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Seed Dispersal

Myrmecochory: Seed Dispersal by Ants

8-6-14  myrmecochory 014As a dispersal mechanism, some plants have fatty structures called elaiosomes attached to their seeds’ coats which are very appealing to ants. After collecting a seed and carrying it back to its underground nest, the ant eats the elaiosome (or feeds it to ant larvae) and discards the intact seed in an area where waste and dead ant bodies are stored. Germination is highly likely in such an ideal environment, making myrmecochory a win-win situation. Trillium, bloodroot and violets are some of the thousands of plants that have elaiosomes attached to their seeds.

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Miterwort Flowering

5-28-14 miterwort _0328Miterwort, also known as Bishop’s–cap, is named for the resemblance of its fruits to the hats (known as miters) worn by bishops of the Roman Catholic Church. If you examine a flower closely, you will see its delicate, 5-pointed, snowflake-like beauty. Each flower is in the shape of a tiny cup, with dissected petals arising from the rim of the cup, resembling fine lacework. There is a glandular ring of nectar-producing tissue inside the cup which attracts small bees, flies and ants. Once pollinated, the flowers produce open seed-containing capsules. Water, not animals, is the dispersal agent for Miterwort’s seeds. The capsules orient themselves so that their opening faces upward. When it rains, the falling rain drops splash the seeds out of the capsules, dispersing them up to three feet away from the parent plant. The distance traveled by the seeds is dependent upon both the size of the raindrop and the distance that it has fallen before landing in a capsule.

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American Yew Female Cones

12-20-13  American Yew female cones IMG_6118Being a gymnosperm (its seeds are not enclosed in an ovary), American Yew, Taxus canadensis, lacks true flowers or fruits and possesses separate male and female (seed) cones. Each male cone produces up to 100 pollen sacs or more. The modified female cones do not resemble the typical woody cones of evergreens. Yews are the only conifers that produce seed cones that consist of a fleshy (and mucilaginous), scarlet, cup-shaped structure called an aril, each of which holds one seed. The seeds (not the aril) are poisonous to humans, but thrushes, waxwings and other birds consume them and aid in their dispersal.

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Thimbleweed Seeds Dispersing

11-29-13 thimbleweed 033Although it has a beautiful white flower, Thimbleweed, Anemone virginiana, is not as noticeable in the summer as it is when its seeds mature in the fall. Looking like a small ball of cotton, its thimble-shaped seedhead consists of a cone covered with tiny dark hooks that white, fluffy seeds cling to and cover until the wind carries them away from the parent plant. The seedhead of this member of the Buttercup family looks very much like that of its close relative, Long-head Thimbleweed, Anemone cylindrica, except A. cylindrica’s seedhead is slightly longer. As impressive as these eastern species are, there’s a species of Thimbleweed out West whose seedhead is so big the plant is referred to as “Mouse on a Stick.” In the summer, plant-eating animals usually leave Thimbleweed alone because the foliage contains a blistering agent that can irritate the mouth parts and digestive tract.

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White-throated Sparrows and Winged Euonymus

10-17-13 white-throated sparrow 125Although the breeding and winter ranges of White-throated Sparrows overlap, most, if not all, populations are migratory. During their flight southward in the fall, White-throated Sparrows stop during the day to refuel on seeds, fruits and insects, if available. Winged Euonymus (Euonymus alatus), or Burning Bush, is an invasive shrub that, in addition to shading and crowding out native plants, produces vast quantities of capsules, each containing up to four seeds. White-throated Sparrows and many other bird species find these bright red seeds attractive, but unfortunately, they are of little nutritional value to the birds and other wildlife that feed on them. How ironic that these birds, whose health and migratory success may be compromised by the seeds of this invasive plant, are facilitating its establishment by dispersing its seeds.

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Red Squirrel Gardens in the Woods

6-4-13 sugar maple seedlingsi 036Red and Gray Squirrels remain active year round, and thus, need to have access to food throughout the year. In order for this to happen, seeds and nuts must be stored in the warmer months for consumption during the winter and early spring, when food is much harder to find. While Gray Squirrels tend to bury nuts and seeds individually for this purpose, Red Squirrels often cache numerous seeds (mostly conifers and maples) in one spot, dispersing these caches throughout the woods. During the winter Red Squirrels use their memory (and sometimes their sense of smell) to locate these buried treasures. Inevitably some are overlooked and in many of these cases, the seeds germinate. Finding little patches of multiple seedlings, such as this miniature stand of young Sugar Maples, is a good indication that at least one Red Squirrel overwintered in the vicinity.


Aspen “Snow”

5-27-13 poplar fruit 004Even though it snowed in Vermont this weekend, there is something else white and fluffy that is also being blown about, and it doesn’t melt when it hits the ground. The tiny white bits of fluff that are floating in the air are the seeds of aspens (also referred to as poplars), primarily Bigtooth Aspen (Populus grandidentata), that are borne in capsules that develop along a 3 to 6-inch dangling stem. These former flower clusters, and the capsules and seeds they developed into, are referred to as catkins. The capsules split apart when the seeds are mature, releasing the cottony-tufted seeds that are well-designed for dispersal by the wind. Looking into the fluff-filled sky, it’s not hard to believe that a single Bigtooth Aspen tree can produce over a million seeds.


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