Ramble Report October 27 2016

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.

Visit this page to see other Announcements.

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

A single samara from a Tulip tree
the seed is at the right

Clusters of Tulip tree samaras

Red maple samara

Trumpet vine samaras

Legume (A dry dehiscent fruit derived from a single carpel and usually opening along two lines of dehiscence, as a pea pod.

Examples of legumes: fruits of the bean family (Fabaceae) – Redbud, Baptisia (False indigo), Tall Indigo (Amorpha fruticosa), peas, beans.

Baptisia seed pod, a legume

Redbud seed pod, a legume

Baptisia seed pod, opened to show seeds

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

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

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

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

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