of things, and in the hackberry also.

Among shrubs the lilac is a striking example of copious
starch-storing at the tips of the branches, but in this case it
should be remembered that two large buds are located ter-
minally and two shoots must be provided for instead of one.
Figure 5 shows the quite constant condition of the shrub in
winter, and as this plant has been studied throughout the year
it will be treated of elsewhere.

The garden cherries have terminal clusters of buds as in the
oak, only larger, but the amount of starch is small. The same
is true of the wild cherries. However, a large amount of gum
or mucilage is present, and this doubtless serves the same
purpose as starch in the economy of the plant.

15

Plums have much more tapering twigs, and end in minute
terminal buds, but with considerable starch located in a cone
of lignified pith, as has been mentioned for the apple and pear.
In the peach'the terminal bud is large, but the starch is much
less abundant than in the pear and apple ; it is midway between
the pear and the cherry in respect to its starch-bearing, and
perhaps holds the same position as to the amount of mucilage
or gum*.

There are many species of trees that do not usually present
any starch in the twigs of the last year's growth, among which
are the various kinds of willows and poplars, but the older
wood of the main branches, as a rule, contains more or less of
this food substance. Among shrubs the elder and currant and
gooseberry have but a smaM amount of starch in the vicinity
of the terminal buds. In short, there seems to be no evident
rule to guide one in the matter. Starch may be in abundance
in one species when least expected and almost absent from
another.

Other Carbohydrates. — An explanation of the absence of
starch in many twigs is not far to seek. It may be due first to
the substitution for it of oil, as in many seeds as well as buds
and twigs. The pine family is a striking illustration of this,
in the buds and branches of the members of which a pitch
abou^nds, largely to the exclusion of starch. Sugars of the
various sorts in like manner may take the place of starch in
furnishing the carbohydrates needed for the growth of plants.
In the second place, starch may have been deposited, but
afterward changed into those closely related chemical com-
pounds that, being soluble in cell sap, are ready for transporta-
tion and work. Rarely does a mature bud not respond to the
Trommer and Fehling tests, but those without starch in their
vicinity indicate the largest amounts of the soluble starches,
as they are sometimes called. In this connection it may be
said that the wood of the common currant bush was thoroughly
examined because of a failure to find starch in the young
twags. When the roots, however, were tested, it was found
that they abounded in starch. Albuminoids and sugars were
present in the ends of the twigs, while the storehouse of starch
was below ground.

i6

LATERAL BUDS.

In general structure the lateral buds closely resemble the
terminal ones, but are much smaller, and have -a somewhat
different attachment to the twig. The soft cone of small cells
rests upon an abbreviated stem from which the outer scales
arise. Where the bud is connected with the twig there is an
interlacing ring of fibers and vessels, and within this is a cen-
tral pith, which is modified as spoken of while treating of the
terminal bud ; that is, the cells are very thick-walled, having
undergone the process known as lignification, a characteristic
of the durable parts of most ligneous plants. As the lateral
buds are often close to the twig upon one side there is a con-
sequent lack of symmetry. The exposed surface naturally has
a greater development of the protective la\ ers, the bud-scales
being both thicker and more numerous upon the outside than
next to the stem. There is also more of the red coloring
matter in the exposed parts. Over all parts there may be a
coating of soft down consisting of colorless hairs which grow
from the epidermal or outer layer of cells of the bud-scales and
the body of the twig. As the twig matures this hairiness is
quite easily removed, so that its presence or absence in mid-
winter is largely accidental.

Flowcr-Buds. — As a general thing, the conditions that sur-
round a flower-bud are necessarily much the same as those of
the leaf-bud. Both are incipient branches, and while one is
destined to elongate into a twig, bearing ordinary foliage, the
other remains comparatively short and produces disguised
leaves for the purpose of reproduction. It is true, however,
that while the leaf-bud soon becomes self-supporting, and in
fact finally makes the starch for the next season's use, the fruit-
bud is a source of loss to the plant, and therefore needs to be
provided with nourishing food-materials. On this account it
is natural to expect that the fruit-buds should be specially
favored in the location of starch and albuminoids.

Flower-buds usually are not strictly terminal, that is, at
the extremities of main twigs. However, there are excep-
tions, and the treatment of flower-buds does not fully fall
under either of the two groups of buds already considered.

