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ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3

VOLUME VI

ILLUSTRATIONS

Acer saccharinum, 11
Amelanchier canadensis, 19

Arnold Arboretum as seen from an Airplane, 39
Arnold Arboretum Pit House, Interior view, 55
Crataegus Arnoldiana, 27

Facsimile of the Title-page of Mascall’s Treatise on Grafting, 51
Hedera helix baltica, 3, 5

Hemlock Hill, Demonstrating the Effect of the Recent Fire, 23
Finns pungens, 13
Poncirus trifoliata, 47

Primus maritima. Distribution of (map), 41
Rosa rugosa kamtschatica, 31

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI MARCH 29. 1932 NOS. 1 &2

Baltic Ivy {Hedey'a helix var. haltica), one of the Arboretum’s
introductions, has remained for twenty-five years in modest re-
tirement on the south wall of the Administration Building. Among
the millions of visitors who have come and gone during that time
hardly one has noticed the plant, read its label or realized that it was
in any way remarkable. There is nothing unusual in its appearance.
The leaves are scarcely different from those of the common English Ivy
and even in the technical characters studied by botanists there is little
to set it apart. What is remarkable about the Baltic Ivy is its resis-
tance to cold weather. It is hardier than any other true Ivy which
has been tried out at the Arboretum and is for this climate, the quick-
est growing.

Baltic Ivy was discovered by the present curator of the Herbarium,
Alfred Rehder, on one of the trips he made to Russia when preparing
the Bradley Bibliography for the Arboretum. He found it growing as
a ground cover in the pine woods near Riga, in what is today the re-
public of Latvia. Since this was outside the known range of the com-
mon Ivy, and in a region of very cold winters, he not only collected
specimens for the Herbarium but arranged with his host, Baron von
Sivers, to have living plants sent back to the Arboretum.

The plants sent by the Baron arrived safely in 1907 and in the twenty-
five years since that time they have grown into a solid mantle of green
reaching well above the second story windows. They look, as has been
said, much like any other Ivy except that they do not become badly dis-
colored during cold weather. Perhaps their most noticeable character-
istic is the variation in leaf size, some of the sprays bearing small, dark-
colored, conspicuously-veined leaves, while on others the leaf is virtually
the size and color of the common Ivy. As a consequence the general
appearance of the whole vine is somewhat irregular and unkempt.

In the last two or three years the appearance of the vine has altered
remarkably for it has begun to flower and Ivy is one of those interest-
ing vines in which the fruiting branches look very different from the

1

2

rest of the plant. Two other vines introduced by the Arboretum have
this same curious habit of becoming quite different in their old age;
they are the Wintercreeper (Evonymvs radicans) and the Climbing
Hydrangea (Hydrangea petiolaris). The change from youth to ma-
turity is even more striking in the case of the Ivy as can be seen from
the plates which accompany this article. It is hard to believe that
these two forms, the juvenile climbing form, and the branching adult
form, could belong to the same variety; superficially they look as
th3ugh they belonged to different species or even to different genera.
Certainly they are more different than a branch from an apple and one
from a pear. Yet they came from the same vine. The first plate shows
the vine as it appeared during the first 20 years of its life and as it
looks even now on its lower branches. This is the so-called juvenile
form. The other plate shows branches which have been flowering and
fruiting for the last three years. The more carefully these two plates
are compared, the greater does the difference between the two forms
appear to be. The juvenile form is unbranched; the fruiting one branch-
es again and again. The juvenile form is a vine clinging tightly to
trees or walls by numerous small roots. The fruiting branches are
stiff and erect; even when the Ivy is grown on a wall they project out
at right angles, giving somewhat the effect of a small bush grafted on
top of the vine. This effect is heightened by the arrangement of the
leaves which instead of occurring in two neat parallel rows as they do
in the juvenile shoots, are borne on all sides of the stem. The leaf
shape differs as well, the leaves are narrow, pointed at the basal end,
and unlobed.

This transformation is indeed as remarkable as that from Dr. Jekyll
to Mr. Hyde but it is by no means as reversible. When once the change
from youth to maturity has occurred it is permanent. Year after year
the fruiting branches grow out farther and farther away from the wall
or tree on which the vine is growing. New fruiting branches appear
until the whole top of the vine is one continuous bush. The lower
part of the plant may continue to send out vine-like branches but none
of these originate from the fruiting wood. Even when cuttings are
taken from the fruiting branches and they are grown as indepen-
dent plants they seldom lose their shrubby character. Instead of a flat,
quick-growing vine they produce a shrubby, slow-growing shrub, similar
to the fruiting branch from which it came but not at all reminiscent
of the original vine. It is, therefore, possible to grow each species of
Ivy in two entirely different forms, the climbing juvenile one and the
arborescent fruiting one. These ivy bushes, technically know as “var,
arborescens'' are seldom if ever seen in this country but in England
they are very common, particularly in gardens which were laid out
during the Victorian era. During that period Ivy enjoyed its greatest
popularity. Nurserymen responded to the general demand and many gar-
den varieties made their appearence. There were yellow-leaved,
white-leaved, and even red-leaved forms. There were varieties which
had leaves with deeply lobed edges, and others with neat scallops. There
were short, thickset dwarfs and arborescent fruiting forms of many of
the varieties. Some had round leaves, others triangular leaves, several
long and halberd-shaped leaves. Whole books were published

J

/

Hedera helix var. baltica (Juvenile form)

4

about the Ivy. Exhibitions of fancy Ivies were held and in some cases
entire K^i’dens were })lanted with fancy-leaved Ivies and Hollies. The
climbing forms, each one different, were |)lanted one after another
along walls in the background and specimen plants of fancy-leaved
Hollies and arborescent Ivies were set out in front of them, spaced
well apart in neat beds.

The multiplication of these garden forms and the natural variability
of the Ivy have combined to make identification of garden Ivies exceed-
ingly difficult and in some cases next to impossible. There are five
recognized species of Ivy native to Europe, Asia, and North Africa.
Each has given rise in nature to geographical varieties which depart
somewhat from the type of the species. All of the known species and
many of their geographical varieties have been introduced into cultiva-
tion and many of them are grown both in the arborescent form and in
the juvenile form. Finally in addition to all these “natural” forms
there are the fancy-leaved freaks which have originated in cultivation.
They now number between fifty and one hundred varieties and belong
to three of the species, though most of them are forms of the com-
mon Ivy {Hedera helix).

This confusion is twice confounded by the fact that even the wild-
growing species have very few precise differences by which they can
be distinguished. Only one really reliable technical character has been
discovered, the hairs on the stems and leaves. Ivy, to the naked eye,
seems smooth and shiny; one would never think that it bore any hairs
on the stem or leaf. But a closer examination will reveal numerous
tiny gray flecks along the stem and on the young leaves. At the ends
of vigorous branches these flecks sometimes become larger and more
numerous until the whole end of the branch seems almost scurfy.
Seen under a hand lens, these flecks ar e found to be hairs, but hairs of a
very peculiar sort. They have a very short stalk and branch out in
star-like fashion so that the whole hair is umbrella-shaped or shield-
shaped. By these tiny hairs the species can be quite readily distin-
guisned. In some species the rays are long, in others they are short.
In some the rays are seperate, in others they are united. One of the
differences between Hedera helix and its variety baltica is that while
in the former there are only five or six rays to a hair, the latter us-
ually has eight. The differences between the species are even more
extreme, as is shown in the accompanying plate. Figures 1 and 2 show
greatly enlarged views of the hairs of Hedera helix var. haltica. Above,
at the left, is shown the far different hair of Hedera colchica. It
will be seen that the hair from the Baltic Ivy has fewer rays and that
they are spaced widely apart instead of cohering into a disk.

Nearly all the cultivated Ivies seen in this country belong to one
variety or another of the English Ivy {Hedera helix), of which Mr.
Rehder’s Baltic Ivy is merely a hardy northern variety. Unfortunate-
ly many of the garden Ivies introduced into cultivation in this country
have been chosen from among the more tender varieties such as Hed-
era helix var. poetica, and the Scotch or Irish Ivy {H. h. var. hibernica).

Hedera helix var. baltica (Fruiting: branch)

6

With a little care in searching out the hardier sorts we ought even-
tually to be able to grow Ivies in our New England gardens almost
as readily as they are grown in northern Europe.

The Baltic Ivy is not the only variety which has proved hardy at
the Arboretum. A semi-climbing form which came in under the name
of Hedera helix var. arborescens, has made a good growth and withstood
winter injury. A large-leaved Ivy {Hedera colchiea var. amurensis)
from Kew Gardens has proved fairly hardy though it is scarcely an
attractive plant. More promising than either of these is a hardy form
of the common Ivy from Switzerland brought back to this country
many years ago by a member of the Agassiz family and recently ob-
tained for the Arboretum from the Leyland Estate in West Manches-
ter. As it grows on the Leyland estate it is somewhat protected from
extreme cold by the nearby ocean and it has grown out in great pro-
fusion, covering the southside of the house and the garden walls and
fruiting heavily each year.

Last September an attempt was made to combine the hardiness of
these two strains, the Baltic Ivy and the the variety from Switzerland,
by hybridizing them. Strong, healthy flower-branches of the Arbore-
tum vine were selected as the mother parent. Working from ladders and
window sills, the buds were opened with small steel forceps and the
pollen sacs were removed. A trip was made to West Manchester for
flowering branches of the Swiss Ivy. These were kept in the laboratory
and as the flowers opened and shed their pollen it was carried outdoors
and applied to the waiting stigmas. Soon afterwards the seed pods
started to swell; the cross had been successful. All during the winter
months the pods have continued to enlarge, for Ivy, strangely enough,
ripens its dark blue berries between September and May. The seeds
are now nearly ripe. If they can be germinated successfully and ij
the hybrid seeds grow, and if the seedlings are not accidentally des-
troyed, the Arboretum may hope, in a few year’s time, to present
American gardens with an even hardier and more vigorous variety than
the Baltic Ivy. Until that time, the Baltic Ivy is to be recommended
for northern gardens.

Edgar Anderson

EXPLANATION OF PLATES
Hedera helix var. baltica (Juvenile form). Figures 1 and
2, greatly enlarged views of stem hairs, seen from above.
Figure 3, a single hair oi H. colchica for comparison (after
Tobler). {Drawing by Blanche Ames Ames.)

Hedera helix var. baltica (Fruiting branch). Below at
the left an enlarged cross-section of a single berry, showing
two ripe seeds and an aborted ovule.

{Drawing by Blanche Ames Ames.)

7

Spring Classes for 1932. Three types of classes for amateurs are
being offered this spring at the Arnold Arboretum. One, a course in
the identification of trees, is being given in connection with the Scout
Masters’ Training School and is already well under way.

A series of informal walks will be offered to the general public dur-
ing April and May. On Saturday afternoons, a member of the staff
will meet interested visitors at the Forest Hills Gate at 2 o’clock and
conduct them on an hour’s walk around the Arboretum, lecturing on
the various trees and shrubs which are then in flower. No charge will
be made for these walks which will be held, weather permitting, on
the following Saturday afternoons: April 30th, May 7th, 14th, 21st,
28th, and June 4th.

The third series is in the nature of an experiment, which if successful
will be conducted on a larger scale next year. It has seemed that
many people might like to visit the Arboretum during the long spring
evenings and study some particular group of plants in which they are
interested, under the guidance of a member of the staff. Any group
of ten or more people with such an objective may apply for this priv-
ilege. They may be a garden club, or a scout troop, or a group with
no formal affiliations, but willing to come on the same evening and
study the same subject.

The Arboretum will make every effort to cooperate with such visit-
ing groups in making their visit worth while. If for instance, they
wish to study the pruning of shrubs, a demonstration will be arranged
for their benefit. It may be possible to arrange an indoor lecture
later in the evening, if this is desired. The weekday evenings in the
last four weeks of May will be set aside for this purpose and an en-
tire week will be reserved for each organization. The meetings will
be scheduled for Monday or Tuesday (at the pleasure of the visitors)
with the understanding that if the weather is inclement the meeting
will be held on the next possible evening up to and including the fol-
lowing Friday. The four weeks which are offered for such study visits
this spring are May 9th, 16th, 23rd, and 30th.

Past experience with scout troops and garden clubs has taught us
that an amazingly high percentage of organizations make arrangements
for visits to the Arboretum and fail to appear at the time appointed.
For this reason the Arboretum requires a deposit of ten dollars at the
time the reservation is made. When the organization visits the Arbor-
etum on the scheduled week the deposit will be refunded. If the ap-
pointment is not kept, the deposit will be retained at the discretion of
the Arboretum. The Arboretum is always willing to serve the public
but it does not wish to waste its efforts.

Eugak Anderson

8

“Winter Browning” of Conifers. In early spring, before there is
any external evidence of growth, coniferous foliage often exhibits a
rather sudden browning. The extent of the browning varies from a
touch here and there to extensive patches or an inclusion of the entire
crown, in the last instances the plants appearing as though dead. This
injury is most pronounced in the foliage produced the preceding year
though it may extend to needles of all ages. Not infrequently twigs
as well as the leaves may be killed outright. No species are wholly
immune, whether of Pines, Spruces, Firs, Arbor vitae, etc., but some are
more susceptible than others. There are, also, differences in liability of
individuals of the same species. Browning occurs almost exclusively
on the sunned side of the crowns, and in the case of trees is most severe
in the lower branches. The actual damage done varies chiefly accord-
ing to the amount of twig-killing. If there is nothing more than a
browning of the foliage, the subsequent new growth restores the green
aspect of the crowns, and little permanent injury results. If twigs are
killed there is a dwarfing of branches on the southerly exposed sides
and in most severe cases plants may be killed outright.

