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Welcome to bobklips.com, the website of Bob Klips, a plant enthusiast living in Columbus, Ohio.

Rattlesnake fern has huge sporangia!
Delaware County, Ohio
May 26 and June 7, 2009

Rattlesnake fern, Botrychium virginianum, is an especially large, common, and early-sporing type of grape fern. It is named for the tightly branched rattle-like cluster of spherical sporangia. The lower portion of the leaf is quite lacy (thrice-compound).

Rattlesnake-fern. May 26, 2009.
Delaware County, Ohio.

The "grape ferns" (genus Botrychium in the "succulent fern" family Ophioglossaceae) are unlike most other ferns. They don't develop the familiar fernish (fernish?) coiled-up bud known as a "fiddlehead," as the leaves spring up straight from the soil. Their spore cases (sporangia) are found not on the undersurfaces of normal-appearing leaves, but in terminal portions of the leaf devoted entirely to spore production. (Several other ferns do that too.) Most distinctively, however, the grape ferns bear sporangia that are especially large, indeed reminiscent of a cluster of grapes.

rattlesnake-fern sporangia
Rattlesnake-fern sporangia. May 26, 2009. Delaware County, Ohio.

Another distinctive succulent fern trait is the manner in which the sporangia dehisce (open) to release the spores. They open by a transverse slit. This is regarded as a primitive character, as it is a simpler structure than that of most other ferns, which have a belt-like annulus that splits the sporangium and often hurls the spores as well. Here's what the rattlesnake fern sporangia look like now that they are opening. Note the slits.

rattlesnake-fern sporangia
Rattlesnake-fern sporangia. June 7, 2009. Delaware County, Ohio.

Violet's hidden marriage...to herself! (himself?)
(cleistogamous flowers of Viola)
Highbanks Metro Park, Delaware County, Ohio
May 28-29, 2009

The springtime violet (genus Viola, family Violaceae) flower is showy, with large colorful petals. Perched upon a wiry leafless stalk, it has a striking bilateral symmetry. An expansive lower petal serves as a bee landing platform, while lateral petals confine the visiting insect to a path that encourages the collection and deposition of pollen. Purple veins serve as "nectar guides."  

Here's one, the downy yellow violet, Viola pubescens, as it appeared in a Delaware County, Ohio, woods approximately three years and six weeks ago.
Note at the bottom of the photo there is a flower bud, with the colorful corolla (petals) just beginning to poke out from the protective calyx (sepals).

downy yellow violet
Downy yellow violet in spring.
Delaware (Ohio) Wildlife Area. April 16, 2009.

Here's downy yellow violet as it appears now, conspicuously bearing fruits from the early spring flowers -- dry capsules filled with fairly large seeds that are dispersed by ants.

downy violet fruits
Downy yellow violet. May 27, 2009. Highbanks Metro Park. Delaware County, Ohio.

It certainly appears as though violet has stopped blooming now that the canopy is closed and the woods are shady. But violets "secretly" continue blooming during late spring and summer with tiny flowers that lack petals, never actually open, and self-pollinate. These are cleistogamous ("hidden marriage") blossoms, and they constitute the basis of most of the plant's annual seed output. The picture below shows (slightly left of center) one such cleistogamous flower. It looks like a bud, but it's a flower...as big and showy as it ever gets. (On the upper right a young fruit is developing from the self-pollination of another cleistogamous flower.)

cleistogamous flower and fruit
Downy yellow violet cleistogamous flower and fruit.
May 29, 2009. Highbanks Metro Park. Delaware County, Ohio.

Here's a studio shot of the same thing. One or two foreground stipules (stipules are paired leaf-like appendages that appear at the base of some leaves) has been removed to better show the flower.

cleistogamous violet flower and fruit
Cleitogamous flower and fruit of Viola pubescens.

In these cleistogamous flowers, only the lower two stamens --the ones that come into contact with the stigma --are well developed; the other 3 are rudimentary, lacking anthers. Like scandalous shots on the cover of a sleezy grocery store tabloid, the picture below shows a flower from which three sepals have been removed to expose Violet's secret marriage. Note the wooly ovary topped by a short curved stigma that is nestled snugly against a pair of stamens (one visible, just barely). Not only do these flowers not open, but even the stamens don't open or actually release pollen. The pollen grains germinate within the anthers. The resulting pollen tubes grow out through the upper anther wall, directly into the stigma!

cleistogamous violet flower
Partly dissected cleistogamous flower of Viola pubescens.