17

Thus in the peach the flower-buds are not at the ends of the
shoots, but instead are here and there along the twig in the
position of, and easily distinguished from, the lateral leaf-buds
by their larger size, extreme hairiness, etc. Not infrequently
there are three buds at a node and raised upon an abbreviated
spur, but in such cases the central one is a leaf-bud, and the
two lateral ones each contain a flower. The apple, in some-
what the same manner, has lateral spurs, at the end of which
is a bud containing three or more immature blossoms appa-
rently terminating the branch, but in fact only overreaching
a dw^arfed leaf-bud situated somewhere among them.

In the horse-chestnut is an illustration of the center of the
large terminal bud being occupied by a flower-cluster which
when unfolded is a foot or more in length, and bearing pos-
sibly a hundred blossoms. This flower-cluster, at first ter-
minating the stem, soon takes a lateral position by the devel-
opment of a leaf-bud that continues the twig.

A large number of flower-buds have been examined dur-
ing the past winter, both to determine the disposition of the
reserve substance and to make notes of the influences of the
warm weather. As far as the storage of starch, sugars and
albuminoids is concerned, it can be briefly stated that there
is no material difference between the fruit and the leaf buds,
except that the latter are usually larger, lack the light green
interior, characteristic of the young parts of leaf-buds, and con-
tain within and near them a greater supply of the albuminoids,
backed up by a lignified starch-bearing tissue. Not being
strictly terminal, the fruit-buds are well located for the immedi-
ate storage of starch in the wood and pith of adjoining parts.

In the fruit-buds of the peach there is an interesting case
of the special localization of starch that has not been found
in those of apple, plum, cherry, quince, or in fact any other
blossom-buds subject to examination. Without entering into
a description of the peach blossom, it may be said that there
is a single pistil centrally located, about which the other parts
are disposed — the calyx as a cup bearing the stamens upon its
inner surface. In figure 6 a peach-bud is seen in longitudinal
section, with its upper part of fuzzy bud-scales removed, ex-
posing in the center of all the pistil a, and next the stamens b.
Vol. II.— 3.

i8

All of the base of the bud c is charged with albuminoids
and carbohydrates that do not respond to the starch test.
When the wood, d, of the twig is reached, it is found filled
with starch, as indicated by the shading. Near the base of the
pistil, or miniature peach, is a triangle of starch-bearing
tissue. Occasionally, starch is also found in the pistil and the
stamen-filaments. These last need to undergo rapid growth
at time of blossoming. Whether this starch was stored in
these parts, far away from the great reservoir of this material,
during the growing season, or has been laid down afterward,
is a question that is not answered. It is, however, a well-known
fact, that starch can be deposited, then dissolved, and re-
deposited in another place repeatedly within a short time
when such a change of the carbohydrates is of advantage to
the plant. A study of the formation of the callus, and of the
knitting tissues of grafts, is interesting in this respect. It is,
however, true, that when the flowers develop the reservoir at
the base of the peach pistil becomes emptied of starch, and
the tissue, not being thick-walled like ordinary starch-bearing
cells, is similar to that around it.

TRANSVERSE AND LONGITUDINAL SEC-
TIONS OF TWIGS.

An ordinary twig of the last season's growth consists of
the following parts : (i) A central cylinder of pith which runs
the whole length, ending at the tip in the terminal bud. This
pith consists of many-sided cells, which are about as long
as broad, and packed so closely together as to leave but
few cavities, called intercellular spaces, between them. The
cells nearest the center are usually largest, and the outermost
smallest, and have the thickest walls. (2) Next outside of
the pith is a ring or zone of wood, which is very thin at the
upper end of the twig, but gradually becomes thicker as the
basal end is approached. This wood consists of long ducts
or vessels running longitudinally in the twig, and surrounded
by slender, thick-walled flexible wood cells. The wood is the
most substantial part of a twig, and makes up the greater
part of any tree. In the wood ring of the twig are thin
plates of pith-like cells, which reach from the pith to a thin