The cause of “winter browning” has been ascribed by some observers
to excessive loss of moisture at a time when the ground is still frozen
and the roots are unable to make good the losses, and by others to
frost-killing of leaves and twigs, the cells of which have begun to be
active. As “winter browning” takes place at a time of the spring
when periods of warm sunny days are often followed by frosty spells
the two explanations are not wholly incompatible, because it is a fact
that transpiration, or the giving off of water from a plant, is not simply
evaporation but is a process dependent to a great extent on protoplas-
mic activity in the cells. It is quite conceivable that excessive tran-
piration without restoration of the water content would result in harm
to the living substance. However, the second one is the more explicit
and is backed up by a certain amount of experimentation. Neger, a Ger-
man pathologist, exposed spruce branches to eight or ten degrees (Cen-
tigrade) of frost in freezing mixtures for a few days and then micro-
scopically examined the tissues of needles of different ages. He found
that there was a frost injury and that the killing was greatest in the
youngest needles and progressively less in the older. When branches
treated in this way were exposed to the sunlight the browning developed
just as in nature.

Avoidance of browning is desirable, especially in the more tender
shrubs. This can be provided by temporary shelter or protective plantings.

J. H. Faull

Washington Elm. (Supplement to Bulletin No. 18, 1931.) In our
Bulletin of Popular Information on December 10, 1931, we pub-
lished our doubts upon the authenticity of some grafts now being
offered by nurserymen as descendants of the Washington Elm in
Cambridge. It has been brought to our attention that the Arnold
Arboretum itself took some part in the identification of the tree on the
grounds of the Public Library at Wellesley from which these grafts
were taken and on whose descent from the original Elm their authen-
ticity therefore depends.

For this reason, and because the Arboretum did itself once accept
the identification, it does not wish to be understood as in any way
impugning the good faith of the nurserymen who now rely on it.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI MAY 6. 1932 NOS. 3&4

Some Early Flowering Trees. The flowers of many of our earliest
blossoming trees are unrecognized by a great proportion of the people
who enjoy their beauty of foliage or shade. Inconspicuous flowers
may be followed by more or less noticeable or showy fruits but these,
too, sometimes attract little notice.

While we have Witch-Hazels earlier, the first of the large trees,
native or foreign, to blossom in New England is our White or Silver
Maple {Acer saccharinum). Normally flowering about the middle of
March, in the past exceptionally mild winter the first flowers were
found fully open on January 14th on a large low-branched tree in the
Arboretum. This tree has been watched and noted in the early spring
for a good many years and its flowers always appear more precocious
than those of other trees of the same species in the vicinity. Not all
of the flowers appear at the same time, some remain in bud during a
cold period succeeding the opening of the first flowers and develop the
rest of their flowers several weeks later. Because of freezing, the
earliest may not produce fruits but some of the later blooms may do
so. In this latitude the fruit usually ripens in the last days of May or
the first days of June. We have records of ripe fruit on May 18th.

The Maple most nearly associated, botanically, with the native Silver
Maple is our Red or Scarlet Maple (Acer rubrum). This usually does
not blossom until about the middle of April when its honey-yellow or
scarlet flowers cause the trees to have a much more conspicuous as-
pect than is ever shown by the White Maple. The fruits of the Red
Maple are often as conspicuous as the flowers and mature with those
of the White Maple. They are about one-fourth the size of those of
that species, the wings often being brightly colored. If the seeds are
allowed to become very dry they soon lose their vitality or power of
germination. In nature the seeds germinate soon after falling on
moist ground, so that new plants are well developed during the same
season in which they are produced. The little plants of the White

10

Maple are generally much larger than those of the Red Maple of the
same age. Male and female flowers are usually produced on separate
trees but, occasionally, both may be found on the same tree.

In this region about the middle of April is the normal time for our
American or White Elm {ULmus americana) to blossom. These flowers
usually appear when the Red Maple blooms, but the dates may vary
according to season. The little flat, winged fruits ripen at the end of
May. Young plants 2 or 3 inches high should be developed in the same
summer that the seeds are produced. An interesting peculiarity of the
seedlings is that the first true leaves they produce are opposite while
the normal phyllotaxy or leaf arrangement in later growth and in ma-
ture trees is alternate.

Alders and Hazels in various species, were in best flower early
in April and the bloom is now over for this season. A careful
examination of a flowering branch of Alder {Ainas) will show the
fading male catkins at or near the tips of the branches while in-
conspicuous female or pistillate catkins are near them on separate stems.
While in New England we usually think of the Alders, such as Alnus
incana and A. rugosa, as being coarse shrubs, they may become small
trees. There are truly arborescent species native on our Pacific Coast.
An Asiatic species, Ainas japonica, is quite hardy in this latitude and
may become 60 or 70 feet tall. The Hazels are also commonly regard-
ed as shrubs but the European Hazel or P’'ilbert {Corylus uvellana) at-
tains a height of 15 or 20 feet, while the Turkish Hazel {Corylus col-
urna) will, under favorable conditions, become a shapely tree 60 or 70
feet in height. Like the Alders, the Hazels are monoecious, producing
male aments and female flowers on the same plants. While the stam-
inate catkins show conspicuously at or near the ends of the twigs, the
pistillate flowers are developed from lateral scaly buds, only the pistils
being visible at time of inflorescence. These female flowers develop
into the well known hazel-nuts or filberts, partly or sometimes wholly,
surrounded by leafy husks or involucres.

The Poplars are distinctly among our early flowering trees. They
are dioecious trees with the male flowers usually making a more con-
spicuous show than those with pistillate catkins. The proximity of
male trees near dwellings may be the cause of much “dust” appear-
ing on furniture while they are in bloom. A few weeks later the pistil-
late or fruiting trees may cause annoyance by the abundance of “cotton”
which, at maturity, floats through the air, often in great profusion.
This “cotton” is made up of innumerable, very slender, white, silky
hairs which escape from the opening pods or capsules. These silky
hairs are attached like parachutes to the very small seeds and enable
them to attain a wide distribution through wind agency. Planters of
the commonly used Poplars are confronted by annoyance from the pol-
len of the male trees or later by the escaping ripe seeds from the fruit-
ing trees. Where only one or the other of the sexes will satisfy the
ends desired, usually for quick growths or for screens, it is perfectly
practicable to select that sex which will cause least annoyance. Plants

2

Acer saccharinum

12

may be easily grown from cuttings, a mode of propagation hardly feas-
ible with most of our desirable shade trees. Probably the most com-
monly employed of these Poplars are the Cottonwood {Popitluff buham-
ifera), the Canada Poplar {P. canadensis) which is regarded as a
hybrid between P. balsamifera and the European Black Poplar, known
botanically as P. nigra, and its variety P. nigra italica, the Lombardy
Poplar. Many of the Poplars are crossed by hybridization, either
naturally, by wind-transported pollen, or occasionally by the interven-
tion of man. Therefore there may be many puzzling forms found in
cultivation or in nature.

Our Quaking Aspen (Popiilns tremuloides) and our Large-toothed
Aspen (Populus grandidentata) are among the earliest of the Poplars
to blossom, the precocious flowers appearing in the first days of April
in some early seasons, but being subject to delay until the middle of
the month or later if the season is cool. In the popular mind some of
the Willows are acclaimed as the earliest of our trees to flower and
indicate the approach of spring, but usually the announcement of
early bloom merely indicates the bursting of the scales covering the
buds and exposing snugly packed catkins covered with fine, silky,
white hairs attached to the small scales which subtend the numerous
little flower buds found in each catkin. The swelling and splitting
of the bud scales and exposing of the silky hairs may occur in early winter,
during a mild period, two or three months before pollen and stigmas are
matured. Hence the earliest of the Willows cannot be classed as real-
ly in flower before the Poplars. The most precocious species are merely
shrubs and commonly blossom in early April, the arborescent species
not generally flowering until the latter part of the month or later.
Like the Poplars, the Willows are dicecious. Generally they are easily
propagated by cuttings. If plants are desired for their pretty catkins,
male plants will prove the most desirable as the anthers are more
showy than the pistils.

Observation of our Conifers will show a number of genera and
species which produce flowers very early in spring. The Larches are
among the largest of our Conifers which flower in early spring before
much development of new leaves. They are monoecious, the male
flowers being usually short, button-like or globose, borne on the sides of
the branches, while the female flowers appear less numerously as small
cones than the male flowers. The bracts of the cones are often bright
red or scarlet.

Arbor-vitae {Thuja occidentalis) was in best blossoming early in
April in some localities and in some of its numerous forms. The
flowers are among the smallest of those of our native hardy Con-
ifers, averaging only about an eighth of an inch in diameter.
A careful examination is necessary to discover the little purplish male
flowers and the greenish female blossoms. The latter appear as swol-
len tips nearer the end of the twigs than the males. Another native
tree with flowers even smaller than Arbor-vitae is the White Cedar
of our swamps {Chaynaecyparis thyoides) which usually produces its
tiny male and female flowers in abundance on the same branches in
early April.

PiNUS PUNGENS

14

In the latitude of Boston our Red Cedars {Juniperus virginiana) are
past, their fullest bloom being in April. This group is usually dioec-
ious, at flowering time the male trees being most conspicuous with the re-
lease of vast quantities of yellow pollen, the female trees seem-
ingly flowerless but a close examination shows little pale green cones
which develop into the characteristic small fleshy blue fruits.

The Yews also blossom early. They are commonly dioecious, so
that if raised from seed only a part of the plants would produce the
conspicuous red fleshy fruits characteristic of this genus. Any partic-
ularly desirable form is usually propagated from cuttings.

During the past two weeks Magnolia stellata and M denndata have been
in good flower although somewhat injured by late frosts. Prunvs Ar-
meniaca is flowering well this season, and Forsythias, Spice-bush
{Benzoin aestivale) and Leatherwood (Dirca palnstris), often mention-
ed in these Bulletins, were in their best flowering condition about
April 27th. The single flowered Japanese Cherries are just passing
out of bloom and the double flowered Cherries are now the most attrac-
tive feature in the Arboretum. Although there have been some in-
juries, the mildness of the past winter was, on the whole, favorable
for plants so that, unless there are severe late frosts, the trees and
shrubs should develop an attractive and interesting show of flowers.

J. G. Jack.

Flowering Habits of Trees and Shrubs. Most trees and shrubs bloom
in the spring, but the flower buds may be formed and often are well
developed long before the blossoms appear. In the Rhododendrons
and Azaleas the young flower buds are formed in early summer. In
August and September the pollen mother cells divide to form the young
pollen grains. These develop and the flower bud is well formed and
easily recognized in the fall. The buds remain dormant during the
winter but complete their growth and blossom in late spring or early
summer.

A more usual type of floral development is that found in the Apples.
The flower buds are differentiated in July, but make little growth until
the following spring. During the fall and winter they cannot be ob-
served without dissecting the surrounding tissue. Development is re-
sumed in the spring and the pollen grains are formed in late April or
early May. The flowers open several weeks later.

A third type of floral development is found in the Larch. In the fall,
the pollen mother cells begin to develop and show the early stages be-
fore division, but further growth is suspended until February. Growth
is resumed periodically during the few warm days of late winter, and
in March the divisions which form the pollen are completed. These
cell divisions occur even when the snow is on the ground and the day
temperatures are little above freezing.

The Conifers vary greatly in time of pollen formation. In Yews
and Junipers the young pollen grains are formed in the fall. The

15

Hemlocks and Pines show little flower bud growth until spring The
pollen is formed in April or early June. Some species form their pol-
len in the fall while other species in the same genus show little floral
development until spring. Cornus mas, C. jiorida, and C. kousa all
have well developed buds with young pollen grains in the fall, while
Cornus stolonifera does not produce pollen until May. Cornus was,
the Cornelian Cherry, completes its floral differentiation in the fall and
is ready to bloom early in the spring. This year it was one of the
first shrubs to bloom and was out several weeks before the Forsythias.
Cornus kousa and C. jiorida are much later in time of flowering,
although their buds are also well developed in the fall.

Most trees and shrubs differentiate their flower buds in the summer
even though the pollen is not produced until spring. This condition is
found in the Apples, Hawthorns, Quinces, Viburnums, Cherries, Maples,
Magnolias, Honeysuckles and Lilacs. The flowers which appear on these
trees and shrubs were set last summer and the number of flowers
which will develop was largely determined by the conditions last year.
The abundant rains of last summer should insure prolific flower pro-
duction this spring, especially where the plants are properly cared for,
as they are in the Arboretum.

Next season’s flowers are influenced only by climatic and cultural
conditions but can be increased by proper pruning of certain plants.
In the Rhododendrons and Lilacs, it is advisable to cut off the old
flowers after the petals have fallen. The energy which would have
been used in seed production is then available for the production of
additional flower buds for the following season. Certain Apple varieties
often set so many fruits that few flowers are produced the next year.
Due to the few fruits produced the second year the tree is able to set
an unusually large number of flower buds and the third year there is
again an excess of fruit production. These varieties tend to bear only
in alternate years and the cycle is disturbed only when fruit develop-
ment is prevented by natural or artificial means.