Viola pubescens comes in two varieties, differing in the pubescence of the ovary. It seems that most of the plants in our area, including the one above, represent the form with a white-hairy-ovary, var. pubescens, while a smaller proportion of the plants have a completely glabrous (hairless) ovary that is characteristic of var. peckii.

cleistogamous violet flower
Cleistogamous flower of Viola pubescens var. peckii. Foreground sepals removed to expose the
sexual parts of the flower. One stamen has been teased away from the pistil to show its structure.
Note the broad filament extending beyond the anther-sacs.

The showiness of the early spring violet flower is a mechanism to promote outcrossing, i.e., mating with other  individuals, possibly over great distances. Compared to self-pollination, outcross-derived offspring are generally superior. But outcrossing comes at a cost, because the structures required to attract and reward bees deplete resources that could be used for other purposes, such as making more seeds. Also, pollinator-mediated reproduction is unreliable. If bees are scarce, then the violet might have few children. To achieve both benefits --genetic variation AND multiplication --many organisms have separate components of the life cycle devoted to each. For the violet, the showy flowers serve to generate genetic variation, and the cleistogamous ones serve to produce a great number of fairly uniform offspring.  

Some wind-pollinated plants
Columbus and Tipp City, Ohio
May 23-24, 2009

Narrow-leaved plantain (Plantago lanceolata, family Plantaginaceae) is an annoying weed in lawns and other grassy places, as well as a pioneer in disturbed sites that aren't lawns. Plantain graces our roadsides, providing drivers with an interesting diversion from such mundane items such as other cars, red lights, stop signs, pedestrians, etc. 

row of plantains
Narrow-leaved plantain in median strip of Columbus roadway. Mar 23, 2009.

Plantain is a perennial herb with a basal rosette of narrow leaves, and many tiny flowers packed into spikes atop wiry scapes (leafless stalks with flowers at the top).

narrow-leaved plantain and cars
Narrow-leaved plantain in median strip of Columbus roadway. May 23, 2009.

Narrow-leaved plantain flowers are protogynous ("female first"). They develop sequentially from the bottom of the spike towards the top. Hence the upper flowers are in the (earlier) female phase while the lower, older, ones have "been there done that" with respect to the female thing, and are now presenting stamens.

plantain spikes
Plantain spikes. May 23, 2009. Columbus, Ohio.

Plantago flowers are 4-merous, with a calyx of 4 sepals, a corolla of 4 fused petals, and 4 stamens long-exserted on very slender filaments. The pistil consists of 2 fused carpels, topped by a stigma that is unbranched but, as is often the case with wind-pollinated stigmas, is somewhat plumose (feathery) to catch pollen grain whisking about.

MOUSEOVER image to see flower details
plantain flowers
Plantain flowers are protogynous, 4-merous, packd into compact spikes atop wiry scapes.

Although at first it sounds crazy, the plantain family is taxonomically closely related to the snapdragon (figwort) family, Scrophulariaceae. Indeed, modern treatments consider them to be scrophs! But if you compare these flowers to the 4-merous speedwell from last week (scroll down), it doesn't seem quite so far-fetched. (The 4-merous state of these scrophs is believed to be derived from a basic 5-merous plan, by the fusion of two lobes.)

Nearby, orchard grass (Dactylis glomerata, family Poaceae) occurs along the same road.

orchard grass
Orchard grass in roadside median strip.
Columbus, Ohio. May 22, 2009.

Orchard grass produces its flowers in distinctive fist-like clumps at the ends of side-branches that  project squarely off the main stem.

orchard grass flowers
Orchard grass flowers. Columbus, Ohio. May 22, 2009.

Grasses produce much-reduced flowers that entirely lack sepals and petals. The flowers are enveloped by paired tiny scale-like bracts.
A grass bears stamens with large anthers at the ends of long slender filaments.  Feathery pollen-receptive stigmas peek out from the paired bracts.

MOUSEOVER the IMAGE to see lower right area magnified, showing feathery stigmas
orchatd grass flowers
Orchard grass bears stamens with large anthers at the ends of long slender filaments.
Feathery pollen-receptive stigmas peek out from the paired bracts.

Meanwhile, a few counties to the southwest, in a woodland in lovely Miami County, a sedge is setting fruit. This is Davis's sedge, Carex davisii (family Cyperaceae). Like all carices (yes, for some insane reason that is the plural of "Carex"), the flowers are unisexual, and the plants are monoecious (a given plant produces both male flowers and female ones). They are spirally arranged, and the relative positions of the male and female flowers is of diagnostic significance. Here, the staminate (male) flowers are produced at the base of some spikelets that, at their tip, produce female flowers (and eventually small one-seeded fruits called "achenes").