19

belt of cells, capable of growth, situated just outside the
wood, and called the cambium layer. These plates of thin-
walled cells, known as the medullary rays, are here especially
mentioned, because they play an important part in the stor-
age of the reserve food-substance formed by the plant during
the growing season, and stored away to be employed during
the initial growth in early spring. Besides the vessels, wood
cells and medullary rays in the wood ring, there are also
long, rectangular starch-bearing cells, in m.any respects not
unlike the pith, extending lengthwise of the wood, and at right
angles to the general direction of the medullary rays. These
may be styled the wood-pith cells. (3) The cambium layer,
above mentioned, is made up of small, thin-walled cells, and
constitutes the soft layer at which the wood and bark may be
separated, especially in spring. The radiating plates of pith
cells which reach from the pith to the cambium layer, and
above designated as the medullary rays, project beyond the
cambium, and broaden out in the loose, cellular part of the
bark that lies between the somewhat interrupted ring of bast
and the cambium. (4) This bast is the tough fibrous part of the
bark, and consists of small bundles of thick-walled cells which
run lengthwise of the twig, and are usually midway between
the rind and the cambium. (5) Upon the exterior of all is
a double layer of thick-walled cells. The outer may be styled
the cuticle, and beneath this is a much thicker layer of firm
tissue, with the contents of many of the cells colored green.
The outer and thinner layer bears much of the coloring mat-
ter which gives mature twigs their characteristic reddish,
brown or other color. Between the rind and the ring of bast
is a belt of loose, cellular tissue abounding in cavities between
the cells known as intercellular spaces. This is the loosest
tissue in the twig, and may be called the pith of the bark.
It, however, differs from the true pith in the center of the
stem in having the cell contents colored green. It is often
and appropriately called the green bark, and is the part ex-
posed when the thumb-nail removes the rind of a twig but
does not pass deep enough to reach the wood layer.

Tiierefore, to recapitulate, the twig in cross-section consists
of the following parts, beginning at the outside : A double

20

rind or protective covering of thick-walled cells more or less
impervious to water, and bearing the matter which gives the
twig its color. Within this is a broad. loose belt of green cells
and large intercellular spaces which reach to the tough fibrous •
band of bast. Succeeding the bast, passing inward, is an-
other loose belt of cellular tissue narrower than the one out-
side the bast into which the medullary rays project as they
pass through the cambium layer. Next, within this cam-
bium, is the wood with its medullary rays which reach to the
central cyhnder of pith. The outer portion of the pith, the
medullary rays, and the pith wood-cells at right angles to the
latter, are the three portions of the internodial part of a twig
that are starch-bearing. The above description considers only
sections that might be made through the twig at any point
between the buds. At the nodes or points where lateral buds
are developed there are certain modifications of the structure
which have been considered.

JUNXTURES. — At the point of union or junction of two
years' growth of a twig, as of that found during 1889 and that
of 1890, there are but few structural features not included in
the description of the twig already given. The point is easily
determined from the outside, for the scars of the several scales
of the terminal bud of the previous ytar remain to mark the
place, which is somewhat larger in cross-section than the twig,
an inch or so abo\'e and below, it. It also is a starting-point
from which the buds become more distant, proceeding either
up or down the twig. If these points are not sufficient, the
brighter, fresher red of the more recent growth will be quite
sure to distinguish the place of union. With a cross-section
of the twig under the microscope, the age in years is quickly
determined. The first wood formed on a yearling twig in
spring is more porous than that last produced the previous
autumn. It is on this account that the wood of an old branch
is arranged in evident rings, and if there has been no interrup-
tion in the growth of the plant during any summer there will
be a ring for each year, the thickness and porosity of which
will vary with the season's favorableness for growth. Micro-
scopig inspection of the juncture does not reveal any very
marked modification of structure. The cylinder of pith is

2 r

larger here, often twice the normal diameter of that just above
or below : its cells are smaller and thicker-walled and inclined
to be elongated and arranged in longitudinal rows, as if to
add rigidity to this portion of the twig during the early spring
growth, and give general stability at a point where elements
of weakness naturally obtain from the union of the wood of
two different years. Below the juncture the pith contains a
cone or thimble, the outer cells of which are usually tinged
with brown as if dead, and in shape and position it accords
with the exterior of the lignified pith which has been men-
tioned as beginning a short distance below the base of the
terminal bud. With certain chemical reagents and coloring
materials this thimble or cone of pith, surrounded by struc-
turally almost identical tissue, behaves the same as that at the
top of a well-matured twig, and easily met with by cutting
down through the terminal bud lengthwise with a razor or
sharp knife. It is evident, therefore, that as the terminal bud
undergoes development in the spring, the soft thin-walled cells
at its base become lignified, and while they are finally appa-
rently the same in structure as the cells below them which
were lignified the autumn before, the line of separation is not
obliterated, but instead may be usually observed, without
the aid of a magnifier, by making a longitudinal section
through the juncture.