In wind-pollinated plants the pollen grains are produced in enormous
numbers. They are light and dry enough so that they are carried long
distances by the wind. Some pollen grains have small, wing-like pro-
jections which also aid in their dispersal. It has been estimated that
a large American Elm may produce billions of pollen grains, but only
a very small percentage of these is carried to the stigmas and effect
fertilization. Some of the Pines produce so much pollen that the ground
may be yellow with pollen grains in sheltered areas.

In these wind-pollinated plants the flowers may be perfect and in-
clude both male and female organs, as in the Elms. In the Conifers,
the male and female cones are borne on the same tree. Some
of the Maples have the male and female flowers on different trees.
In such species it is essential that enormous numbers of pollen grains
should be produced to insure adequate fertilization and seed production.

1()

Most trees and shrubs with conspicuous flowers are insect pollinated.
In such species the pollen adheres to the opened anthers and is not car-
ried by the wind to any great extent. The Rhododendron pollen grains
are held together in groups of four and these “tetrads” are united by
very delicate sticky threads. The Apples, Pears and Cherries are almost
entirely dependent on insects for the transfer of pollen from one tree
to another, and since most of these fruit trees are self-sterile, fruit
production is dependent on the activity of bees during the blossoming
season.

Great variation is found in the length of time between pollination
and seed production in different species. Most Elms are pollinated
about the middle of April in this region and the seeds are mature early
in June. A relatively short period is necessary for seed development
in some of the Maples. In most of the trees and shrubs, such as the
Lilacs, Apples, Deutzias, and Roses, the seeds do not mature until
fall. Most species of Pines require two years for the female cones to
mature. Tne various stages in development are shown in the accom-
panying drawing of cones of Pinus pungens. The male cones (figure 1)
shed their pollen in the spring and some pollen grains lodge between
the scales of the female cone (figure 2). The female cone develops
but fertilization does not occur until the following spring. During the
second season the seeds develop and the female cone reaches maturity.

Karl Sax.

The display of flowering cherries is particularly fine this spring, and
while the collection at the Forest Hills Gate is already past its prime
the newer plantation on the Overlook is not yet in full bloom. The
Crabapples are just beginning to open and will be in full flower before
the Cherries have passed. In the Shrub Collection the Arboretum’s un-
usual and extensive collection of Japanese Quinces is beginning to bloom
and should be in fine condition for another week.

EXPLANATION OF PLATES

Acer saccharinuiti (Earliest flowering native tree). 1, Stam-
inate flowers; 2, Pistillate flowers; 3, A single staminate flow-
er; 4, A single pistillate flower; 5, A pistil; 6, Pistillate flow-
er, vertical section; 7, Leaves and fruit; 8, Base of fruit, ver-
tical section; 9, seed, vertical section; 10, embryo; 11, Embryo
showing cotyledons; 12, Branchlet in winter.

From drawing by C. E. Faxon for Sargent’s “Silva of North
America”.

Pinus pungens. 1, Male cones which produce the pollen; 2,
Young female cone; 3, One year old female cone at top. Mature
cone at base of branch. Two years are required from pollina-
tion to seed production in most Pines.

From drawing by C. E. Faxon for Sargent’s “Silva of North
America”.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI MAY 18, 1932 NO. 5

Cherries and Peaches. The early flowering Japanese and Chinese
Cherries never flowered more beautifully than they have this spring.
The past winter was so mild that practically every flower bud survived.
Flowers were borne on every branch from the ground up. The situa-
tion of the largest trees, near the Forest Hills Gate, is not always
favorable to such beautiful development, because the land in this lo-
cality is more or less basin-shaped and forms a pocket for the cold air
which has no free flow, hence in this locality the lower parts of the
trees are subjected to several degrees of lower temperature than the
upper parts, and the blossom buds near the ground are very likely to
be wholly or partly destroyed if the mercury falls to zero (Fahrenheit)
or below.

The semi-double and the double-flowered forms of the Japanese and
other true Cherries are usually distinctly later in blossoming than those
with normal, single blooms and as the latter fade away the former
come into their best condition. The flowers endure much longer than
those of the single forms, whose petals may begin to drop in forty-
eight hours after the flowers expand. Much depends, of course, upon
weather conditions.

The best collection of the later flowered Cherries in the Arboretum
is on Bussey Hill and is now well worth a visit. The better forms or
variations have so often been described in these bulletins that it seems
unnecessary to repeat names when these are plainly given upon the
plants for all who visit them. All forms do not bloom at once and
plants with beautiful flowers continue to be of interest through the
third week of May.

Peaches {PrunuH Feraica) were in full bloom about May 6th or 8th.
A number of the more popular kinds grown for their fruit show
marked differences in their flowers. Plants like the well known com-
mercial Peach, the Elberta, have much smaller and less showy blos-
soms than the flowers of Carman, an earlier ripening Peach, which is
widely and extensively cultivated for its fruit. This garden variety

17

18

has large, broad-spreading, pink petals; an orchard of this Peach in
bloom is well worth a long journey to see. The double-flowered forms
of the Peach are as interesting and beautiful as are the Japanese Cher-
ries. Three forms deserving particular mention are the Double White,
Double Pink and Double Red. Unfortunately, they appear to be even
shorter lived than the normal Peach tree and far less enduring than
the Cherries. They will be past flowering when this bulletin is issued.

Juneberries. Some of the earliest shrubby Juneberries or Shadbushes
( Arne lane hier) were in good blossom in the last week of April. Now,
May 8th, the Smooth Shadbush or Juneberry {Amelanchier laevis) is a
conspicuous feature in the natural landscape, being covered with its
fleecy white bloom that is accompanied by unfolding, reddish purple
leaves. As a small garden tree, with single trunk, it is much to be
preferred to the Gray-leaved or Swamp Shadbush or Juneberry {Amel-
anchier oblongt folia) , another natural feature in our landscape, but one
usually found in moist ground or on cool slopes. Amelanchier laevis
frequents drier situations than A. ohiongifolia , although both species
grow well in ordinary garden soil. The Gray-leaved Shadbush has the
young leaves heavily covered on the under side with a white tomentum
before they fully expand; this tomentum is also abundant on the ra-
cemes of flower buds. The smaller, duller white blossoms of A. ob-
longi folia are less attractive than those of A. laevis. As a small tree,
it usually has a narrow habit of growth and develops several upright
stems from the ground, some of them slender. Often the whole plant
assumes the habit of a large, round-topped shrub. Just now it is one
of the most common and conspicuous plants, forming a striking con-
trast with other vegetation against the brown hillsides and leafless
woodlands, and in the blueberry swamps.

Another native species with arborescent habit is the so-called Canad-
ian Shadbush or Juneberry {Amelanchier canadensis), which is distin-
guished from the other species referred to by having its young leaves
more or less tomentose on both sides, whereas, they are glabrous in
A. laevis, as already stated, and heavily tomentose on the under side
only in A. ohiongifolia. Its fruit is also described as tasteless, but in
the other two as sweet. This quality is variable, however, and can-
not, well be relied upon as a specific character. The Canadian June-
berry occurs with A. laevis over much of the same geographical range
as the latter, although it does not appear to extend so far north. A
most interesting natural hybrid between these two species has been
named Amelanchier grandiflora. It is a very floriferous little tree, the
flower buds on some individuals being tinged pink, the petals showing
some trace of the same color. This offers the suggestion that we may
yet have a pink or red flowered Juneberry in cultivation. Some of the
species of Amelanchier are mere shrubs and altogether they may de-
velop a sequence of blossoms lasting several weeks. It is unfortunate
that they do not have a generally accepted English name. Juneberry
and Shadbush appear to be most common in use, though they are also
known as Service-tree, this being the name adopted by the U. S. For-
est Service and some other American botanical authorities, though

Amelanchier canadensis

20

sometimes modified as Service-berry. “Standardized Plant Names”
uses Shadblow. In the confusion of local names a resort to Amelan-
chier, a Savoy name for the European species A. ovalis, offers a relief.
Linnaeus accepted the local name as a specific term in his nomen-
clature. Shadbush seems a misnomer w'hen applied to a small tree.
The name Service-berry is certainly less known in this country than
Juneberry, so named from the fact that the earliest fruits mature in
that month. The prefix “Shad” to names of some of our eastern
species refers to the coincidence of bloom with the annual movements
of shad fish in our streams. Species of the genus occur from the At-
lantic coast to the Pacific, and from Newfoundland and the Hudson Bay,
and near the Arctic Circle, to the mountains of Mexico. The genus
also occurs in Asia as well as in Europe, the best known Asiatic species
in cultivation being AmeAanchier asiatica. This is inclined to be ar-
borescent. In the Arboretum it is one of the latest of the Amelanchiers
to blossom.

All of the Juneberries or Shadbushes bear edible and often quite
palatable fruits. Not much has been done to improve these by arti-
ficial processes, but selections of the best found growing wild have been
made. The edible qualities of these fruits in the wild state have been
of great advantage at times to explorers and pioneers who relished them
when other fresh fruit supplies were scarce. The North American
Indians over a wide range of our country appreciate the fruit either in
a fresh or dried state. When properly dried the fruits have something
of the quality of raisins.

Visitors to the Arboretum are advised that on Bussey Hill the beauti-
ful pink-flowered Rhododendron Schlippenbachii is passing its best con-
dition and the Poukhan Azalea is a mass of lilac-purple color. Kaemp-
fer’s Azalea from Japan may be seen in fine condition in the same
locality. Viburnum Carlesii is in flower in the group near the Centre
Street Gate; many Crabapples are already in flower and others are rap-
idly following, the best collection being on the north and east sides of
Peters Hill.

The cool weather has held back the flower show of some popular
plants. Among these are the Lilacs, which at the present time. May
10th. do not appear as though they would be in best condition until
about May 22nd, although a very early and interesting hybrid, Syrivga
hyacinthijiora, opened its first individual little flowers in the first
week of this month. J. G. Jack.

EXPLANATION OF PLATE

Amelanchier canadensis (Juneberry). 1, flowering branch,
reduced; 2, diagram of flower; 3, vertical section of flower,
petals cut, enlarged; 4, stamens, enlarged; 5, cross section of
ovary, enlarged; 6, ovule, magnified; 7, fruiting branch, reduced;
8, fruit, vertical section, enlarged; 9, fruit, vertical section,
enlarged; 10, seed, enlarged; 11, embryo, magnified; 12, winter
buds, reduced.

From drawings by C. E. Faxon for Sargent’s “Silva of North
America”.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI

JUNE 4. 1932

NO. 6

Fire! In the early afternoon of April 30th fire broke out at the
base of Hemlock Hill. Fanned by a stiff wind, it ran up the south-
east face of the hill, ruining a fine plantation of Japanese Yews and
leaving an ugly scar on the hillside before it was finally subdued. Dur-
ing the last few years the thrifty grove of young Hemlocks at the
base of the cliff has been a lovely sight the year round. It will take
skillful replanting and ten years of care before this part of the Ar-
boretum can be restored to its former beauty. The fire was fortunate-
ly far enough around the base of the hill so that the damage is not
visible from the South Street Entrance.

Disheartening as is such a fire to those who are interested in pre-
serving and developing the beauty of the Arboretum, the complete
record for the year is far more alarming. While the fire of April 30th
was somewhat more spectacular than the average, it was only one of
ten major fires this spring. All of these caused some damage, yet all
were avoidable and some of them were deliberately set. In spite of the
vigilance of the Superintendent, in spite of a special fire guard and
patrol track with fire-fighting apparatus, there have been over twenty-
five fires in the Arboretum in the last six months. A partial record
for this period is as follows:

Fall of 1931. South Street Nursery. Small fire built in the nursery
by boys playing about the pond. Killed several Willows.

Oak Woods. Leaf fire in the Oak woods back of the Dawson house.
Large area burned over but little actual damage to important specimens.
This fire was deliberately set by four boys who were seen but escaped
in the confusion.

Bussey Meadow. Several fires, one of which was set, and one of
which spread from a brush fire on adjoining property. Relatively little
damage.

22

Peters Hill. Grass fire. Several trees badly scorched.

Hussey Dormitory. Grass fire near the public footpath. Apparently
started by a careless smoker.

Spring of 1932. Corner of Hussey and South Streets, April 12. Killed
the lower branches of several Hemlocks. Of unknown origin.

Walter Street Meadow. Grass fire started by boys. Damaged sev-
eral young Larches.

Oak Woods and Pinetum, April 18. Pour fires deliberately set by a
gang of boys, who threw matches and leaves into the grass as they
walked through. They were seen by two students but escaped. One
of the fires damaged the collection of young Chinese Pines.

Hemlock Hill, April 30. The fire described above.

Bussey Dormitory, March and April. Three fires in the shrubbery
along the Arboretum border. One apparently started accidently by
smokers. The other two, which occurred on the same day, had every
appearance of being deliberately set. A fine southern Yellow-wood was
ruined and the fire had ignited the house before the firemen arrived.

Oak Woods, May 21. Two small fires, apparently set. Little damage.
One grass fire near the railroad on the same day.