Davis's sedge showing terminal spikelet that is staminate at
base, pistillate at top. May 23, 2009. Tipp City, Miami County, Ohio.

Sedges in the genus Carex have their female flowers, and ultimately the fruits, enclosed in a papery sac, the perigynium. The style extends through a small orifice at the top of the perigynium, and the style branches spread just above the perigynium to catch wind-borne pollen. In the studio portrait below, one perigynium is opened to show its stucture and reveal the achene and its persistent style. Note also that each flower (including the perigynium if it is pistillate) is subtended by a scale-like bract.

Davis's sedge showing perigynium opened to reveal achene inside.  

At the edge of the woods, a hickory tree is releasing pollen from its numerous staminate catkins.

Shellbark hickory, with a little musical encouragement, sends pollen into the world.
May 22, 2009. Tipp City, Miami County, Ohio. 

Blue Flags
Marion, Ohio. May 22, 2009

Irises (genus Iris, family Iridaceae) are perennial monocots with sword-shaped leaves and very showy flowers subtended by spathe-like bracts. A patch of large and strikingly beautiful blue flag iris stems is growing alongside a small pond at the Larry R. Yoder Prairie on the campus of Ohio State-Marion.

iris plants
Iris flowers alongside pond in Marion, Ohio. May 22, 2009.

Iris flower structure is surprising. Instead of having green sepals like most flowers, the outer perianth segments (3 sepals) as well as the inner ones (3 petals) are colored. (The sepals are somewhat larger than the petals.) Big whoop, you say...almost all members of the lily family (Liliaceae, with their "tepals") are like that, right?  But wait there's more. If you call right now, using the toll-free number at the bottom of your screen, we'll send you, absolutely free, three style branches that also petaloid! The expanded colorful styles arch over and run closely parallel to the sepals.

iris flower

Iris flower. Marion, Ohio, May 22, 2009.

As each style branch runs closely over a sepal, a copiously pollen-producing stamen lies sandwiched between the two of them. As its pollinator --some type of bee --forages for nectar at the base of a sepal, she slips beneath the stamen/style part of the sandwich, depositing pollen on the stigma, and picking some up from the stamens.

iris style
Iris style folded up slightly, revealing stamen between style and sepal. May 22, 2009, Marion, Ohio.

Irises have an inferior ovary, i.e., it is situated below the other flower parts. From the outside it looks merely like a swollen pedicel, but a cross-section reveals the ovules (future seeds) within. This photo shows a flower with all parts removed except for the pistil, and the ovary sectioned lengthwise to reveal the ovules within,

iris cross-section
Iris with ovary longi-sectioned.
May 22, 2009. Marion, Ohio.

What species of iris is this? It doesn't seem to match any either of the two possible native blue Iris species, as the sepals lack the pubescent (hairy) orange blotch at their base diagnostic of the southern blue flag,  I. virginica, yet the ovary seems a bit too long --approx. 3 cm as opposed to 1-2 cm  --for it to be the northern blue flag  I. versicolor. Maybe its a garden escape, or the blotch is there, but indistinct.

Incidentally, although these pretty blue flags were seen along the shore of a pond, blue flags are also sometimes seen in woodlands, especially ones where plant ecology research is underway.

blue flags
Woodland blue flags. April, 2008. Delaware County, Ohio.

A cute fruit
--purslane speedwell--
Pleasant, Marion County, Ohio. May 15, 2009

The genus of wildflowers (Veronica) collectively termed "speedwells" are members of the snapdragon family (Scrophulariaceae). With their nearly equal-sized (actinomorphic) and spread-out (rotate) petals, they don't look very much like snapdragons or most other members of the Scrophulariaceae, the blossoms of which are often strikingly bilateral and tubular. Several speedwell species are low-growing but aggressive agricultural weeds, including this one seen at the edge of a newly-plowed farm field in Marion County, Ohio -- purslane speedwell, V. peregrina.

speedwell with insect
Purslane speedwell. May 15, 2009.
Pleasant Township Park, Marion County,Ohio.

The speedwell fruit is a winsome little Valentiney heart-shaped capsule, surrounded by 4 sepals, and topped by a remnant of the style. 

speedwell fruit
Purslane speedwell fruit. May 15, 2009. Marion County, Ohio.

