Today's Ramble was lead by Linda Chafin.
Here's the link to
Don's Facebook album for today's Ramble. (All the photos in this post are compliments
of Don.)
Today's post was written by Don Hunter, Linda Chafin and Dale Hoyt.
Attendees:27
Announcements:
Donderos' Kitchen is ceasing operation at the Botanical Garden next week.
Andrea Fischer,
the Garden's Volunteer & Tour Coordinator, has volunteered to fill the gap
and will make coffee for us next Thursday (Nov. 3), but we will have to bring
our own snacks. The Georgia
Center will be taking over the operation of the snack bar sometime next week
but we do not currently know when it will be open for business.
Next Wednesday
(Nov. 2) @ 9:00 AM Emily will lead a tree
walk at Sandy Creek Nature Center.
Today's reading: Linda
read a passage from The Triumph of Seeds:
[There are] any number of
metaphors in Genesis, many of them biological. The chapters concerning Adam and
Eve, for example, do more than de- scribe the dawn of humanity and original
sin. They also tell one of the greatest seed dispersal stories of all time.
From the Renaissance forward,
artists have made the scene in- delible: Adam and Eve sharing a luscious apple
below the Tree of Knowledge of Good and Evil, with a serpent coiled around the
closest branch. Botanical purists point out that such large-fruited apple
varieties didn't become common until the twelfth century, and that the fruit
should probably be a pomegranate. Whichever the species, the cunning snake had
chosen a perfect lure, something that evolved for the sole purpose of
temptation. To a hungry animal, the tiny seeds inside an apple or the stone at
the center of a date may seem irrelevant, secondary to the irresistible flesh.
But the truth is the other way around. Fruit, in all its magnificent variety,
exists for no other reason than to serve the seeds.
Whether a plant is growing in the
Garden of Eden, in a tropical rainforest, or in a vacant lot, its investment in
producing, nourishing, and protecting its seeds means nothing without
dispersal. Offspring that languish on the mother or drop directly below amount
to little more than a wasted effort. If they sprout at all, they won't survive
long in the shade of a fully grown parent. (In some cases, adults release
toxins into nearby soil to prevent their progeny from becoming competitors.)
For [most fruits], adding a thin layer of pulp to its seeds can entice
[animals] to carry them half a mile or more. The Tree of Knowledge did even
better. According to Genesis, eating that Forbidden Fruit resulted in Adam and
Eve's immediate expulsion from Eden. Metaphorically, at least, the fruit went
with them. Some depictions show the guilty couple still clutching a half-eaten
apple. And if it was indeed a pomegranate, then the seeds would have been
safely lodged in their digestive tracts. Either way, the Tree had put itself in
a great position. With that one tempting fruit, it went from a garden-bound existence to the promise of
mass dispersal with humanity across the face of the earth.
From:
Thor Hanson, 2015, The Triumph of Seeds,
Basic Books, pp. 182-184
Today's
route: We left the Arbor and took the cement walkway down to the access road,
then followed the road down to the bottom of the Dunson Native Flora Garden;
then returned through the DNFG, pausing along the way to search for and discuss
all the fruits we could find.
Our focus today was on fruits and seeds and we needed a little
introduction to some of the ideas and concepts centered around them. Linda
passed out a sheet illustrating and defining a variety of fruit types. If
you missed the Ramble or lost the handout you can find it at this link.
A University of Kentucky course has a series of excellent color illustrated
.pdf files depicting different fruit types. You can access these by downloading
a single file at this link. Once you get the
file, open it and click on the links inside to download the other fruit files.
Even if you aren't interested in all the terminology the spectacular diversity
of fruit types is mind boggling. I guarantee you won't be disappointed.
Note: A
reference I use for botanical terms is: Harris, JG & MW Harris, 2001, Plant Identification Terminology, 2nd
ed., Spring Lake Publ., Spring Lake, UT. All the definitions in this post
are in italics and are from that source.
A good definition of a fruit is: A ripened ovary and any other structures which are attached and ripen
with it. Like all definitions, the devil is in the details.
The University of Kentucky source cited above divides fruits into the
following useful categories:
Simple fruits
– A fruit derived from a single flower and a single ovary
Multiple fruits
– A fruit derived from a single flower and multiple, non-united ovaries.
Compound fruits
– A fruit from an inflorescence (more than one flower).
Accessory fruits
– Any of the fruits above that include additional tissues not derived from the
ovary. These tissues are usually floral or receptacle tissues, like bracts.
Nuts, acorns (A dry, indehiscent, one-seeded fruit
similar to an achene but with the wall greatly thickened and hardened. (Indehiscent
means: not opening at maturity along
definite lines or pores.)
Examples of
nuts: fruits of beech, chestnut, oak, hazel, walnut and hickory.