Vandalism in the Arboretum has reached a point where friends of
the institution need to know the damage that is being done and the
danger to which we are exposed. Only a very few of those who come
here for recreation misuse that privilege, but these few cause damage
which is mounting into the tens of thousands of dollars. These hood-
lums hold midnight carousals on Hemlock Hill, littering the ground
with broken glass. They deliberately twist off the metal labels from
trees and shrubs, so that valuable information is sometimes lost for-
ever and the yearly replacement bill is terrific. They break hundreds
of unopened flower buds off the Rhododendrons in the early spring.
They throw stones through the windows of the Administration Building
for the pure joy of breaking glass. Fire is, at present, their most
dangerous ally. A single fire, backed by a strong wind could ruin
Hemlock Hill. It has taken nature at least a thousand years to produce
this outdoor cathedral. One hoodlum, one irresponsible youth, who
likes to see the fire engines, may some day destroy it in half an hour.

So much for the problem. What can be done about it? The Arbor-
etum is doing its best by both direct and indirect methods to save the
Arboretum from a small percentage of the public for the public at
large. Two hundred and sixty acres are not readily guarded, either by
city police or hired watchmen. During “fire weather” a truck equip-
ped with fire-fighting apparatus is on constant duty. Four members
of the staff have homes in or near the Arboretum and these homes
serve as watch towers in preventing vandalism and in reporting fires in

Before and After: Two views of Hemlock Hill demonstrating the
effect of the recent fire.

24

their early stages. In the last year the busy housewives in these four
homes have turned in the alarms for at least half of the fires in the
Arboretum.

It may eventually be possible to develop a system of Sunday and
holiday patrol in cooperation with the Boy Scouts. A promising start
in that direction has been made this spring. A knowledge of what the
Arboretum is and what kind of work it is doing, diffused through the
immediate neighborhood, may eventually prove a deterrent force.

One weapon which can be used against hoodlumism is public opinion
and it is for that reason that a whole number of the Bulletin has been
devoted to the subject. The Arboretum is located in Jamaica Plain
but it is known throughout the world. It belongs to Boston and to the
country at large. It serves the public everywhere. It must not be
kept at the mercy of a few irresponsible youths.

Edgar Anderson.

Plants of Current Interest. With the first week of June, spring
has suddenly given way to summer in the Arboretum. The Cherries
and the Crabapples are gone, the Lilacs are rapidly going, but the
Phododendrons and the late Azaleas are here to take their places. One
of the most unusual trees in flower at the moment is the “Empress
Tree” (Pauloivnia tomentosa), of which a splendid specimen can be seen
near the Centre Street Gate. Originally from China, it has long been
in cultivation in the Orient and was long ago introduced into southern
gardens. It has made itself very much at home in the southern states
and has run wild to such an extent that it might easily be taken for
a native American tree. Its showy violet-colored flowers are seldom
seen in Boston, for the tree is not quite hardy here and is at its best
only after a succession of mild winters.

The display of named varieties of the common lilac is rapidly pass"
ing by, but many of the later-flowered species are just opening their
flowers and will be in fine condition for at least another week. In the
Legume collection below the Lilacs the Rose Acacias, Laburnums,
and Black Locusts are in splendid condition. The flow’ers of all three
are essentially similar in shape but those of the Black Locust are pure
white, those of the Laburnums are brilliant yellow, and those of the
Rose Acacias are soft pink.

Visitors with limited time at their disposal are advised to spend most
of it in the neighborhood of the South Street Entrance. On the slopes
of Bussey Hill are to be found Azaleas in a rainbow planting of pink,
yellow, white, orange, purple, and scarlet. At the foot of Hemlock Hill
the Rhododendron collection is already full of color. Under the hem-
locks and among the red cedars the ferns are rapidly unfolding and
their light green fronds contrast handsomely with the darker shades
of the conifers.

EXPLANATION OF THE PLATE
Two views of the eastern slope of Hemlock Hill. Above:
The undamaged northeast face. Below: A portion of the fire-
scarred area.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI JUNE 9. 1932 NO. 7

Hawthorns. In the fourth volume of Charles Sprague Sargent’s “Silva
of North America”, published in 1892, there appears an enumeration of
the native species of the genus Crataegus. The generic name Cratae-
gus is derived from the Greek word kratos, referring to the hardness
and strength of the wood. Commonly the group is known as Hawthorn
and is sometimes called Thorn Apple, or Haw. The term Hawthorn
appears to be derived from the old form hage or haeg, a hedge, and
thorn in allusion to the sharp pointed spines usually characteristic of
the genus. “May” has been used very often in English literature for
the so-called English Hawthorn. Sargent states that about forty spe-
cies of Crataegus are known, these being about equally divided between
the Old World and the New, fourteen species being natives of the United
States. In 1902, ten years later, in a supplementary volume (Vol. XIII)
Sargent included eighty-four species as coming within the region
covered by the Silva, but in his enumeration he did not admit a num-
ber of species that are recognized as shrubs rather than trees. At this
time he stated that the number of American species was vastly great-
er than had been previously thought to be the case and that for their
recognition and description some later work on American dendrology
would have to be prepared.

The Hawthorns comprise a group of trees and shrubs which normally
have white flowers and pomaceous or apple-like fruits. The fruits are
usually red but may be yellow, purple, black or green when ripe. Al-
though they resemble small crabapples they exhibit a marked botanical
difference in the hard bony coverings of the seeds. The petals are five
in number except when there is a tendency for the flowers to become
double. The stamens are usually five, ten, fifteen or twenty or some-
times twenty-five in number and, with the color of the anthers, are re-
garded as of specific value in separating closely related species.

Horticulturally and in general garden practice, the Hawthorns may
be expected to thrive under the same conditions as apple trees. They
have not received the attention they merit as small ornamental fiower-

25

26

ing trees, or as hedge-plants or for their fruits which are often showy
and of value as food for birds and sometimes also for man.

The so-called English Hawthorns of our gardens are usually classed
under the botanical name of Crataegus Oxyacantha but there is another
species, Crataegus monogyna, which closely resembles it ana is often
confused with it. The fact that they have hybridized adds to the con-
fusion. Besides some differences in the leaves, the two species are
differentiated by C. Oxyacantha having usually two of the hard bony
nutlets or seeds in the fruit while there is only one in C. monogyna.
The latter becomes a larger tree, attaining a height of over thirty feet.
These w’hite flow’ered trees are still occasionlly seen in our gardens tut
they are considered less desirable than some of the garden forms
which have been derived from the types. They apparently have
a greater tendency to produce colored flowers than has been shown by
any of our native American species, although by long cultivation and
selection we may develop from these many interesting garden forms.
Of the European forms in cultivation Crataegus Oxyacantha plena, or
multiplex, with very small rosette-like or double white blossoms, is one
of the best of its kind. Among those with colored flowers Paul’s
Double Scarlet takes first rank for its brilliant scarlet blooms. It is
the most conspicuous of the Thorns in brilliance of color. These var-
ious garden forms must be grafted or budded as the plants cannot be
growm from cuttings.

There are other foreign species of Crataegus found in our parks and
gardens but they are generally considered rare or uncommon. Among
them Crataegus pinnatifida, from northeastern Asia, is one of the most
interesting. This becomes a small tree twenty feet in height, with
large deeply or pinnately lobed, lustrous leaves, large flowers and large
dark red fruits. A horticultural form, C. pinnatifida major, from north-
ern China, is cultivated by the Chinese as an orchard tree for its edible
fruits which are sometimes an inch in diameter.

The collection of Hawthorns in the Arnold Arboretum is mainly lo-
cated on the slopes of Peters Hill and, so far as possible, the chief
groups have a frontage on the main driveway. With the possible ex-
ception of the collections in the parks of Rochester, New York, the
Arboretum contains the largest collection of American specits in cul-
tivation. Students may And plants of various species in flower during
a period of flve or six weeks.

The flrst species to show open flowers is Crataegus Arnoidiana . It
was originally found growing naturally on the grounds of the Arnold
Arboretum and although afterwards discovered in a few' other places
it appears rare in a natural state. It was named by Professor Sargent
for James Arnold who by his will gave the original fund w'hich made the
Arboretum possible. This season the flrst flow'ers w'ere found open on
May 12th, these being about three-quarters of an inch in diameter and
provided with ten stamens with yellow anthers. The trees become
twenty or twenty-flve feet in height, having stout trunks and broad
rounded tops. The fruits are bright crimson, sometimes nearly three-

t

Crataeffus Arnoldiana. 1, Howering branch; 2, section of flower;
3, calyx-lobe; 4, fruiting branch; 5, section of fruit; 6, nutlet.
All reduced.

From drawings by C. E. Faxon for Sargent’s “Silva of North
America’’.

28

quarters of an inch in diameter and mature about the middle of August,
usually falling before the first of September. They have a pleasant sub-
acid fiavor. The fruits of some species, as Crataegus submollis, bright
red or orange-red in color, are often gathered and made into preserves
or an excellent jelly, either pure or in combination with some other fruit,
such as crabapples.

In another group we have Crataegus cocci nio ides, a broad-spreading,
low, round-topped tree producing large flowers, about three-quarters of
an inch across, and globose dark crimson fruits with thick red flesh
which should make excellent preserves. Its foliage, which is tinged
red when unfolding, turns orange and scarlet in the autumn. The
Hawthorns already mentioned are less known to the general public
than the Cockspur Thorn {Crataegus crus-galli) which represents an in-
teresting series of species extending from the Province of Quebec, near
Montreal, southward to Florida. There is often confusion among nursery-
men with regard to the species as at present known and apparent and
unintentional substitution sometimes occurs. What is accepted as true
C. crus-galli is a species with late flowers, having ten stamens with
rose-colored or purple anthers; the leaves are lustrous, narrowly oblong-
obovate tapering to a cuneate short-stalked base, usually rounded at the
apex, sharply serrate and rarely lobed. The fruit is red and per-
sists late. The species may become a tree thirty or thirty-five feet
high but it is often low and broad-spreading. It is an interesting and
useful tree either grown singly or as a strong barrier hedge, for which
it is well adapted.

Some interesting supposed hybrids have been developed from this
species or its allies, but they are as yet little known in this country.
Among these may be mentioned Crataegus Lavallei having leaves which
turn bronzy-red late in autumn and fruits which remain on the trees
through the winter, and C. persistens which holds its foliage in a green
condition until early winter and with it bears its conspicuous and per-
sistant red fruit.

Crataegus punctata, the Dotted Thorn, is a representative of another
group which grows naturally in eastern North America from Canada to
Illinois and Georgia. While a low tree twenty or more feet in height
its branches may spread over an area forty or more feet in diameter.
It is well worth planting in parks or where there is plenty of room for
the development of its normal beauty. It is rather late in flowering but
blossoms before the Cockspur Thorn.

The latest of the Thorns to bloom is the Washington Thorn {Crataegus
phaenopyrum, or C. cordata), which becomes a small erect tree with
rounded top. It bears small flowers in many flowered corymbs, small
scarlet fruit which persists through the winter, if not earlier eaten by
birds, and handsome clean foliage which turns scarlet and orange in
the autumn.

The thorns mentioned are among those best known in general planting.
The collections in the Arboretum must be studied to get a fair idea of
the diversity and richness of our hawthorn flora.

J. G. Jack

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI JUNE 24, 1932 NOS. 8&9

Rosa rugosa and its Hybrids. No exotic rose has made itself more
at home in New England than the Asiatic species, Rosa rvgosa. From
the Bay of Fundy to Long Island Sound it is found growing sponta-
neously on sandy beaches quite as though it were a native American
species. First reported as running wild in 1905, it is now known from
the Elizabeth Islands, the Penikese Islands, Yarmouth, Nova Scotia,
and from many intermediate points. In some of these situations it
has merely “jumped over the fence” from a nearby garden. But in
many of them, as on the Gurnet at Plymouth, Mass., it is found mak-
ing itself thoroughly at home on isolated sand spits far from any garden.

Rosa ragosa is a rampant, thrifty grower and is most decidedly a
plant for the shrub border rather than for the formal rose garden. It
can be trusted to look after itself more than can most roses, for it is
winter hardy and resistant to such diseases as “black spot”. If the
bush becomes too large and scrawny it can be cut back ruthlessly
close to the ground and will respond with clean new growth. It is
particularly useful in situations where ordinary roses would be killed
in cold winters or in seaside gardens where its natural tolerance of salt
water gives it a special advantage.

The foliage is a shiny dark green and is held crisply erect. In the
typical form, the Howers are dark magenta, single, and very large,
sometimes reaching over five inches in diameter. There are varieties
which are semi-double as well as white-flowered and pink-flowered
varieties. The flowers are borne more or less throughout the summer
and are succeeded by brilliant fruits which gleam like large enamelled
beads among the dark green foliage. When the frost comes the leaves
also turn color and finish the season in glowing shades of orange and
scarlet.

Quite as interesting as the species itself are the numerous hybrids
which have been made between it and other kinds of roses. It has

29

30

been remarkably fertile in crosses, and hybrids with the following
species have been recorded: R. arvensis, K. chinensis, K. odorata, R.
borboniana, R. palustris, R. blanda, R. Carolina, R. Roxburghii, R. mvl-
tifiora, R. Wichuraiana. Even in the Arboretum’s modest collection
of hybrid roses there are over fifteen w’hich carry the blood of Rosa
rugosa. These hybrids are now in flower in the Shrub Collection.
Most of them are grouped together in one bed at the south edge of
the collection; a few will be found scattered among the other species
of roses. They are particularly interesting when considered as a group
and compared with their parent species. In all of them the influence
of R. rugosa is evident in their shiny, rugose leaves, large flowers,
and vigorous growth. Unfortunately, some of the undesirable charac-
teristics of R. rugosa seem to have been passed on quite as regularly,
for nearly all of the hybrids have weak flower stems and a somewhat
weedy habit of growth. All in all, however, they are a fine lot of
flowering shrubs and should be much better known. As the president
of the American Rose Society has said, “They are of yet unrealized
garden value’’.