Nearby, one of our most common sedges, the loose-flowered woodland sedge (Carex laxiflora, family Cyperaceae) is growing. This species bears wholly separate staminate (male) and pistillate (female) spikelets. This specimen's single staminate spikelet is the brownish-green spear-shaped item extending above the top of the plant, while the other three, bright green, spikelets are pistillate.

loose-flowered woodland sedge
Loose-flowered woodland sedge. May 15, 2009. Marion County, Ohio.

Sedges in the genus Carex are distinguished by having their small dry one-seeded fruits (achenes) enclosed in an expanded bag-like structure, the perigynium. At this stage (late flowering, with fruits not ripe yet) the 3 filiform styles are visible extending out from the narrow orifice at the top of each perigynium.

sedge flowers 
Loose-flowered woodland sedge. Marion County, Ohio. May 15, 2009.

Dirty trees!
(stuff that falls off trees that isn't leaves)
Shumard oak --May 9, 2009
In the Clintonville neighborhod of Columbus, various red oaks --the sub-genus of oaks that have bristle-tipped leaves (unlike the rounded lobes of the white oak group), and acorns that take two years to mature (white oaks only take one year) --are common as street trees. Pin oak, northern red oak, and Shumard oak are all present. Like many trees, the oaks are wind-pollinated, and produce their numerous tiny male flowers in drooping catkins. These litter the gound after the pollen is shed.

Shumard oak (Quercus shumardii, family Fagaceae), one of the largest red oaks, has a generally southern and coastal plain distribution. It extends very sparingly into southwestern Ohio. It does well as a street tree.  Until 18 years ago when it was stuck by lightning, Ohio's largest specimen lived in a backyard just 2 blocks away from this tree-lind street, so I think these are Shumards. The leaves look right.

shed catkins of red oak
Shed staminate catkins of possible Shumard oak. May 9, 2009. Columbus, Ohio.

A lot of trees have been litterbugs this spring. For the latest, follow this link (a new page on the "Dirty Trees" section of this web site).

dirty trees link

Crusading crucifers! Marauding mustards! Messes of cresses!
(Various roadside Brassicaceae and a lovely woodland native one)
(...and a cameo appearance by springtails...)
Very late April and the 1st week of May, 2009
Delaware and Marion Counties, Ohio

The plant family Brassicaceae (mustard family) is easily recognized. Also known as Cruciferae --"cross-bearing" --the 4 separate and equal-sized petals set its members apart from most other plants flowering now. There are 78 mustards in Ohio, making it the 6th most specious family. Many of them are spring-flowering field and roadside weeds. This week, vast expanses of cropland waiting for the season's plowing and planting are covered with alien mustards. One of them constitutes great swathes of yellow. This is early winter cress, Barbarea vulgaris.

early winter cress
Early winter cress. May 1, 2009. Delaware , Ohio.

Early winter cress is recognized in part by its deeply divided lower leaves and elongate racemes of yelllow flowers. It is a usually a biennial, over-wintering as a rosette of leaves with a modest taproot storing resources drawn upon by the plant to flower abundantly so early in the season.

early winter cress
Early winter cress. May 1, 2009. Delaware, Ohio.

Flowers of the Brassicaceae have 4 separate sepals, 4 separate petals, and six stamens (barely visible in one of the flowers below).
winter cress flowers
Earlywinter cress. May 1, 2009. Delaware, Ohio.

Mustard family members have an unusual fruit type, a weird 2-chambered capsule with a partition inside that cuts across, rather than separating, the individual units (carpels) of which it is composed. That is a technical distinction, all but invisible, but it gives the mustard fruit its own special name, the silique. To be more specific, the term silique is used when it is long and narrow (sleek? ...evident in the fuzzy background in the winter cress closeup), while short squat siliques are called silicles. Appearing alongside the winter-cress are two more weedy mustards, both of which produce silicles: field peppergrass (Lepidium campestre), and field penny cress (Thlaspi arvense).

Field peppergrass. May 1, 2009. Delaware, Ohio.

Field penny cress siliques are much larger than those of peppergrass.

Field penny cress. Delaware Ohio. May 1, 2009.

In adjacent Marion County field penny cress consitutes great swathes of white.

Thlaspi arvense
Field penny cress. Marion, Ohio. May 8, 2009.

Tumble mustard (Sisymbrium) is a low-growing yellow-flowered annual weedy mustard that produces the sleekest siliques imaginable. Moreover, it disperses as a tumbleweed! After maturity the entire plant breaks away from the ground and is blown across the landscape, distributing seeds along the way.

tumble mustard
Tumble mustard. May 8, 2009. Marion, Ohio.

tumble mustarf flowers
Tumble mustard flowers and young fruits. May 8, 2009. Marion, Ohio.