In beech, hickory, and walnut, this becomes confusing because the nuts
are surrounded by a husk that does split open. The husk is not actually part of the “nut” but is
“accessory tissue” derived from vegetative tissue of the parent plant, making
these a kind of Accessory, simple fruit.
Nuts, strictly speaking, are the part derived from the
fertilization process. It includes the embryo (future plant), the cotyledons
(food for developing embryo), and the pericarp (the fruit wall that develops
from the ovary). In nuts, the pericarp is usually hard and bony. The pericarp
is made up of three layers (endocarp, mesocarp, and exocarp), but in nuts these
layers are hard to tell apart.
In oaks, the acorn cap (or cupule) is the accessory
tissue derived from the bracts of the flower on the
parent plant. In beech and chestnut, the spiny covering of the nuts is the accessory
tissue. Accessory tissue surrounds the immature ovary as it develops into a nut
and persists on the mature nut as a husk that splits to release the nut. In the
drawing below the accessory tissue, i.e. the acorn cap, is shown.
 |
| Wikipedia illustration by KDS444 |
|
Similarly, in hickory, pecans, and walnuts, the outer
covering that splits open is accessory tissue. This is the thick “husk” on the
mockernut for example. The nut itself includes the hard, bony shell. (In pecans,
the shell is fairly thin and easily breaks open.) In the drawing below the husk
is not shown. In beech the spiny bur is accessory tissue and surrounds 1 or
more nuts.
 |
Hickory nut section
(Clipart) |
|
|
 |
| Beech nut |
|
 |
| Beech fruit with contained nuts |
|
Other fruits in other families also include accessory
tissue, e.g. strawberry. The red part is swollen stem tissue, the actual fruits
are the tiny, crunchy things.
Many
acorns were seen scattered across the red brick pavers at the Arbor. There was
some speculation as to the function of the cap and I suggested, tongue in
cheek, that it must be to hold the nut to the tree. Most of the acorns in this
area are from white oaks and northern red oaks. One of the Ramblers impressed
us with her talent whistling across the top of one of the acorn caps.
A note about
hickories in the Garden.
I have been confused as to the identity of some
of the hickories in the Garden for several years. In particular, I have had
trouble convincing myself that we have pignut hickory in the Garden. In 1998
the eminent Georgia ecologist Charles Wharton produced a survey of the natural
environments of the State Botanical Garden of Georgia. Here is what he had to
say about the pignut hickory:
Even most botanists
dread hickories. The SBG has at least four kinds. The most common appears to be
a hybrid between pignut (Carya glabra) and
sweet pignut (C. ovalis). This widespread tree
Dr. Bongarten calls a "hybrid swarm." . . .
The small nut and the thinner husk of the hybrid is distinctive (the
nuts are relished by squirrels).
The Dr. Bongarten referred to in the passage
above is Bruce C. Bongarten. He was Associate Dean of the UGA Warnell School of
Forestry and later became Provost of SUNY College of Environmental Science
and Forestry in New York.
Comparing hickory nuts and acorns:
The
husk on a hickory nut is equivalent to the cap on an acorn; both are derived
from tissue on the parent plant and provide a protective covering to the
developing nut. In hickories, pecans, and walnuts, the protective covering
persists on the nut. In acorns, the nut “outgrows” its protective cover, which
persists only as a small cap (though in some oak species the nut remains
covered by its spiny husk). The nut
inside the husk of a hickory nut is like the acorn held by the cap. The meat inside a cracked hickory nut is like
the meat inside an acorn; both are largely composed of cotyledons which nourish
the developing embryo and young seedling.
Linda showed the group hickory nuts in a side by side comparison. The smaller nut, with the thinner husk is a
pignut hickory nut. The larger nut, with
a very thick husk, was from a mockernut hickory.
 |
| Pignut x Red hickory nut with incomplete separation of husk sections |
 |
Comparison of Pignut x Red hickory nut (L) with Mockernut hickory nut (R)
Note size difference and thickness of husk |
Samara (A dry, indehiscent winged fruit.)
Examples of samaras: fruits of maples,
elm, ash, tulip tree.
At the first switch back in the sidewalk, we started
seeing Tulip tree samaras which were scattered over the walkway down to the
next two switchbacks. The large Japanese maple at the first switchback must
have shed its samara fruits earlier because we only found a few of them in the
mulch
Examples of legumes: fruits of the
bean family (Fabaceae) – Redbud, Baptisia (False indigo), Tall Indigo (Amorpha fruticosa), peas, beans.
 |
Seed (L) and seed pod (R) of Amorpha fruticosa
Although the seed pod does not split open (indehiscent) it is still a legume. |
We also found several brown, dried Baptisia seed pods. Most
were open and had lost their seeds but a few unopened pods remained. These rattled, with the enclosed seeds, when
shook. These seed pods are, by
definition, legumes, since they split open lengthwise into two halves.