It would seem as though many of these Rugosa hybrids might be
useful in producing new varieties of hardy roses. It should be pos-
sible in further crosses to keep the better Rugosa characteristics and
lose the less desirable ones. For the convenience of those amateurs
who are doing breeding work with roses, the pollen of the hybrids in
the Arboretum’s collection has been examined in the Cytological Lab-
oratory. In the following discussion the percentage of fertile pollen,
as determined by microscopical examination, is reported for each hy-
brid where buds were available for study.

Lady Duncan [R. rugosa X R. Wichuraiana).

Pollen fertility 20%.

A vigorous trailing rose, useful for holding banks, but not suitable
for growing on a trellis. Flowers very large, fragrant, single and a
vivid, clear pink. Foliage dark green, resistant to black spots. This
was one of the hybrids produced by the Arboretum’s first propagator,
the late Jackson Dawson.

Max Graf {R. rugosa X R. Wichuraiana) .

Pollen fertility 20%.

Very similiar to Lady Duncan, and therefore probably of the same
ancestry, although R. setigera has been reported as one of the parents.
The flower buds and foliage are slightly darker than those of Lady
Duncan and the plant is somewhat more vigorous. This hybrid was
raised at the Bowditch Nurseries in Pomfret Center, Connecticut, and
bears the name of a gardener who was with the firm for many years.
In the vicinity of Chicago, Max Graf has been used extensively as a

m A m

Rosa rugosa var. kamtschatica

32

bank cover in gardens along the Lake Michigan bluffs. In eastern
Missouri it has withstood successfully the cold winters and blazing sum-
mers of that trying climate.

New Century {R. rugosa X R. miiltijiora “Cl-OTlLDt: Soupert”).

Pollen fertility 107f'.

Flowers large, fragrant, flesh-pink and fully double. Foliage light
green. This variety and Sir Thomas Lipton were both originated by
the late Dr. Van Fleet of the U. S. Department of Agriculture, who
is known particularly for his hybrid climbing roses. Silver Moon and
American Pillar.

Sir Thomas Lipton {R. rugosa X R. multiflora “Clotilde Sou-
pert”).

Pollen fertility 20%.

Though this rose came from the same cross as did New Century,
it has much more the appearance of the next variety on the list,
Blanc Double de Coubert. Like that variety its flowers are white
and fragrant, sometimes showing a trace of pale pink in cloudy
weather. It is reported as being much more of a continuous bloomer
than the other large- flowered Rugosa hybrids. The foliage is dark
green and glossy, the bush large and vigorous. Its general effect in
the landscape is very fine.

Blanc Double de Coubert {R. rugosa X R. odorata).

Pollen fertility 35^o.

This variety was originated by Cochet-Cochet and has been various-
ly reported as a sport of R. rugosa alba, and as the result of a cross
with another species. The low pollen fertility would favor the latter
interpretation. As compared to Sir Thomas Lipton the foliage is
darker green, the bush less shapely and the flowers larger.

Alice Aldrich.

Pollen fertility 50^o.

From the appearance of this rose one might suspect it to be the
result of crossing the old-fashioned pink Moss Rose with R. rugosa.
The flowers are borne in clusters, the buds are pointed and open into
fully double bright pink flowers. The foliage is thin for a Rugosa
hybrid, the bush is thorny and of a rather floppy habit.

Arnoldiana [R. rugosa X R. horhouiana “General Jacqueminot”).

Pollen nearly all sterile.

33

This was another of the hybrids produced by Jackson Dawson. The
flowers are single and a brilliant shade of dark crimson. The bush is
a very vigorous grower.

Agnes {R. rugosa X R. foetida ^'Persian Yellow”).

Pollen nearly all sterile, but apparently a few fertile grains.

This lovely rose, only recently becoming well known in the United
States, was produced in 1900 by the Canadian plant breeder, William
Saunders, who was then Director of the famous Experimental Farm at
Ottawa. The flowers are a soft primrose yellow and semi-double.
They are delightfully fragrant, the odor being a blend of the heavy
rugosa perfume and the almost medicinal scent of the Persian Yellow.
While very distinctive, it is quite similar to the delicate fragrance of
most Tea Roses. The foliage is similar to that of R. rugosa. The variety
is not only desirable for its beauty but for its extreme hardiness. It
has been reported as having come unscathed through winters which
killed other Rugosa hybrids back to the ground. In 1926 it was
awarded the Van Fleet Gold Medal by the American Rose Society as
being the most distinctive new rose originated in America.

F, J. Grootendorst {R. rugosa X R. multijiora “Mme. Norbert
Levavasseur”).

Pollen less than lO^o fertile.

A hardy, everblooming rose. The flowers are small, very double,
and with notched petals, giving the effect of a small red carnation.
They are fragrant and are borne in clusters all through the summer.
The foliage is dark green, rugose, and leathery.

R. rugosa X R. ferruginea.

Pollen fertility 60^,

Flowers white and single, borne in clusters. Foliage thin but tough.
The general effect is that of a tall, white-flowered wild rose.

Ruskin {R. rugosa X “Victor Hugo”).

Pollen practically all sterile.

Ruskin is another of Dr. Van Fleet’s hybrids. It has fully double
flowers of bright, dark crimson borne singly or in small clusters. It
is very fragrant and has leathery dark green foliage.

34

Belle Poitevine.

Pollen fertility 90 ^/c.

The flowers are large and semi-double, very similar to those of R.
rugoaa in appearance and verging too closely on magenta to be general-
ly popular. The variety is very hardy, however, and is a reliable
bloomer.

Nova Zembla.

Pollen fertility 20^/c.

This variety and the very similar Conrad Ferdinand Meyer are
vigorous hybrids with fully double flowers resembling those of a
hybrid tea or hybrid perpetual. It has long-pointed buds, borne
several in a cluster on stout stems and opening into a fragrant flower
of pale shell pink. It is almost too vigorous and requires severe
pruning out of old canes to be kept within bounds. It is sometimes
planted as a hedge around rose gardens to form a background for the
lower growing varieties.

Schweidnitzia.

Pollen fertility 109'c.

The flowers are white and semi-double. The bush is low, the foliage
dark green and leathery.

These few hybrids of Rosa rugosa are a motley group. Some are
high shrubs, some low bushes, and some are vines. Their flowers are
white, red, pink, and yellow; small and large; clustered and single.
All of them are only partially fertile; none of them, so far as we
know, are absolutely sterile. Various as they are, their variety is as
nothing compared to the hidden possibilities locked away in their pollen
grains and egg cells. Any one of these hybrids would give rise to
varied progeny. It is beyond the limits of the human imagination to
conceive of all the possibilities which might result from inter-crossing
these fifteen varieties. Yet out of the thousands of hybrids which
could be raised only a few would be worth growing. How then to
select these few? Though the laws of heredity are in the process of
being revealed, we still know relatively little about what happens
when species are hybridized. We can usually explain the results we
get, but we cannot predict the possibilities. It is for this reason,
among others, that much of the time of the Cytological Laboratory of
the Arboretum is spent on problems which have no immediate bear-
ing on plant breeding but which do add to our knowledge of how
hybrids behave. When a little more is known about hybrids between

35

species, it will be possible to recommend in advance the particular
crosses, out of the hundreds which might be tried, which will yield
the desired results. When this time comes we shall, indeed, be able to
produce the rose visioned by Mr. Wilson, “The hardy rose of the
future — the rose for the cotter’s porch, for the rich man’s garden; the
rose that needs no protection in winter, the rose that will thrive in the
coldest parts of these United States of America’’.

Edgar Anderson.
W. H. Judd.

Plants of Current Interest. The finest display in the Arboretum is
still along the valley of the Bussey Brook and at the foot of Hemlock
Hill. Though the Rhododendrons are rapidly dropping their brilliant
trumpets, the Mountain Laurel is quite as rapidly coming into flower
and while not so gorgeous in its coloring it is even lovelier in its gen-
eral effect in the landscape. Further up the valley the conifers, with
their clean new foliage are now as beautiful as if they were in flower.
The blue spruces and silver firs are their very bluest and the Nikko
Fir {Abies homolepis) is a symphony of contrasting greens; the old fol-
iage is a dark bluish green, the new foliage much lighter, and the bloom
on the backs of the needles a soft gray blue. At the very head of the
valley close to the Walter Street Gate, the Japanese Golden Larch
(Pseiidotarix amahUis) is in full leaf. Its soft green needles, borne in
whorls, are exquisite in their form and arrangement and well repay a
close examination. The young cones, on the higher branches, are
already large enough to be attractive. They are quite unlike the cones
of other conifers in their general effect and look rather like clusters
of pale green roses set along the upper side of the branches. They
will continue to be a lovely sight all through the summer and early fall
and will drop to pieces, scale by scale, just as the tree loses its needles
for the winter.

In the Shrub Collection and along the road through the lilacs, the
Mock-Oranges are about at their best. Every year the Arboretum
receives numerous inquiries by mail and telephone as to the proper
use of the words. Lilac, Syringa, and Mock-Orange. The name Syringa
is a somewhat unfortunate one, since it is used for two different
groups of flowering shrubs. As a common name it refers to the Mock-
Oranges, shrubs with large, fragrant, white flowers with waxy petals.
Scientifically these are classified in the genus Philadelphus. Syringa
as a scientific name belongs to the genus which includes the Lilacs and
Tree Lilacs, earlier-flowering shrubs with much smaller flowers borne in
large panicles. In using common names it is therefore better to refer
to the latter group as Lilacs and to the first as Mock-Oranges, and
avoid possible confusion.

86

One of the Arboretum’s most interesting exhibits is not really in the
Arboretum at all, but adjacent to it. For some years Mr. W. H. Judd
has been assembling a collection of hardy climbing roses in the nurs-
ery. These have recently been planted along the fence of the Bussey
Institution on South Street. While they have not yet reached their
finest development they are already showing up well. Many of them
will be in their best flower during the coming week, and since several
of the varieties are recent introductions, rose enthusiasts will find them
worthy of study. It has not yet been possible to label the collection
with conspicuous tags, but in nearly every case a small embossed metal
tag will be found on the fence close to each vine and bearing the
pertinent data.

EXPLANATION OF PLATE
Rosa rugosa var. kamtschatica.

From drawing in T. Nakai’s “Flora Sylvatica Koreana’’.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI AUGUST 13, 1932 NOS. 10 & 11

Botanizing from an Airplane. More than one householder in east-
ern Massachusetts was puzzled, one morning last May, by the peculiar
antics of an airplane which flew along the coast. Until it appeared
over the town of Ipswich, it behaved as might any other plane on a
pleasant spring morning. Once over that town, however, it began a
series of maneuvers which were as unusual as they were incomprehen-
sible. It darted back and forth from the town to the coast; it circled
over islands in salt marshes; it came swooping down over sandy beach-
es. With its motor shut off, it idled lazily at 2000 feet and then flew
directly to Newburyport, where it again flew this way and that way,
like a happy butterfly.

In spite of appearances there was a sober purpose behind these man-
euvers, which were repeated with minor variations all the way along
the coast from Newburyport to Duxbury. The airplane, or rather its
occupants, were actually botanizing. They were hunting for plants, or
to be more specific, for a particular plant, the Beach Plum, {Prunvs
maritima.)

It is far easier, in the confines of a short article, to describe an air-
plane search for Beach Plums than it is to explain ivhy any botanist
should want more data on the distribution of so common a plant or
should feel justified in gathering these data by plane. There were such
reasons, however. Anyone who knows only the most elementary facts
about plants knows that they are grouped in species; but just what
these species are, or how a species is to be defined, are questions that
not even the wisest botanists can answer. So at the Arboretum,
among other matters, we are studying a few species in great detail,
in an attempt to make as complete a record as possible of the varia-
tion within an entire species. We hope to find out, for instance,
whether a species is more variable at the center of its distribution or
at the periphery; whether unusual forms are found with greater fre-
quency in one part of its range than in another.

37

38

One might have supposed that such simple and fundamental informa-
tion would have been gathered long ago, but as a matter of fact, it has
never been done. For several reasons, our common Beach Plum, {Pra-
71U8 maritima), was selected for this kind of intensive study.- The
first question to be answered was, “What is its exact range; what are
its southern limits and its northern limits; where are the scattered lo-
calities at which it grows spontaneously away from the seashore?”
The second question was, “How much does it vary? What are the
ordinary limits of some easily measured character such as seed length
and width?” To answer this last question it was necessary to locale
large colonies of plum bushes, places like the Province lands at the
tip of Cape Cod where thousands of bushes grow side by side in great
profusion.

A first attempt to gather this kind of information had been made
last fall during the time when the plums were ripe. Over a week had been
spent in exploring the country along the south shore by automobile
and on foot. A few bushes were found in one place, a few more in
another, but away from Cape Cod itself, no really large colonies were
located. It was evident that any attempt to locate the best places
for study, even with the help of local botanists, would consume an
appalling amount of time.