Not all mustards are weeds. There are some lovely native wildflowers. One of them is smoth rock cress, Arabis laevigata, seen growing on a shale ledge in the woods at Highbanks Metro Park in Delaware, Ohio.

smooth rock cress
Smooth rock cress. April 28, 2009.

Smooth rock cress is also called "sickle-pod" as is siliques are extremely long and elegantly curved.

Arabis fruits
Smooth rock-cress developing fruits. April 28, 2009.
Highbanks Metro Park, Delaware, Ohio.

While the smooth rock cress was flowering 15 miles away, but really having nothing to do with the mustard family of plants, springtail insects clambered about a mossy landscape on a little brick wall in Columbus. The moss isTortula papillosa. Can anyone ID the springtails?

Woodrush (Luzula multiflora) --the other graminoid!

Hocking County, Ohio
May 1, 2009

"Graminoid" is a general term for any grasslike plant, a member of one of three families characterized by narrow stems, linear leaves, and tiny wind-pollinated flowers. Comprising the order Poales within the monocots, these include actual grasses (family Poaceae), sedges (Cyperaceae), and rushes (family Juncaceae). Of the three, rushes are the least numerous and thus not as generally well known as grasses or sedges. There are two rush genera in our area: Juncus ("rush" in the strict sense with many seeds per capsule and plants hairless) and Luzula ("woodrush," with only 3 seeds per capsule and plants more or less hairy). In an open mixed hardwood forest at Deep Woods Preserve in southern Ohio's Hocking County, common woodrush (Luzula multiflora) is currently blooming.

Common woodrush. May 1, 2009. Hocking County, Ohio.

The flower of a rush, unlike the highly modified flower of a grass or sedge, is fairly straightforward. Although the Juncaceae isn't placed especially close to the lilies (Liliaceae) in a modern classification scheme (they're in different taxonomic orders), it sure seems like it should be! Indeed, older manuals placed the Juncaceae alongside the Liliaceae in the Order Liliales. A rush flower looks exactly like a lily flower in perfect wind-pollinated miniature. Each has a superior ovary, regular symmetry, a perianth of three separate sepals and three separate petals that resemble one another ("tepals"), an androecium of 6 stamens, and a syncarpous gynoecium composed of three carpels topped by 3 stigma branches developing into a capsular type of fruit with 3 chambers (locules). The flowers practically scream "Lily"! (Or at least whisper it, as they are quite small.) I don't get it. If dodder is a miniature morning-glory, why aren't rushes miniature lilies?

Here's a closeup of the woodrush flower cluster. Note the flower parts in threes or multiples thereof (six stamens). Emerging from within each ring of stamens is the style with three feathery pollen-receptive stigmas. This appears to be an instance of protogyny ("female first") wherein the female parts mature before the male ones. (See how the stamens haven't yet split to release their pollen.)  Protogyny is a mechanism to reduce self-pollination.

Luzula flower cluster
Woodrush (Luzula) flower cluster. May 1, 2009. Hocking County, Ohio.

Meanwhile, along a nearby roadside farfaraway, coltsfoot plants have advanced to the fruiting stage and we see why, not looking carefully, you might mistake them for dandelions. Even the fluffy heads look different though. They're equally fluffy, but fluffy in a different way.

coltsfoot and dandelion
Two fruiting weeds in the Aster family. May 1, 2009. Hocking County, Ohio.
Left: dandelion (Taraxacum officinale). Right: coltsfoot (Tussilago farfara).

Fluffy in a different way? Yes. Dandelion/coltsfoot "fluff" is the pappus --the highly modified calyx (sepals) of members of thr Asteraceae. In both these genera the pappus is composed of numerous hairlike ("capillary") bristles that facilitate wind dispersal of the single-seeded fruits. Hoever, the Taraxacum (dandelion) pappus bristles are fused into a single stalk that extends from the apex of the single-seeded fruit and at its tip spreads into separate bristles, whereas the pappus of Tussilago (coltsfoot) bristles are simple and separate for their entire length.

dandedion head of achenescoltsfoot head of achenes
Fruiting heads of two asteraceous weeds.
Left: dandelion. Right: coltsfoot.

Now that the coltsfoot leaves have emerged and expanded, we see the basis for its metaphorical name.

coltsfoot leaves
Coltsfoot leaves suggestive of equine hoofprints. May 1, 2009. Hocking County, Ohio.