The point that most interests us in this connection is the
important part which the juncture plays in the storage of
reserve material, and especially starch. Having become
adapted for this service while situated in the vicinity of the
terminal bud, the lignified pith cells continue for several years
in the same capacity, and probably at no time become entireh*
free from these substances. Trees and all starch-bearing
shrubs exhibit this fact, but some much better than others.
For example, the pear is shown in figure 7 as a type of the
large class of trees. Figure 8 is of the honey locust, which is
without a well-formed terminal bud, and the branch is each
year continued by a lateral bud. Twigs with opposite buds,
which, of course, from what has been seen of the relation
between buds and starch storage, have the amount of food-
reserve doubled at any one transverse plane of'the node, are

22

illustrated in the ash. figure 9. In the lilac, as before men-
tioned, there are practically two terminal buds, and this leads
to another form of juncture shown in figure 10.

Some extremely slow-growing horse-chestnuts and ailan-
thus trees, found in a rocky situation near New Brunswick,
N. J., present striking illustrations of the point in hand, be-
cause what is usually found in a twig of several feet in length
is condensed into as many inches. The ailanthus, figure ii,
illustrates the method of killing back of the tip each year,
and the renewal from a lateral bud. In fact, everything has
gone so irregularly that the storage of starch at the junctures
is far from uniform. In the y^sculus, figure 12 a, the case is
ver\^ different, and the progress, although small, is quite uni-
form. Looking at this twig from the outside, there is one
almost continuous display of bud-scale scars, so that the age
of the branch could be determined only with much difficulty.
On the other hand, by splitting it through the middle, the
empty, thin-walled, colorless sections of pith are quickly seen
as alternating with those of a brownish tinge. But the great-
est difference is manifest when half of such a twig is laid for
a few moments in a dish containing iodine, and afterward
washed in alcohol. It is then that the blue sections of pith
are seen to correspond to the basal part of each successive
terminal bud, and the enipty pith separates them. The
starch-bearing cells in the y^sculus are not as much lignified
as in most twigs, and for this reason, when they lose their
normal amount of moisture by exposure, will shrink, leaving
depressions in the pith channel at these points, while the
empty, colorless pith between them retains its plump form
indefinitely. An examination of a similar yEsculus stem,
made July 30th, showed that only a small fraction of the
starch still remained, and with almost none in the bud itself.
At b, in the same figure, the parts of a rapidly grown, long
horse-chestnut twig are shown in contrast with the slowly
developed branch at a.

SPINES AS RESERVOIRS OF FOOD.

A study of the winter contents of the thorns of honey
locust, hawthorns, wild crab-apple and the Japan quince, etc.,

23

leads to the conclusion that these sharp means of defense serve
another purpose, perhaps only secondary, besides that of pro-
tection. Upon examination for starch, it was found that
there was an unusually large per cent, in the thorns. A thorn
of a honey locust, for example, when examined in midwinter
is found to consist of a horny exterior, within which is a dry,
somewhat powdery, snuff-brown mass, containing no starch.
Near the base of the thorn at that place where it is sometimes
flexible in its attachment to the stem, when growling, for ex-
ample, upon the bole of the tree, the central pith is firm
throughout, of a greenish color when freshly cut, and packed
with starch. In figure 13, at a, is shown a longitudinal sec-
tion, through such a thorn. It is also seen by the same figure
that the starch diminishes rapidly in amount, passing upward
from the thorn, while below it remains of about equal amount
until the lower of the series of buds below each spine is
passed.

The position of thorns being near the bud favors the
idea of their serving as places for the storage of starch, for
when thus laid away for the winter it is close at hand for
use when the growing days of spring arrive. The relative
amount at the base of the spine, and below at the point bear-
ing the buds, is shown in the cross-section b, and not only is
there more within the stem at the juncture of the spine, but
the base of the latter is more thoroughly gorged than any
other part of the tree. At c is a section shown midway of
the internode.

In the hawthorns the structure of the base of the thorn is
somewhat different. Omitting the discussion of the minute
structure of the spine it will be sufficient to call attention
here to figure 14, in which the starch, the darkened portion, is
seen to occupy the pith of the twig, making a V-shaped
structure at the base of the spine. In addition to this, there
is a somewhat triangular starch-bearing portion above and
below the pith of the base of the spine. In some specimens
the starch extends for nearly a half-inch into the spine, but
as a slender point.

In the wild crab (Pyrits coronaria, L.), the spine is more like
an ordinary branch, because usually bearing buds upon its

24

exterior, and has the starch-bearing pith extending for a half
of the way, from the base to the sharp, hard tip. In the
naain twig there is a manifest accumulation of starch at the
base of the spine, as is shown in figure 15. Figure 16 shows
a fruit-spur, the center of which is filled with starch for the
purpose of providing abundant nourishment for the develop-
ment of the cluster of flowers.