At this point the junior author was consulted. Might it not be pos-
sible to map the distribution of the plums from the air and to find,
in a very short time, the largest colonies in the region? His talk of
“An hour’s flight to Portsmouth and back” was reassuring as far as the
time element was concerned. It remained to be seen if the Plums could
be identified practically at a height which would be safe for general
cruising, say 1000 to 2000 feet. A trial flight in the early spring showed
that it might indeed be possible to study the distribution of Beach
Plums from the air, particularly if the flights were made during the
season when the bushes were in full bloom. Every successive hour in the
air has justified this conclusion. It has been a matter of increasing sur-
prise to find how many trees and shrubs can be recognized, with a
little practice, at elevations of 1000 to 2000 feet. It might, in ad-
vance, have been suspected that species with conspicious flowers, like
the Lilacs, for instance, could be readily told at that height, but even
in the case of the Torch Azalea, it was something of a shock, as we
flew over the Arboretum, to find them even more conspicuous at 1500
feet than they are from the ground. With the morning sun shining
full upon them, they gleamed like a crumpled mass of orange-yellow
silk.

With a little practice, many genera of trees can be recognized, and,
in some cases, the species can be distinguished from heights so great
that no single detail of leaf or flower is seen. At second thought this
is not so surprising, as may be made clear from a comparison which
is much more than a mere analogy. Seen under the microscope, leaves
and flowers are found to be made up of myriads of cells. In the last
analysis it is the form and arrangement of these cells which determine

THE ARNOLD ARBORETUM
As seen from an Airplane

40

the appearance of the leaf or flower. If the cells are regular in size
and evenly spaced, the surface of the plant looks smooth and finished;
if they are irregular, the surface is rough. If the cells have thickened
walls, though our eyes may not see the walls, much less the thicken-
ing, they detect the hard, varnished appearance which results there-
from. In the same way the texture of a tree at 1500 feet is distinc-
tive, though at that height the individual leaves are invisible. It may
be even more conspicuous than it would be on the ground. Many fac-
tors contributed to this texture, the size of the leaves, how they are
spaced on the tv/igs, the character of their surface, the nature of the
branching, the angle at which the leaves are held.

So it is that at 1500 feet a Norway Maple in bloom can be recog-
nized by its glistening yellow-green color, like pale green bronze
covered with a light film of oil. The Shadbush (Amelanchier) blossoms
at the same time as the Beach Plum and often grows in the same
general locality, but they can be readily distinguished. On the Shad-
bush, the young leaves are scattered here and there among the flowers,
and they impart to the plant as a whole, a soft, almost woolly texture.
Sometimes the appearance of a plant from the air is so unexpected
that one must use a good deal of imagination to determine its identity.
The most puzzling species which we noted on our flight to Newbury-
port was a common feature in hilly pastures to the north of Boston.
Its color was a dark yellowish green, and in texture it was hard and
stiff. It looked, for all the world, like the circular patches of hard,
crusty lichens one often sees on rocks. What could it be? It was evi-
dently one of our commonest shrubs, since it occurred in pasture after
pasture, sometimes alone, sometimes intermingled with a tangle of other
vegetation. Before the puzzle had been solved, the coast was reached
and it was time to look for Beach Plums. It was not until we were
back on the ground that we realized that the lichen-like patches were
nothing more or less than the common Sweet Fern, {Myrica aspleni-
folia).

As for the Beach Plums themselves, they proved somewhat of a sur-
prise. It had been anticipated that, with such conspicuous blossoms,
they would, from the air, appear like glistening mounds of white. In
the first place they did not seem mound-like at all. I’hey are so low
that from an elevation of a thousand feet they look almost like flat
doilies upon the ground. While a single bush may be found covered
with flowers, it is much more characteristic for part of the branches
to bloom and part to be bare. Seen from a height, this irregularity
of blossom imparts a patchy appearance to the bush as a whole. The
black, bare branches and the flowering twigs blend together so that the
color becomes a grayish pink, rather than a pure white. The soft tex-
ture of the blossoms is dominated by the rough bark and spiny twigs
so that the bush, as a whole, takes on the hard surface of a pen and
ink drawing on very rough paper.

42

All these points were noted as we cruised back and forth above plants
at Ipswich, which had previously been studied from the ground. Then
we turned north to Newburyport and proceeded with our two objec-
tives for that morning. These were first, to map the coastal distribu-
tion of the species from Newburyport to Plymouth, and second, to
locate large colonies for study, somewhere along the south shore. We
had provided ourselves with geological maps covering the area in
question. They were mounted and folded and arranged in two bundles,
one for the north shore and one for the south. The south shore set of
maps was tucked safely out of harm’s way. The north shore maps were
numbered and ready. It was fast work for two people. The colonies
of plums had, first of all, to be discovered, then identified with certainty,
then their position and approximate extent indicated with red pencil
on the survey maps. The pilot ran the ship, keeping an eye out for
colonies far to the left or right and doubling back when the identity
of a plant was in doubt. The observer sat behind him in the cabin of
the ship, his lap a litter of maps, his coat pocket filled with a half dozen
red pencils. The map in use at the moment was spread out on his
knees, and the pencil was held above the last recorded locality. When
the plums were sighted, a few glances back and forth from the small
map to actual coast line itself served to locate their position. Then
a few quick strokes of the red pencil and back to the window again,
looking for the next colony of plums. Things worked smoothly until
we flew off the map. Then one had to work quickly to get out the
next map, open it, locate the plane’s position and start in charting the
plum distribution where it had been left off on the previous sheet.
One had to concentrate on the work in hand. There was no time for
sight-seeing and least of all for any attempt to snythesize the view
from the plane with one’s previous knowledge of the country below.

Viewed from an airplane, even the most familiar spot looks utterly
different from what it does on the ground, and one must use a great
deal of imagination to reconcile the two aspects. Hills disappear, trees
veil familiar buildings, the field of view is bewilderingly wide. For-
tunately a few features of the landscape are even more conspicuous
than they are from the ground, — roads, railroads, lakes, and islands.
By means of these landmarks it was comparatively simple to compare
the map and the view from the plane; they were substantially alike.
But any attempt to think of what was being seen from the plane in
terms of what had been noted on the ground, took too much time away
from the business in hand.

Occasionally there would be some question about the identity of a partic-
ular bush or clump of bushes. Then the pilot obligingly turned the plane
on its side and circled slowly above the spot, a maneuver which at first
defeated its own purpose. When the plane is on its side, the occupants
are also on their sides, a position at which one’s instincts rebel. This
proved the hardest single lesson for the observer to learn, the most
difficult bit of technique for him to acquire: that when the plane
turned over, instead of leaning back, he should do just the opposite

43

and welcome the opportunity for a free and unobstructed view straight
below. It takes some practice and not a little nerve to lean forward,
face against the window, and look calmly down for 1500 feet while the
plane does a gentle spiral on its side.

From Newburyport, after a short glance to the northward, we flew
south along the sandy coast, charting the distribution of Prunus mar-
tima in the towns of Ipswich and Essex. And there the Plums stopped.
Though the sandy stretches of Coffin’s Beach did not seem to differ
essentially from those of Plum Island, there were practically no plum
bushes on the beach or among the sand hills behind it. The few which
did appear were grouped at the north end, just across the Essex River
from Castle Neck, where plums were fairly plentiful. Nor did the
species reappear in quantity until Boston Harbor had been crossed.
We saw no bushes in Nantasket, but just at the town line of Cohasset
they reappeared and were soon one of the commonest bushes along the
coast. What causes this transition, in both cases so abrupt? We do
not know as yet. It may be due to some element in the soil; it may
be connected, in some way, with the recent geological history of the
coastal beaches; it may be due to some other quite unexpected cause.

By the time we reached the south shore, practice had made identi-
fication and recording of the plants an easy matter. There now re-
mained our second objective, the location of at least one large colony
where the variation of the species might profitably be studied. We
had not long to wait. Within a quarter of a mile of one of the localities
visited the autumn before, there was a large area of shifting sand.
It had been hidden from the road by the slope of the land and by a
thick growth of scrub-oak, but from the air it was most conspicuous.
It was so thickly studded with plum bushes that we did not even need
to fly directly overhead.

In company with a local naturalist, this colony was revisited the next
day, by automobile, to obtain pollen for microscopical examination. As
the car drove past nearly a solid mile of plum bushes the naturalist
exclaimed, “Why there are more beach plums here than I have ever
seen growing together in one place!” Though he had spent most of
his life only a few miles away and knew the countryside pretty thor-
oughly, fifteen minutes in the air had given us a more complete
knowledge of it than he possessed. In Duxbury we found another
large colony from the plane. Again it was only a short distance from
territory travelled through by automobile the year before. At fruit-
ing time this fall, these two colonies will provide abundant material
for study and experiment.

The speed with which the ground can be surveyed, particularly along
the coast, where there are ordinarily serious barriers to straight-line
travel, is nothing short of amazing to a novice in the air. When we
finally finished our charting of the plums along the south shore and
had returned to the landing field, we had been in the air one hour and

44

fifty minutes. In that time, we had explored the coast thoroughly.
We had flown over many islands, we had looked into the hollows among
the sand hills, we had examined the areas of higher land which rise
here and there among the salt marshes. It would have taken two weeks
by automobile and by foot and by boat to have covered the same ter-
ritory as thoroughy from the ground.

Best of all, we had ventured out into a new field and made a go of
it. We had tried out a new and unknown technique and had found it
even more useful than we had dared to hope. Here and there a few
botanists have used airplanes in their work, chiefly in the West, when
mapping the distribution of different types of vegetation. We had
gone even farther and had studied a particular plant from the air.
In the not far distant future such uses of planes in exploration and
study must certainly become not unusual. Some regions of the
earth’s surface seem particularly designed for exploration and study
from the air. Most of the sub-arctic zone, for instance, is dotted with
little lakes, which would solve the difficult problem of where to land
in the wilderness. It will not be long before these areas, now relatively
unknown, botanically, will be explored by plane. For the present there
is a certain satisfaction to us in having been among the first “air-
minded” botanists.

Edgar Anderson.
Oliver Ames.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL VI NOVEMBER 5, 1932 NOS. 12 & 13

Growing Oranges in Boston

Since 1929 the Curator of the Herbarium has been growing oranges
out of-doors at his home in Jamaica Plain, though, unfortunately for
him, the oranges in question are quite inedible. They are specimens
of the hardy Trifoliate Orange, Poncirus trifoliata (Citrus trifoliata),
a shrub or small tree native to China and commonly grown there and
in Japan. It was introduced into western gardens in 185C and has been
extensively planted in the southern states where it is used as an
ornamental shrub and as a hedge plant; it has escaped from cultivation
and has become naturalized in several localities. Along the Gulf Coast
in late years it has become something of a pest since it harbors the
undesirable citrus canker.

Specimen plants of Poncirus trifoliata are occasionally seen growing
without protection as far north as New York City but to the best of
our knowledge Mr. Rehder’s little orange tree is the only one to have
fruited regularly out-of-doors in Boston. Several attempts to grow
the species at the Arboretum have been unsuccessful, though at present
there is a small specimen in the nursery. Mr. Rehder’s Poncirus is
planted in a corner by the north wall of his home and in that way is
sheltered during very cold winter weather and is prevented from rushing
into growth during deceptive warm spells in the early spring.

As its name would suggest, the Trifoliate Orange is characterized by
compound leaves, each of which is made up of three small leaflets.
Almost as conspicuous as the leaves are the stout spines, one of which
is set directly above each leaf. The twigs are irregularly flattened and,
like the spines, are a bright, shining green, looking almost as if
they had been enameled. They interlace in all directions and with
their long thorns produce a barrier more impenetrable than a barbed-
wire entanglement. The flowers are similar to true orange blossoms
but are a little smaller, and with narrower, less conspicuous petals.
The fruits, here in Boston, ripen in the early fall and are of an attrac-

45

46

live bright golden color, particularly when seen against the clear green
of the leaves and young branches. Though orange-like in general
appearance, they are much smaller, being about the size of a large
walnut. When green they are covered with a soft down, which becomes
less perceptible as the fruit ripens. They are very aromatic and a few’
of them will scent up a whole room. To many people the odor is quite
plei-sant, suggesting Eau de Cologne; others find it rank and disagree-
able.

The exterior of the ripe fruit is so attractive that one is bound to
be disapp )inted on opening it. There is little to recommend the con-
tents. The seeds are large; they are even larger than those of the
cultivated orange, and they leave little room for the pulp, which is sour
and unpalatable. The rind is strongly impregnated with a bitter oil.
which inevitably becomes mixed with the juice as the fruit is opened
and gives it a vile flavor.

For over forty years experts in the Department of Agriculture have
been attempting to use the Trifoliate Orange in building up a new race
of semi-hardy citrus fruits. They have been successful to a surprising
degree in combining its hardiness with a more attractive flavor. They
have definitely succeeded in bringing the culture of citrus fruits out
of the tropics and into the edge of the temperate zone, but there is
as yet no indication that they w’ill ever make orange-growing profitable
in Boston.