American sycamore --the eastern sequoia!
Columbus, Ohio
April 30-May 7, 2009

American sycamore (Platanus occidentalis, family Platanaceae) can be thought of as our "sequoia" --an ancient and superlative tree, huge, distinctive, spectacular, and well-loved. Among eastern trees, tuliptree (Liriodendron) is occassionally taller, but by combining exceptional girth and height, sycamore is our most massive tree. Pioneer families sometimes lived inside hollow ones whilst their cabins were being built. In Birds of America (1840) John James Audubon recounts how he hired someone to cut a hole through the base of one densely occupied by chimney swifts in Louisville, Kentucky so that he could inspect the nests. Audubon estimated that 9000 birds roosted in that single tree!

American sycamore is a forest giant that is also a beloved lawn and street tree. Incidentally, the modifier "American" is helpful with this tree because in Europe, "sycamore" refers to a species of maple (Acer pseudoplatanus), while the common name "plane-tree" is employed for old-world Platanus species.  An American sycamore in the Clintonville neighborhood of Columbus has branches conveniently situated to enable a close look at its flowers.

American sycamore
American sycamore, Columbus, Ohio. May 6, 2009.

The architecture of this specimen is interesting. A low branch extends 40 feet from the trunk and touches the ground, but just barely. It's actually free to move in a breeze.

low branch of sycamore
Low branch of American sycamore. Columbus, Ohio. May 6, 2009.

American sycamore is flowering now. The trees are monoecious and wind-pollinated, producing numerous tiny flowers all of one sex in dense globose clusters produced singly in the axils of leaves. The staminate heads, at least in this example, are much more numerous than the pistillate ones.

staminate sycamore heads
American sycamore staminate heads before (center of photo) and during/after (side heads)
dispensing pollen. April 30, 2009, Columbus, OHio.

Other than the pollen-producing anther portion of the stamens, all the parts of the individual male flowers are very small and difficult to distinguish. The pollen maturation and associated dispersal process is remarkable. Each stamen consists, as is typical, of a pair of pollen sacs located alongside one another. Here, the two pollen sacs are connected at the top by an expanded and centrally attached "peltate connective" that is contiguous with all the other flowers' peltate connectives, causing the the staminate heads to start out smooth, firm, and effectively sealed shut which the pollen inside the head is becoming mature. The anthers split longitudinally, and the pollen is finally released when the anthers fall from the inflorescence!

Here are studio shots of an immature staminate head. This one is fresh from the tree.

sycamore staminate head
American sycamore staminate head. May 7, 2009.

...and this is a cross-section. Note the expanded peltate connective lying atop each stamen, abutting the others to seal the ball shut while the extremely long narrow anthers split lengthwise, releasing copious amounts of pollen. There are said to be 3 to 7 minute sepals, and an equal number of tiny petals. Good luck finding them.

sycamore staminate head split
American sycamore staminate head. May 7, 2009.

The pollen is dispersed as the male heads fall apart. Here's one at the onset of that process.

sycamore staminate head dehiscing
Sycamore staminate head disarticulating. April 30, 2009. Columbus Ohio.

...and a closeup view, in the studio.

sycamore staminate head late stage
Sycamore mature staminate head. May 7, 2009.

Here's the best part. Dirty trees!!! The stamens are shed, and they rain onto streets and sidewalks.

sycamore stamens on the ground
Shed sycamore stamens litter the ground. April 30, 2009. Columbus Ohio.

On average, the much less numerous pistillate (female) heads have been in flower a bit longer than the male ones as the species is protogynous --the female flower parts develop before the male ones, a mechanism to reduce self-pollination.

sycamore pistillate flowers
Sycamore pistillate flower head. May 7, 2009. Columbus, Ohio.

...and here's a closeup view of a pistillate head in the studio. It's very stylish.

sycamore pistillate head closeup
Sycamore pistillate head. May 7, 2009.

The pistillate flowers are described as being apocarpous, consisting of separate 5 to 9 separate carpels. There are no petals. The 3 to 7 sepals are minute. There are said to be "staminodes" (reduced sterile stamens); these might be the fluffy-looking things mixed in with the carpels.

scamore pistillate flowers split
Sycamore pistillate flowers. May 7, 2009.

By the end of the summer the pistillate heads will have matured into the familiar ping-pong-ball sized aggregate of achenes that is the basis for several other common names of the plant: buttonwood tree, and button-ball tree.

More recent observations ("next")