Nearby was a tall indigo, a member of the
legume family, with hundreds of very small black pods. While its fruit is indehiscent, it is still considered a legume. Perhaps because of its small size, the pod is
eaten whole by animals. We crushe one, revealing a single, small black
seed.
Berry (A fleshy fruit developing from a single
pistil, with several or many seeds, as the tomato. Sometimes applied to any
fruit which is fleshy or pulpy throughout, i.e., lacking a pit or core.")
Beauty berry
 |
| Beautyberry seeds in a berry |
|
We stopped along the deer fence to look at several
American beautyberry shrubs that were sticking out from the fence. The once purple berries are now shades of
brown and somewhat soft and wilted looking.
Pressing an individual berry between the thumb and finger reveals two to
three tiny seeds, floating in the moist, pulpy interior. Each of the beautyberry fruits is, by
definition, a berry because it is juicy and fleshy and has multiple seeds.
Drupe (A fleshy, indehiscent fruit with a stony
endocarp surrounding a usually single seed, as in a peach or cherry.)
Examples:
Viburnum
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| Viburnum fruits |
|
We
passed by a viburnum with many clusters of red fruit. Each red berry is a drupe, containing a
single large seed.
Dogwood,
Next, we stopped briefly at a dogwood. The fruit were borne high up on unreachable
limbs but we were able to find some on the ground. The red color of the berries
attracts birds. The fruits are drupes, a single-seeded fleshy type of fruit.
Winterberry, Possum
haw
Back to the deer fence, we found a possum haw or
winterberry full of red fruit, each containing approximately three seeds in a
very moist pulp. Although these seem to meet the definition of “berry,” they
are technically considered a special kind of drupe. The fruit of this tree is
poisonous to humans although it is edible to wildlife.
Silverbell, Halesia
Someone produced the fruit of a four-winged silverbell
tree. We splayed back the wings and found a hard seed inside. According to this
site "The fruit is a dry, oblong, four-winged drupe that matures in
the fall."
Capsule (A dry, dehiscent fruit composed of more than
one carpel.)
A
carpel is a "simple pistil formed from one modified leaf, or that part of
a compound pistil formed from one modified leaf. Carpel number of a compound
pistil is determined by counting the number of stigmas, styles, locules and
placentae. Carpel number is indicated by whichever of these parts is found in
the greatest number.")
Camellia
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| Camellia flower and fruit |
|
In
the lower Shade Garden, we passed by several camellias and stopped to look at
the fruit, a type of capsule that splits into segments (a loculicidal capsule).
The fruit wall (pericarp) is tan and splits into 3 sections to reveal the
rounded seeds, which are covered with a dark seed coat. The seed, when crushed, revealed a cream
colored interior, the endosperm.
Sweet pepperbush, Clethra
 |
| Clethra fruits with retained styles and stigmas |
|
We
next looked at the fruit of a sweet pepperbush shrub. The tiny fruits were arranged along the
length of a raceme about three to four inches long. The styles were still present, extending from
the top of each fruit. The three stigmas were still visible on the tips of the
styles. These were the sites of
pollination. After pollination, the
pollen grew a tube down the style, releasing sperm cells into the ovary of each
flower. The fruits of sweet pepperbush
are septicidal capsules, which separate into three segments along the wall between
the fruit’s segments.
Trumpet vine
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| Trumpet vine seed capsule split open |
|
Down the road a short distance, we saw several green and
brown seed pods hanging from a trumpet vine growing up a large pine tree. We examined the brown, dried pods and found
that they were split lengthwise along both sides. Because of this, we thought the pod was a
legume. However, it turns out the fruit is actually a capsule that splits into
two segments. The thin, flat seeds were stacked inside the segments, each
bearing two wings for wind dispersal.
Hibiscus
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| Hibiscus seed capsule |
|
We examined several dried seed capsules from the hibiscus
bushes located in the Dunson Garden. The
five-sectioned fruits are loculicidal capsules.
Pepo (A fleshy, indehiscent, many-seeded fruit
with a tough rind, as a melon or cucumber.)
Passionflower
 |
| Passionflower fruit opened to show seeds |
|
Sue returned from the Dunson Garden with a
drying, shriveled maypop, the fruit of the passionflower vine. Opening the fruit, we saw many free hard,
dark seeds, each encased in a moist, gelatinous coating. The fruit is considered a pepo, a special
kind of berry that has a hard rind.
Several Ramblers commented on the pleasant smell emanating from the
fruit when it was opened. Don decided to
see what the pulpy seeds tasted like and found then both sweet and, at the same
time, sour....and also quite tasty. A related species of passionflower, Passiflora edulis, is used to flavor drinks and ice cream in the Caribbean and Latin America.