The first hybrids were between Poncirus tn'foiiata and varieties of
the cultivated orange. They were called “Citranges” and while they
received a good deal of publicity when they were first introduced they
may be said to have been more encouraging than useful. The fruit,
though beautiful to look at, was scarcely larger than that of the Tri-
foliate Orange, and while the juice, taken by itself, could be used as a
substitute for lemons, there was even in the hybrid so much musky
oil in the rind, that special precautions had to be taken in opening the
fruit. Another bad trait of the hybrid was its too quick response to
warm weather in the early spring. It was, therefore, crossed with two
other citrus fruits, which, though not so hardy in other ways, were
slower to start into growth in the spring. These were the Kumquat,
Fortunella japonica, and the Calamondin, Citrus mitis, a tropical citrus
fruit from the Philippines. The triple hybrids which resulted were
called “Citrangequats” and “Citrangedins” respectively. The most
promising hybrid yet introduced is among the latter group and has
been named the Glen Citrangedin, from Glen St. Mary's, Florida, where
much of the breeding work has been done. It has small fruits about
the size and flavor of a lime, but colored like an orange. The rind is
without even a trace of the musky oil which characterizes the original
hybrid and the tree is hardy at least as far north as southern Georgia.
This artificial cosmopolite, uniting the possibilities of the Chinese
Poncirus, and Philippine Calamondin with the common orange, is the
“farthest north” which has as yet been achieved by the plant breeders.

Edgar Anderson.

Flowers and fruits of Poncirus trifoliata

Photographed by Herbert W. Gleason

48

Grafting

Die Veredelumj, a German horticultural term for which we, unfor-
tunately, have no English equivalent, is the ennobling, the refinement
of a plebian plant, the raising of a weed, tree or herb, to luxuriant
fruitfulness or beauty. Of the various methods of Veredehmg grafting
is one of the best known and most frequently employed. This art and
science has come down to us from beginnings lost in hoary antiquity.
Grafting was already an established procedure of horticulture in Bible
times. (See St. Paul’s Epistle to the Romans, Chapter 11.) Pliny and
Vi gil made frequent reference to grafting in ancient Roman horticul-
ture. Gradually the practice emerged from the magic and superstition
surrounding it; through the Dark Ages the Roman practices were re-
tained and improved by the European monks, until today we have a
heritage of the experiments and lore of two thousand years to guide
us in our use of grafting in plant propagation. Yet experiments and
observations in the past few years assure us that we have much to
learn regarding when and what and why and how to graft. It is the
object of this number of the “Bulletin” to point out some of the sig-
nificant and interesting aspects of grafting, although it is impossible
to do more than sketchily indicate the main features of a practice
concerning which many volumes have been written.

Why are plants grafted? This is a question which is frequently
asked by the amateur horticulturist and to which there are many
answers. Primarily, we graft to perpetuate a desirable variety which
has appeared as a sport on an otherwise normal plant or as a seedling
of uncommon worth. To propagate such a shoot or plant by seed
would mean, in nearly all cases, a reversion to the less desirable parent
form and consequent loss of the desired chaiEcter, or else it would
mean the loss of the prized variety in a host of variable and atypical
offspring. Vegetative propagation will preserve a stock which other-
wise would be lost to horticulture. But vegetative propagation includes
procedures other than grafting, as, for example, the rooting of cuttings
or of layers. Why, then, is grafting resorted to? Here many factors
come into play. In some cases such as Apple, Pear, Sorbus and Maple,
propagation by means of cuttings is impracticable because of the failure
of the wood to root with a satisfactory percentage of success. In other
cases, particularly where a large supply of the new variety is required,
grafting or budding are resorted to because of the saving of the mother
wood, since only one or two buds per plant are necessary in contrast
to the several buds of a cutting. Frequently there is an important
economic factor to consider; in cases in which the grafting method is
more rapid or more economical of labor or materials, the propagator
must employ the method most saving of expense and effort. Finally,
grafting may be used for purposes peculiar to a given plant. Thus the
European Grapes are grafted on American stocks because the latter
are resistant to the destructive Phylloxera . In such cases as the graft
of Almond on Peach, the grafted Almond attains a vigor nearly twice
that of the ungrafted Almond. Dwarfing, for increasing the produc-
tivity, for decreasing the time from propagation to fruitfulness, and
for producing certain desired ornamental effects, may be accomplished

49

by grafting, as, for example, the dwarfing of Pear on Quince. The
habit of a plant may be modified by grafting, a point of importance in
dealing with the shapeliness of ornamental shrubs. Grafting may ex-
tend the period of productivity of a tree or may be used to repair the
ravages of weather and parasites. Finally, grafting upon hardy roots
may permit the cultivation of certain plants in colder climates than
would otherwise be possible. All these and more advantages may re-
sult from the judicious selection and use of grafting stocks.

These, then, are the advantages of grafting. What are its disadvan-
tages, if any? One of the earliest arguments against grafting was
based on the conception that the grafted scion partakes of the quality
of the stock and that it may be more or less profoundly altered by the
character of the stock. Grafting was condemned in some cases because
it was felt that the scion lost its specific characters from the effects
of its foreign root system. From our knowledge at the present we
may say with assurance, however, that such direct stock effects are
comparatively rare and do not serve as a legitimate argument against
grafting in general. There is, however, one very important disadvan-
tage in injudicious grafting and that is the incompatibility resulting
from the grafting of ill-assorted stocks and scions. Such incompat-
ibility may result in pathological symptoms in the crown of a severe
order, as has been shown by the writer in Lilac grafted on Privet.
Other cases are known in which grafting upon certain stocks results
in a distinct loss of vigor or health of the scion. Fortunately, few
such ill-mated graft combinations are frequently employed in nursery
practice, but the discreet horticulturist should continually be on the
gjard against possible incompatibility in graft combinations.

What plants may be grafted? In ancient times it was believed that
any plant might be grafted onto any other regardless of botanical re-
lationships. Such weird graft combinations as Apple on Citron, Grape
on Cherry, Mulberry on Poplar or Beech, Pear on Ash or Maple, and
Oak on Elm have all been cited by the ancients as desirable graft
combinations, but as early as 1788 Duhamel du Monceau pointed out
that all species of trees cannot be grafted onto each other, such union
being possible only when there is a certain analogy between the stock
and the scion. This analogy or relationship commonly is delimited by
the botanical family. In general, we may say that plants of different
families graft only with great difficulty or not at all; plants of dif-
ferent genera within the same family can sometimes be successfully
grafted one on the other; plants of a given genus quite frequently
serve as satisfactory understocks for other species of the same genus;
while different varieties of the same genus can be inter-grafted as a
rule with a high degree of success. There are some interesting excep-
tions to these general rules. Thus Lucien Daniel, who has devoted a
long and fruitful scientific career almost exclusively to the study of
grafting, has reported successful grafting of plants of different fam-
ilies on one another, and there are cases in which inter-generic grafts
are more successful than inter-specific ones (the Potato succeeding
when grafted upon Datura and F*hy satis but not when grafted upon

50

Solanum pseudocapaicum). Similar cases in the Pomoideae may be
cited, the incompatibility of Apple on Pear being a classic example of
the failure of the union of closely related species.

Grafting we commonly associate with the propagation of woody plants.
However, many cases might be mentioned of the successful inter-graft-
ing of herbs. Although such combinations are for the most part of no
commercial importance they are of paramount importance in studying
the physiology of the graft union. The Solanaceae, the Crvciferae,
and the herbaceous legumes have been extensively investigated in this
connection. All of the plants with which grafting is usually connected
are, however, dicotyledons. Is it possible to inter-graft the monocoty-
ledons and the higher cryptogams? Although one would be tempted to
doubt the possibility of grafting plants without the dicotyledonous
type of conducting system, nevertheless recent research has shown
that it is entirely possible successfully to graft not only the monocoty-
ledons but certain of the cryptogams as well. Thus Daniel succeeded
in grafting Lilies, Gladioli, Vanilla, and other Orchids by using a graft
so cut as to permit a very long cut area of scion to lie in contact with
a correspondingly long area of stock. And finally he was able to
graft the cryptogam Selaginella arborea , while others have accomplished
the same even with fungi.

How should one graft? This is a question requiring such extensive
treatment that no attempt will be made to answer it here. There are
scores of techniques that may be applied, and the reader desiring in-
formation regarding these techniques is referred to any of the follow-
ing sources: Baltet.C., “L’art de Greffer” (Paris, 1907. An English
translation is also available.); 01brich,S.. “Vermehrung und Schnitt der
Ziergeholze” (Stuttgart, 1910); Bailey, L. H., “Cyclopedia of American
Horticulture”, section on “Graftage” (New York, 1903); Numerous
publications of the United States Department of Agriculture, supplied
on request.

It is hardly possible in the present brief summary of grafting to enter
into detail on the specific grafting requirements of the various woody
plants. The reader who wishes information upon this subject is recom-
mended to the more extensive treatises on grafting, several of which
(Baltet, Olbrich, Bailey, etc. ) give extensive catalogues of such data. Let
it suffice to suggest, however, a few general rules. The valid and fixed
species are usually best propagated by seeds. The perpetuation of hy-
brids and desirable sports is best accomplished, as a rule, by the use
of cuttings where these root freely. In those cases in which this is
not the case budding or grafting may be resorted to. A sound plan
to follow in budding or grafting such hybrids or sports is to use as un-
derstocks the parent varieties where these are available, otherwise to
use as close botanical relatives as may be obtained in sufficient quantity.
Plants which sucker freely should not be used as understocks, if it is
possible to secure stock varieties free from this habit, such stock sucker-
ing is evident for example, in Cotoneaster grafted on Crataegus, Hama-
melis grafted on H. virginiana, and Viburnum grafted on V. Lantana

fA Booke of the Arte and maner

|)0U) to ano <l5raffe all fortes of

trees ^ hoxv tofet jlones andfo^e T^epmSy
to ttiahe torlDe tries to graffe ori, asalfo rc«

medies and medicines. V V ith diuers ochec

neluc p;aaife«, lip one of tfje abbep of

Saint Vincentin Fraunce, praiflifed with
^10 otone hanbe0,tiemoeo into fCd'
ucn Chapter0, 00 thereafter
mo^tplapnelp Iballap-
pearc , an
aODition in
the

enbe of thi0 btokc, of certapne TDu teb p;iactiff0,
fet fCD^itb ano <ptigi fbeb, bp Leo-
nard MafcalJ.

In laudemincifionis diftichon,

Herpendum Campi quicquid Romanaque teliiis,
Frufiihcat nobis, incifione datur.

^Imprinted at London, for

lohn Wight. I 57J.

52

or V. dentatum. There are few fixed and absolute rules as to the time
and precise method of propagation. For this reason no one method can
be cited in particular cases to the exclusion of others. The propagator,
professional or amateur, is hence urged to consider the precepts of past
experience merely as bases from which may be developed by trial and ex-
periment numerous modifications and improvements more suitable to the
peculiar requirements of variety, environment, and commerce. It has
been the practice of the Arnold Arboretum to attempt many such
modifications. Some, as would be expected, have failed. Others, how-
ever, have proven to be highly desirable. Such experiences have all been
recorded and the examination of these records yields a wealth of useful
information for future procedure. Accordingly, the propagator is strongly
advised both to explore more thoroughly this field and to record an
account of his successes and failures that horticulture m.ay profit and
advance.

Kenneth S. Chester.

EXPLANATION OF THE PLATE

Facsimilie of the title-page of MascalPs treatise on grafting,
one of the earliest books in English on the subject.

ARNOLD ARBORETUM

HARVARD UNIVERSITY

BULLETIN

OF

POPULAR INFORMATION

SERIES 3. VOL. VI DECEMBER 28, 1932 NOS. 14 & 15

The Propagation of Woody Plants

For over fifty years there has been a steady stream of seeds and
cuttings coming into the greenhouses of the Arnold Arboretum. Some
of them originated nearby, many of them came from Europe or Asia,
a few came from other parts of the world. In our greenhouses they
have been changed into a returning stream of shrubs and trees and
vines for the Arnold Arboretum and for public and private collections
all over the world. Only those who have tried to propagate woody
plants will realize how well we have done with the material which has
come in. Trees and shrubs, unfortunately, are much more difficult to
grow from seed than are garden vegetables. Not only are they more
particular as to light and heat and moisture but each kind of tree or
shrub is fastidious in its own way. The following summary is, there-
fore, little more than a signpost, giving the general course one should
follow. To be complete it should include special recommendations for
each kind of tree which might be grown.

By the use of three greenhouses, kept at different temperatures, we
are able to satisfy the various requirements of our material. We use
a warm greenhouse, a cool greenhouse, and a specially designed pit
house. Certain kinds of seed are sown early: There are others
which lose their vitality quickly and which must be sown as soon as
they are ripe. To this class belong the Elms, Soft Maples, Poplars,
Willows, Oaks and Magnolias. They are planted during the late
spring, early summer and fall, and germinate that same season, all ex-
cept the Magnolias.

There is another class which must be sown outside. They have
seed coats so hard that actual freezing out-of-doors is desirable. Here
belong the Lindens, Hard Maples, Viburnums, Roses, Plums, and the
whole Walnut family including Walnuts, Butternuts, Hickories and
Bitternuts.

53

54

The cool greenhouse is kept at a night temperature of 40° to 50°.
In it we plant Catalpas, Ashes, Beeches, Lilacs, Cercidiphyllums, For-
sythias. Privets, all species of Vitis, and all the Legume family (Wis-
tarias, Black Locusts, etc.)

The warm greenhouse has a night temperature of 50° to 65°. It is
used for Hydrangeas. Spiraeas, Deutzias, Mock-Oranges, Rhododendrons,
Azaleas, and most other members of the Ericaceae or Heath family.