Many other examples might be cited, but that of the
Japan quince (Cydonia Japonica^ Pers.) will suffice. The spines
of this favorite hedge plant were examined in February, while
some of the blossoms had already expanded, due to the very
warm winter of 'Sg-'go. The position and relatfve size of the
parts are shown in figure 17. It will be seen that the flower-stem
is short, and the spine joins it at the base. In figure 18 the
condition of the starch storage becomes clear. There is no
starch in the flower-spur, but an abundance in the interior of
the spine, to be withdrawn to feed the flower and the leaves
that afterward come upon the stem.

It is very likely that the spines are primarily for the
warding off of enemies, but if we can look upon the protective
organs as serving another purpose it adds further dignity to
the police department, so to speak, of the plant.

METHODS AND REAGENTS.

Starch. — For the detection of starch, as before stated, the
solution used was iodine made as follows: three grammes of
crystallized potassium iodide were dissolved in sixty c. c. of
distilled water, to which was added afterward one gramme of
metallic iodine. This solution was diluted as the occasion
required. The microscopic inspection for starch was with
thin sections either treated at once with the iodine solution
or after they had received potassic hydrate to remove the
protein compounds that might otherwise obscure the reaction.
When the presence of starch was established its abundance
and general distribution was determined by splitting the bud
or twig, or both, and immersing the parts for a few minutes
in a h)ng porcelain trough, when the degree of darkening of
the various parts of the section gave the amount of starch

25

present. By removing the twig to a bath of alcohol for a
minute the subject was cleared up, and the location of the
starch-bearing portions could be made out more distinctly.
If desired, thin sections could be taken from the treated sur-
face for microscopic study.

Sugars. — The sugars of various sorts are usually associated
with each other, and only the presence or absence of the group
was usually attempted. Trommer's test is a simple and satis-
factory one : Place the slices or sections in a porcelain dish,
add a strong solution of cupric sulphate and heat to boiling.
Wash the specimens thoroughly, and add hot potassic hydrate,
when the presence of dextrine and grape-sugar will be shown
by a reddish precipitate. To separate these two sugars, treat
the original tissue to alcohol, standard strength, for a few
hours, which will dissolve away the grape-sugar, when the
dextrine can be tested for as before. Cane-sugar, with Trom-
mer's, gives a bright blue color in the cell contents, quickly
vanishing, but no red precipitate. It is well for the student to
make tests with this reagent of vegetable tissues containing
large quantities of each one of the leading kinds of sugars.
Fehling's solution, which is a modification of the above, may
be employed. In place of the pure cupric sulphate solution,
one of one part of the cupric sulphate and five parts of potas-.
sium sodium tartrate in eight parts of water may be used.
This reagent needs to be kept in the dark.

Albuminoids. — For these MiUon's reagent w^as employed.
This is prepared by adding to metallic mercury an equal
weight of concentrated nitric acid. When all is dissolved add
twice the volume of pure water. Place the tissue in a porce-
lain dish, add a little of the reagent and heat, when a rose or
brick-red precipitate indicates the presence of albuminoids. A
dark yellow, with nitric acid, and a yellow or brown with
iodine also indicate the same substances.

Crystals. — There are two leading salts in the form of
crystals in plants, the carbonate of lime and the oxalate.
The crystals having been detected with the microscope, acetic
acid may be added, which will dissolve the carbonate with
effervescence, but does not act upon the oxalate.

Tannin. — The various iron salts give with tannin a very

26

dark color, therefore ferric chloride may be employed for its
detection.

LiGNIN. — Carbolic acid dissolved in concentrated hydro-
chloric acid gives a green color with lignin, and hydrochloric
acid and alcohol develop a beautiful rose color after some
hours.

The works most frequently consulted for methods in the
studies contained in this paper have been " Behren's Guide to
the Microscope in Botany," by Hervey, and Goodale's
Physiological Botany." Upon the general subject much
assistance can be obtained from " Sach's Vegetable Phy-
siology," Vine's Physiology of Plants," and " Strasburger's
Das Botanische Practicum." The most elaborate paper con-
-^ulted is a " Memoire sur la Moelle des Plantes Ligneuses,"
with numerous elegant plates, by A. Gris, in " Nouvelle
Archives du Museum d'Histoire Naturelle, 1870.''

Rutgers College,

July 2 1 St, 1890.

MK^^()1RS TORRKV P.OTAXTCAL CLU15. PLATE \.

MKNfDlKS TORRKY r.OTAXICAI. i'lX W. Vl.Al K li.

Photocopying is not
recommended

V