Today's entry was written in the summertime by Alexis, but since I thought it more timely for the autumn, it's been saved until now. Alexis writes:

Courtnay Janiak (Seaweed Lady@Flickr) provides today's photo via the Botany Photo of the Day Flickr Pool. Thank you, Courtnay!

Celastrus orbiculatus, also known as oriental bittersweet or Asian bittersweet, is native to eastern Asia but was brought to North America for ornamental purposes in the 1860s. Today, it has become a problematic invasive species in eastern North American agricultural land, forests, grasslands, and coastlands. Though the species is partial to gap and edge habitats, it is able to establish in shaded forests and remain until the canopy opens. Once exposed to moderate sunshine, it can quickly grow and spread. Growing as a woody vine or trailing shrub, Asian bittersweet will smother other vegetation, obstructing photosynthesis or directly damaging the plants.

This species looks similar to and is often confused with North America's native bittersweet, Celastrus scandens. The two species can hybridize--a trait that, along with competition, threatens the survival of the native species.

Another entry written by Alexis from this past summer. Alexis writes:

Today we conclude the prehistoric plant series with a species from the Cretaceous period. This photo from Wikimedia Commons was taken by Scott Zona (scott.zona@Flickr); the original photo can be found on Flickr. Thanks, Scott!

Amborella trichopoda is generally accepted as the sole remaining representative of the most basal lineage of flowering plants. The divergence of the ancestors of this "sister" species from all other flowering plant lineages occurred approximately 130 million years ago.

The present-day distribution of the species is restricted to New Caledonia, where it grows in "moist, shaded understory of montane forests". Amborella trichopoda is a dioecious woody shrub pollinated by wind and insects that produces tiny flowers on both male and female individuals and small red fruits on the females only.

For additional reading, see this National Geographic article on the origin of angiosperms: "The Big Bloom--How Flowering Plants Changed the World".

Second-last in the prehistoric plant series written by Alexis:

Damon Tighe (Damon Tighe@Flickr) shares this photo from Lake Merritt, Oakland, California via the Botany Photo of the Day Flickr Pool. Thank you, Damon!

Also known as bunya pine, Araucaria bidwillii is part of a genus that dates back to the Jurassic period. In the Mesozoic era, species of Araucariaceae could be found in both hemispheres, "dominating the low latitudinal belt of summer-dry climates and living in mixed conifer communities in the middle latitudes" (Thomas and Spicer's The Evolution and Palaeobiology of Land Plants (1987)). Today, the range of the family is smaller, mostly restricted to the southern hemisphere. As one example, Araucaria bidwillii only occurs naturally in Queensland, Australia. In the fossil record, Araucaria bidwillii is present mainly in the form of seed cones (PDF).

In the wild, this species grows in rainforests on basaltic soils where it is often found with Araucaria cunninghamii.

A distinctive (and potentially dangerous, should you be under the tree) feature of Araucaria bidwillii is its female cones, which can be 30cm in length and weigh 10kg! For Aboriginals of Queensland, bunya seeds were a highly valued food source. The wood of this species is strong and straight-grained, and so is a desirable source of timber.

From a series assembled and written by Alexis over the summer:

The prehistoric plant series continues today, and we progress through the geologic time scale to the Triassic period. Much thanks to Keith Board for sharing his photo of Osmunda claytoniana, which was taken in a swamp forest at the Indiana Dunes State Park in Porter County, Indiana. Keith is a contributor at this neat blog, Get Your Botany On!.

Osmunda is a genus of about six terrestrial fern species. Osmunda species grow in open, wet environments such as bogs, swamps, and lake edges. The genus has a wide distribution throughout the globe, though it is limited by climates that are too cold or dry (Tryon & Tryon's Ferns and Allied Plants (1982)).

Osmunda claytoniana has the "oldest known fossil record of any living fern", and can be traced back to the Triassic period. This species can also be considered a living fossil, because it appears almost identical to a fossil fern species from 200 million years ago, Osmunda claytoniites. It has gained the common name interrupted fern because of the appearance of its fronds, on which the brown fertile pinnae "interrupt" the green sterile pinnae.

Alexis continues with the series on ancient plants she assembled during the summer:

Mats Ellting (melting@Flickr) took this photo of a Ginkgo biloba leaf in Eskilstuna, Sweden, and shared it through the Botany Photo of the Day Flickr Pool. Thanks, Mats!