Our pit house is a greenhouse specially designed for use in wintering
woody plants at a temperature just above freezing. It is kept between
32° and 40°, so far as that is possible, and to achieve this end it is
built down into the ground. Because of its construction very little
artificial heat is necessary, although it is supplied with hot water pipes
for use during unusually cold weather. One door leads into the furnace
room in the basement under the potting shed and on cold nights it
is left slightly ajar, providing enough warmth to keep the house above
freezing. At the other end of the house a flight of steps leads to an
outside door. The pit is fifty feet long with a central walk, on each
side of which are three shelves.

In the pit house, after they have been planted in the fall, are stored
such seeds as Apples, Pears, Barberries, Aesculus, Magnolias, Oaks,
Birches and Chestnuts. In this low, even temperature they germinate
more readily than they would in a warmer greenhouse.

Two kinds of seed receptacles are used in the actual planting of the
seeds. Those which are going out doors are planted, before the ground
freezes, in shallow wooden flats. Those which are to go into the green-
house are planted in regular clay flower pots of various dimensions,
according to the number of seeds to be sown. A few kinds of seed
require special soil mixtures. Seeds of the Ericaceae or Heath family,
for instance, are planted in soil made up largely of peat and sand with
a very little loam. For most seeds the soil is made up according to
the following formula: one part sifted loam, one part well-rotted leaf
mold, and a good sprinkling of sand.

Before the seeds are planted they are well cleaned. This is partic-
ularly necessary if they have a fleshy covering, since such a covering
usually retards germination. Apples and Pears are quartered and the
seeds are removed. With such seeds as those of Davidia the outer
fleshy husk is carefully scraped away with an old knife. No seed
should be deeply planted, in fact some seeds such as those of Spiraea
and Rhododendron are planted on top of the prepared soil and left
uncovered. For most seeds the flower pot or flat is filled to the desired
height and firmed down with the hand. The seeds are planted on
the soil, are sprinkled lightly with sand, and are then just barely
covered with the prepared soil, which is again pressed down firmly with
the hands.

View in the new Pit House at the Arnold Arboretum

When the seedlinj^s come up they are pricked off into shallow wooden
boxes, as soon as they are lar^^e enough to handle. Boxes are used
rather than pottery pans since they are cheaper and since they do not
dry out so badly during the hot weather. The boxes are set close
together on the greenhouse benches for the summer. They spend the
next winter on the shelves in the pit house and early in the second
summer the young seedlings are planted out in rows in the cold frames.
Distances vary with the material but these rows are usually about nine
inches apart. They are kept well w'atered and during sunny weather
are shaded with removable lath screens. They are left out-of-doors
the second winter and receive no winter protection. During the next
spring they are moved into the nursery where they remain until they
are given a permanent place.

To fit these various activities into the routine of a year requires no
little experience. In sixty years the yearly round of duties at the
Arnold Arboretum has settled down into a fairly definite schedule.
It can be roughly summarized as follows:

Jan., Feb., Mar., Apr., May, June, July, Aug., Sept., Oct., Nov., Dec.

planting seeds (inside)

grafting

pricking off seedlings

planting nursery

care of nursery

planting seeds (outside)

cuttings

Since the material handled by the propagating department at the
Arnold Arboretum is of great scientific interest, it is necessary to keep
very accurate records of all the material which comiCs in, of all the
material which goes out, and of its behavior during the intervening
years. When seeds or cuttings come in they are listed in the acces-
sion book and are given a serial number. In the book is entered the
name of the species (if known), the place of origin, and the date re-
ceived. If the material came in as seeds, the date they are sown
and the date of germination is recorded. If it came in as cuttings,
the number of cuttings made is recorded and the number which root.
When the young seedlings are transferred to a row in the nursery
they are entered in the catalogue of the nursery, and when they are
sent away, either into the Arboretum proper or to other collections,
their destination is entered in the records. All of this information
is highly useful in many ways. It represents, in the bulk, whole
years of careful work by those who have had the records in their
charge. Only those who have helped to take care of a large collection
of living plants can realize how difficult it is to keep such records com-
plete and accurate. One can safely say that there are few other
collections, private or public, which approach the Arnold Arboretum’s
in the completeness and accuracy with which plant records have been
kept.

Edgar Anderson.
W. H. Judd.

INDEX TO SERIES 3 VOLUME VI

Synonyms are in italics; illustrations in black face type

Acer rubrum, 9

saccharinum, 9, 11, 16
Alders, 10
Alnus incana, 10
japonica, 10

— rugosa, 10
Amelanchier asiatica, 20

canadensis, 18, 20
grandiflora, 18
laevis, 18, 19
- oblongifolia, 18
Arbor-vitae, 12
Arnold Arboretum, Airplane

View, 39

Aspen, Large-toothed, 12

— Quaking, 12

Botanizing from an Airplane, 37

Cedar, Red, 14

— White, 12

Chamaecyparis thyoides, 12
Cherries, Early Flowering

Japanese and Chinese, 17
Citrus trifoliata, 45
Conifers, 12

Conifers, Winter Browning of, 8
Corylus Avellana, 10

— Colurna, 10
Cottonwood, 12
Crataegus, 25

— Arnoldiana, 26, 27
coccinioides, 28

— cordata, 28

— crus-galli, 28

— Lavallei, 28

— monogyna, 26

— Oxyacantha, 26

multiplex, 26

plena, 26

— persistens, 28

— phaenopyrum, 28
pinnatifida, 26

major, 26

— punctata, 28

— submollis, 28
Cuttings, 56

Daniel, Lucien, 49

Elm, American, 10
Washington, 8

— White, 10
Empress Tree, 24

Filbert, 10
Fire, 21

Flowering Habits of Trees

and Shrubs, 14

Grafting, 48

Grafting, Failure of Union, 50
Growing Oranges in Boston, 45

Hawthorns, 25
Hazel, European, 10

— Turkish, 10
Hazels, 10
Hedera colchica, 6
amurensis, 6

— helix arborescens, 6
baltica, 1

Hemlock Hill, Fire, 21, 23, 24,

Ivy, Baltic, 1

Juneberries, 18
Juniperus virginiana, 14

Larches, 12

Maple, Red, 9

— Scarlet, 9

57

58

— Silver, 9

— White. 9
Mascall’s Treatise on

Grafting, 51, 52

Orange, Trifoliate, 45

Paulownia tomentosa, 24
Peaches, 17
Finns pungens, 13, 16
Pit House, Arnold Arboretum, 55
Plum, Beach, 38
Poncirus trifoliata, 45, 47
Poncirus trifoliata hybrids, 46
Poplar, Canada, 12

— European Black, 12

— Lombardy, 12
Poplars, 10

Populus, balsamifera, 12

— canadensis, 12

— grandidentata, 12

— nigra, 12
italica, 12

— tremuloides, 12
Propagating Department, 56
Propagation of Woody Plants, 53
Prunus maritima, 38

Prunus maritima,

Distribution of, 41, '
Prunus Persica, 17
Pseudolarix amabilis, 35

Records, Propagating

Department, 56

Rosa Agnes, 33

— Alice Aldrich, 32

— Arnoldiana, 32

— Belle Poitevine, 34

— Blanc Double de Coubert, 32

— F. J. Grootendorst, 33

— Lady Duncan, 30

— Max Graf, 30

— New Century, 32

— Nova Zembla, 34

Rosa rugosa and its hybrids, 29
Rosa rugosa kamtschatica, 31, 36
X Rosa ferruginea, 33

— Ruskin, 33

— Schweidnitzia, 34

— Sir Thomas Lipton, 32

Seeds, Planting of, 54
Shadbush, Canadian, 18

— Gray-leaved, 18
“ Smooth, 18

— Swamp, 18
Shadbushes, 18

Shrubs, Flowering Habits of, 14
Spring Classes for 1932, 7

Thorn, Cockspur, 28
~ Dotted, 28

— Washington, 28
Thuja occidentalis, 12
Trees, Early Flowering, 9

— Flowering Habits of, 14

Ulmus americana, 10

Vandalism in the Arboretum, 22
Veredelung, 48

Willows, 12

Woody Plants, Propagation of, 53
Yews, 14

PUBLICATIONS FOR SALE AT THE
ARNOLD ARBORETUM OF HARVARD UNIVERSITY

JAMAICA PLAIN, MASS.

JANUARY 1, 1933

JOURNAL OF THE ARNOLD ARBORETUM. A quarterly journal

published by the Arnold Arboretum. Subscription price $4.00,
single numbers $1.25.

Vols. VMX (1925-28), and XI-XIII (1930-32) complete. Price $3.00
a volume, single numbers $1.00.

Vols. I-V and no. 3 of vol. X out of print.

CONTRIBUTIONS FROM THE ARNOLD ARBORETUM OF
HARVARD UNIVERSITY. A publication issued at irregular in-
tervals.

No. 1. The Hypodermataceae of Conifers. By Grant Books
Darker. 131 pp. 27 pi. June 15, 1932. Price $3.00

No. 2. Taxonomy and Geographical Distribution of the
Genus Milesia. By Joseph Horace Faull. 138 pp. 2 figs., 9 pi.
Oct. 1, 1932. Price $3.00

No. 3. Boraginaceae. By Ivan M. Johnston. 102 pp. Dec.
15, 1932. Price $2.00

No. 4. Ligneous Plants Collected in North Queensland for
the Arnold Arboretum by S. F. Kajewski in 1929. By C. T.
White. (In preparation.)

No. 5. Flora of Barro Colorado Island. By P. C. Standley.
(In preparation.)

BULLETIN OF POPULAR INFORMATION. Series 3, illustrated.
Issued during spring and autumn, about 18 numbers per year, to-
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A limited number of Series 2, vols. I-II (1915-16), VII (1921),
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at $1.00 each, single numbers $0.10 to $0.25.

THE BRADLEY BIBLIOGRAPHY. A guide to the literature of
woody plants, including books and articles in the proceedings of
learned societies and in scientific and popular journals, published
in all languages, to the end of the nineteenth century. Compiled
under the direction of Charles Sprague Sargent by Alfred Rehder.
4°. 5 vols. Cambridge, 1911-1918. Bound Price $40.00

Unbound Price $30.00

PLANTAE WILSONIANAE. An enumeration of the woody plants col-
lected in western China for the Arnold Arboretum during the years
1907, 1908, and 1910, by E. II. Wilson. Edited by Charles Sprague
Sargent. 3 vols. (9 parts). Cambridge, 1911-1917.

Parts 1-4 are out of print; the remaining parts each $1.50.

'I'lir] (;KM’S IMM'S. By (^kokoe Bi sseel Shaw. P. 96 pp. 39 pi.

( 1911. Price SI 0.00

oi nii: mbkaio oi nii: aknold akho-

KKTIM. (lonipilt'd inider tlie direction of (diaries Sprague Sar-
gent hy Kthei.yn Maih\ dAcKEU. P. 2 vols. (ianihridge, 19 Id-
1917.

\ 01. 1. Authors and titles. Unhound /Vzce S7.50

VOl. II. Subject catalogue. I nhound l*iice S7.50

- Supplement. (In press).

TIIK CIIKKUIKS OF JAPAN. By Ehne.st IIenhy Wilson. 8°. 68 pp.

8 pi. Cambridge, 1916. \\ ith supplement of 3 pp. Price S3. .50

THE COMFEKS AM) TAXADS OF JAPAN. By Ernest Henry
W ilson. 4°. 91 pp. 59 pi. (Cambridge, 1916. Price S5.00

JlIF FOREST TREES OF NEW EN(H.ANI). By Horert Green-
leaf Leavitt, viii + 179 pp. 1 pi., 2 maps, 78-^ 1 figs. sm. 8°.
Jamaica Plain, Mass., 1932. Price SI. 75

THE SIEVA OF NORTH AMERICA; a description of the trees which
grow naturally in North America exclusive of Mexico. By Charles
Spragi :e Sargent. W ith 740 plates drawn from nature bv Charles
Edward Eaxon. 14 vols. f°. Boston and New York, 1891-1902.

A few sets in which some pages in vols. I\ and XIV are supplied
hy photostat copies. Price S350.00

The same. Broken sets. Number of volumes and prices on request.

Complete sets of the 740 plates drawn from the '"Silva”. Price SIOO.OO

Selected plates (according to number). Price each SO. 50 to SI. 00
(CARDEN AND FOREST; a journal of horticulture, landscape art and
forestry. Conducted by Charles Sprague Sargent. 10 vols. 4°.
Illustr. New York, 1888-1897.

The following volumes can be supplied; \ ol. I (title-page and in-
dex missing).- Vol. II (only odd numbers).- Vol. Ill (bound in mo-
rocco).- Vol. IV (1 unbound and 2 bound copies).- Vol. V (3 copies). -
Vol. VI (1 complete copy and 1 lacking no. 254).- Vol. VH (2
copies).- Vol. VUl (3 copies).- \ ol. IX (3 copies).- Vol. X (1 com-
plete copy and 1 lacking no. 484).- Also odd numbers. (Numbers
and prices on request). Unbound volumes Price each $10.00

Bound volumes Price each $12.00
MANUAL OF CULTIVATED TREES AND SHRUBS HARDY
IN NORTH AMERICA EXCLUSIVE OF SUBTROPICAL AND
W ARMER TEMPERATE RECHONS. By Alfred Rehder.
xxxvii -|- 930 pp. 8°. New York, 1927. Price $10.50

(;UIDE TO THE ARNOLD ARBORETUM. 8°. 33 pp. 7 pL,

2 maps. Price SO. 50

POST CARDS; views of the Arnold Arboretum.

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