Achene (A dry, indehiscent fruit with a single
locule and a single seed(ovule), and with the seed attached to the ovary wall
at a single point, as in the sunflower.)
 |
| Seeds of Smooth coneflower are the dark structures between the pointed accessory tissues. |
Next to the hibiscus bushes is a smooth purple
coneflower, now gone to seed. We
examined several of the brown seed heads, and though they had lost most of
their seeds to birds, we could see a few seeds, classified as achenes, present
deep inside the bristly seed heads.
Non-flowering seed
plants
The
non-flowering plants that produce seeds are called Gymnosperms, which means
"naked seed." As the name implies, the seeds of gymnosperms are not
enclosed in an ovary. Instead they lie on the surface of modified leaves. In
the conifers, the dominant group of Gymnosperms, the reproductive structure is
called a cone. It consists of a spirally arranged set of modified leaves called
scales; the collection of cone scales forming the cone. In addition to the
conifers, the other gymnosperms are cycads, the ginkgo and a plant called
Gnetum.
The
cone is the functional equivalent of a flower. Each of the cone scales holds an
ovule (a potential seed) on its upper surface. If pollen blown from a male cone
lands on a female cone scale a seed will develop on the surface of the cone
scale. Gymnosperms are a more ancient group of plants than flower & fruit-bearing
plants. Fruits are produced from the ovaries of flowers and typically enclose
their seeds in a covering that encourages seed dispersal by animals, or water,
or wind, etc.
 |
| Pollen-bearing cones of Eastern red cedar just beginning to develop. |
We
took note of two gymnosperm reproductive structures today: an aborted Loblolly
pine cone, too small to contain seeds, and the yellowish tips of branches of an
Eastern red cedar. Those branch tips will develop into pollen producing male
cones by spring.
Seeking What We
Find
As we made our way back through the Dunson garden, Ed
found an “owl pellet.”
 |
| Owl pellet |
Owls and other
predatory birds, like hawks, cannot digest hair, bones, feathers, teeth or
insect exoskeletal material. After the other parts are digested these indigregurgitated
in the form of a compressed pellet. It is possible to determine what the bird
was eating by examining such pellets. A reference collection is necessary to
make such identifications.
 |
| Bony contents of the owl pellet |
|
Ed pulled the pellet apart and discovered small
bones, including a tiny jaw bone, complete with teeth. It was clearly the bones
of a small rodent.
I discovered an aborted hickory fruit with a small hole
in the husk. Don was not in sight to photograph it, but Angeli was. Such holes
are the result of a beetle grub feeding on the seed inside the nut. Earlier in
the spring the adult beetle, a type of weevil in this case, lays an egg on the
ovary of a hickory flower. As the seed develops the egg hatches and the larva
feeds on the nutritious contents. When the fruit falls the grub eats its way
out, leaving a small exit hole, and pupates in the soil.
There
is an ant in the genus Temnothorax
that uses such emptied nuts as a nest, creating a small colony of approximately
one hundred individuals. When Angeli and I looked inside the hole we saw
movement and one of the ants emerged while I was holding the fruit. Angeli managed to get a photo of the tiny ant. Nothing
goes to waste in nature!
 |
| Temnothorax ant surveying its domain. |
Time up, we made our way back to the Arbor and some of us
gathered at Donderos' for the last time. (Not for us – for Donderos' Kitchen at
the Garden.)
SUMMARY OF
OBSERVED SPECIES:
Common Name
|
Scientific Name
|
White
Oak
|
Quercus alba.
|
Northern
Red Oak
|
Quercus rubra
|
Japanese
maple
|
Acer palmatum
|
Tulip
tree
|
Liriodendron
tulipifera
|
Eastern
redbud
|
Cercis canadensis
|
American
beech
|
Fagus grandifolia
|
Pignut
x Red hickory hybrid
|
Carya glabra x ovalis
|
Mockernut
hickory
|
Carya tomentosa
|
Loblolly
pine
|
Pinus taeda
|
Virburnum
|
Virburnum sp.
|
Sasanqua
camellia
|
Camellia sasanqua
|
Sweet
pepperbush
|
Clethra alnifolia
|
American
beautyberry
|
Callicarpa
americana
|
Flowering
dogwood
|
Cornus florida
|
Holly
|
Ilex sp.
|
Trumpet
vine
|
Campis radicans
|
Four-winged
silverbell
|
Halesia
tetraptera
|
Possum
haw or winterberry
|
Ilex verticillata
|
|
|
Purple
passionflower
|
Passiflora
incarnata
|
Hibiscus/Mallow
|
Hibiscus sp.
|
Smooth
purple coneflower
|
Echinata
laevigata
|
Blue
false indigo
|
Baptisia australis
|
Tall
indigo
|
Amorpha fruticosa
|
Eastern
red cedar
|
Juniperus
virginiana
|