Currently, Ginkgo biloba is the only known existing species of Ginkgoaceae. The term living fossil is often used to describe Ginkgo biloba since it appears the same today as it did in the past, as seen in the fossil record. This species dates back to about 190 million years ago, but the order to which it belongs, Ginkgoales, can be traced back earlier, to the Permian period. In the mountains of China, the species survived in Buddhist monasteries and were introduced throughout Asia around 1100 AD. It did not reach Europe or America until the 1700s. During the Cretaceous, at least five or six other Ginkgo species existed. Our knowledge of these now-extinct species is based mainly on leaf remains, since the stems and fruits rarely survive the fossilization process (Tidwell's Common Fossil Plants of Western North America (1975)). Leaf shape also helps to distinguish different species from one another. For example, the leaf of Ginkgo dissecta has a deeply dissected blade, as the species name implies, creating several lobes.

Ginkgo biloba is a dioecious tree species native only to China, though it is cultivated around the world and has been used for many medicinal treatments. Listed as Endangered on the IUCN Red List, the only surviving wild population is reportedly found on Tianmu Mountain, in the Zhejiang province of China.

Alexis writes:

We continue the prehistoric plant series with this fossil (noted to be about 22cm long), showing the branches and thin leaves of Lepidodendron lycopodioides. Thank you to the user Woudloper at Wikimedia Commons for the photo.

Lepidodendron species were a dominant plant species in the Carboniferous period, and lasted until the late Permian. Also called scale trees or giant club mosses, they used spores to reproduce and were tree-like in habit, growing over 30m tall with branches splitting in twos (an illustrated reconstruction). However, support for their large bodies came not from their wood, which only existed as a thin strand in the centre of the trunk, but from their thick bark. On their branches and trunks, Lepidodendron species had distinctive diamond-shaped scales called leaf cushions that denoted where leaves used to be (Andrews' Studies in Paleobotany (1961)); these unique patterns are often seen as fossil impressions.

The arborescent lycopsids are known to have grown in peat swamps. Most of the coal deposits found in the eastern US and western Europe today originated from the bark of arborescent lycopsids. Different lycopsid genera are classified by the shapes of leaf cushions and position of vascular strands. Their closest living relatives appear to be the diminutive clubmosses and quillworts, groups of fern allies incomparable to the stature of Lepidodendron.

Alexis continues with the prehistoric plant series she assembled in the summer:

Thank you to Forest & Kim Starr for sharing their photos from Maui, Hawaii via Wikimedia Commons (photo 1 | photo 2). Psilotum nudum grows in subtropical and tropical conditions and can be epiphytic.

Plants of the Psilotales, such as the pictured Psilotum nudum, are recognized as the most primitive plants currently living. Psilotum species are known as whisk ferns and though they do not appear in the fossil record, they share characteristics with extinct flora like Cooksonia.

The Rhynie Chert in Scotland is a sedimentary rock formation that contains a variety of fossilized plants and animals from the Early Devonian period, about 400-412 million years ago. It contains very well-preserved specimens of early vascular plants like Aglaophyton, which, like today's Psilotum, had no true leaves or roots, possessed rhizomes and sporangia, and a dichotomous branching pattern. Additionally, there is evidence that Aglaophyton species were myco-heterotrophic, having a symbiotic relationship with arbuscular mycorrhizal fungi that helped the plant to absorb nutrients; fungi often associate with present-day members of the Psilotales in the same way. Because of their similarities to Devonian flora, whisk ferns are uniquely significant for research purposes.

From a prehistoric plant series that Alexis assembled over the summer:

Today's first photo shows a fossilized specimen (about 2.5cm tall) of Cooksonia pertoni from Shropshire, England, dating from the Upper Silurian. Much thanks to Hans Steur for permitting us to share his work!

The second photo shows a model of Cooksonia found in the Evolution House at the Royal Botanic Gardens, Kew. Thanks to Drew (Drew Avery@Flickr) for sharing the photo! Along with fossils, these models can help us imagine what Earth's early plant life may have looked like.

In 1937, British botanist William Henry Lang was the first to describe the extinct genus Cooksonia, based on specimens he found in Wales. From his findings, he identified two species: Cooksonia pertoni and Cooksonia hemisphaerica. Since then, more fossils of the genus dating from the Silurian to Lower Devonian have been found in Europe, Africa, and North America (see: Thomas and Spicer's The Evolution of Palaeobiology of Land Plants (1987)). It should also be noted that Cooksonia is not considered to be an evolutionary clade (not all the species have a common ancestor), but rather it is a grade, a group in which species share similar morphology.

Cooksonia is often credited with being the "first vascular land plant." Despite its reputation, however, it is uncertain whether all Cooksonia species were vascular. Some fossilized impressions show evidence of vascular tissue in the form of a dark strand in the centre of the plant's axis, but not all Cooksonia specimens do. What is certain is that Cooksonia was a small plant, no larger than 15cm tall, possessing several distinctive features such as a dichotomous branching pattern, lack of true leaves, and sporangia found on the tips of the branches, that are now associated with other early land plants.

For this week and some of next, we'll have some entries that Alexis put together over the summer.

Alexis writes:

Today's photo is from Wikimedia Commons (also on Flickr) and was taken by Ruth Ellison at Lake Thetis, Australia. Thanks, Ruth!

Today, we start a photo series of prehistoric plants, spanning the Cambrian period to the Cretaceous period, some extant, some long extinct, and some with living relatives.

Dating back to the Early Archaean about 3 billion years ago, stromatolites are evidence of the earliest known photosynthesizing organisms, cyanobacteria. Though cyanobacteria are also known as blue-green algae, they are not related to true algae, which are in the domain Eukaryota and not Bacteria. Modern living stromatolites can be found today in aquatic environments such as Shark Bay, Australia.

Stromatolites are made of alternating layers of cyanobacteria and sediment, and can vary in shape from mounds to pillars. To create these unique formations, the bacteria first weave around sediments to form thin mats. The ideal environment for stromatolite formation is water shallow enough to allow sufficient sunlight for photosynthesis. These can include marine environments, intertidal zones, and lakes like British Columbia's Pavilion Lake, which is the focus of much research. As more sediment gets stuck to the mats, the cyanobacteria are forced to spread vertically to maintain their access to sunlight. Sediment continues to stick to the organisms and the process continues, building layer on layer, forming a stromatolite.

In the fossil record, stromatolites are identified in cross-section by their curved laminae (via this page on stromatolites). These fossilized sediment layers (the organic bacterial mats having been long decomposed) are the only evidence that remain of the ancient cyanobacteria that we have to thank in part for generating an oxygenated atmosphere.

Returning once again to South America this week, with an entry that Alexis wrote this past summer. As an aside, I've hired a new work-study student thanks to your donations (which directly support these hires). I'll introduce her when her first entry is ready to be posted.

Alexis writes:

Dave Winkel shares this photo from Chile's Torres del Paine National Park. Thanks, Dave! Calceolaria uniflora, also known as Calceolaria darwinii, is native only to Argentina and Chile.

A study of plants of this species in southern Patagonia suggests the existence of two subspecies of Calceolaria uniflora that differ in two flower features: the appearance of the instep (in the photo, the splotchy lower lip), and the colour of the throat (the somewhat striated middle portion). The instep displayed two phenotypes within the study area. A uniformly dark red instep was called uniform and a patchier instep with more yellow and orange was called maculate. Throat colour varied from dark red to orange to yellow, though no discrete colour categories could be established.

The study found that instep type correlated with the geographical longitudinal position of the flower populations; more specifically, populations in the western forest and grassland were uniform, populations in the eastern steppe were maculate, and intermediate areas had mixed populations with individuals of both types. The throat colour variable, however, showed a latitudinal pattern, with individuals becoming more orange and less yellow from north to south.

The authors suggest several explanations for these morphological variations within the species. It is possible that different species of pollinators (such as Thinocorus rumicivorus) are attracted to different flower types, and that these variations are an adaptation designed to attract the appropriate pollinators, though there is no evidence yet to support this hypothesis. Different climatic conditions could also play a role; the study observed that flowers tended to be redder in the south, containing more anthocyanin, a feature that may help shield the plant against the cold weather and UV radiation prevalent in that region. Additionally, geographic barriers, isolation, and gene flow could have all contributed in developing the two observed subspecies of Calceolaria uniflora, and further studies may present more evidence.

Today is Alexis's last day working on Botany Photo of the Day, though she's assembled a number of entries I'll be using in the upcoming weeks. Alexis writes:

Drew Avery (Drew Avery@Flickr) took these photos (image 1 | image 2) in the Copenhagen Botanical Garden in Denmark. Thank you, Drew!

Echinops sphaerocephalus, growing 50-200cm tall, belongs to the largest family of vascular plants, Asteraceae. A single inflorescence (3-6cm in diameter) is comprised of many tiny florets, each "surrounded by spiny involucral bracts" (Polunin's Flowers of Europe (1969)). The species is native to Asia and Europe, but is also cultivated elsewhere. It typically blooms from June to September in the northern hemisphere.

The genus name comes from the Greek echinos, meaning "hedgehog", and opis, meaning "appearance", likely referring to the inflorescence or the bristly leaves, which have spiny margins. Sphaerocephalus is also derived from Greek and means "sphere- or round-headed". The species is probably better known as great globe thistle or pale globe thistle. Echinops sphaerocephalus usually occurs in rocky, dry areas and disturbed sites.

Alexis authored today's entry:

Today's photo of a young rhubarb plant is via Wikimedia Commons and was taken by Andrew aka polandeze@Flickr (original Flickr page). Thanks, Andrew!

The use of rhubarb can be traced back as early as 2700 BC in China, when the dried roots of Rheum officinale and Rheum palmatum were used as a laxative. The species Rheum rhabarbarum, native to Mongolia and surrounding regions, was first cultivated in England in 1573. Though initially cultivated for its medicinal properties, by the eighteenth century it had been subject to (additional?) hybridization, and the hybrid's leaf stalks became a desirable food. All parts of the plant contain oxalic acid, and the leaves themselves are poisonous to people and animals if ingested in large amounts.

There are many cultivars of rhubarb, differing from each other by properties such as colour, size, and acidity level. Phillips & Rix's Vegetables (1993) served as a valuable reference for this entry.

Today's entry was authored by Alexis:

Thank you to Tony Foster (Tonyfoster@Flickr) from the Botany Photo of the Day Flickr Pool (image) and Kahuroa at Wikimedia Commons (image) for their photographs of today's species. Cordyline australis produces sweet-scented white flowers that bloom in October to December in the southern hemisphere. The flowers attract flies, which carry out pollination.

This species, also known as cabbage tree, is endemic to New Zealand. It is a common tree in New Zealand, found in a variety of habitats like "swamps, sand dunes, coastal scrub and forest margins, river banks and dry hillsides" (Newhook's Our Trees: A New Zealand Guide (1982)). It grows up to about 20m tall. Parts of the tree can be eaten and are rich in carbohydrates. Historically, Maoris made a porridge-type food out of the sun-dried pith and roots of young trees, and also used the trees as sources of fibre and medicine. Early European settlers found uses for Cordyline australis as well; they fashioned chimneys from the hollowed out trunks, which are fire-resistant, and made beer from the roots.

In 1987, Cordyline australis individuals of the North Island of New Zealand fell victim to a mysterious disease that caused sudden wilting, the falling off of leaves, and death within 3 to 12 months. This condition, simply known as "sudden decline", was later discovered to be caused by a phytoplasma parasite transmitted via an introduced sap-sucking insect.

An entry written by Alexis today:

Thank you to forum member davallia for posting these photographs of Aechmea gamosepala on the BPotD Submissions Forum. These were taken at the Royal Botanic Gardens in Melbourne, Australia.

Aechmea is a genus in the Bromeliaceae that has over 200 species. Its name derives from the Greek word aichme, meaning "spear".

The common name for this Brazil native is matchstick plant, and its flowers do resemble its namesake. Bromeliads are known for their showy bracts, and in the case of Aechmea gamosepala, they are pink in colour, while the petals are purple. Though the flowers are relatively short-lived, they bloom several times annually, making it a desirable ornamental. Typical of Bromeliaceae, the leaves are arranged in a rosette. Aechmea gamosepala grows to about 30cm in height, and can be epiphytic (sometimes growing on trees).

Alexis authored today's entry:

Van Swearingen (Van in LA@Flickr) took these pictures at the Los Angeles County Arboretum and shared them in the Botany Photo of the Day Flickr Pool (photo 1 | photo 2 | photo 3). Thanks, Van!

Ceiba insignis, sometimes still called by the synonym Chorisia insignis, is a deciduous tree native to the dry forests of western South America. Commonly, it is known as the white floss-silk tree, chorry, or white dragon. Oftentimes, the tree fattens significantly towards the base, a fact that likely caused the species to garner the nickname South American bottle tree. The sharp prickles seen on the trunk can become over an inch wide as the tree grows and its trunk widens. When young, the bark is green but as the tree ages it turns grey. When fruits (from Trees of Miami) reach maturity, they split open to reveal seeds that are surrounded by silky white hairs. These have been used as a stuffing for pillows and life vests.

This species is quite similar to Ceiba speciosa, and they may be difficult to differentiate when not in flower. Usually, Ceiba insignis has white flowers with golden throats and Ceiba speciosa's flowers are pink with white throats. However, variation does occur and sometimes Ceiba speciosa may produce paler flowers or Ceiba insignis may have slightly pink flowers (ref: Krishen's Trees of Delhi (2006)).

Today's entry was written by Alexis.

Scott Zona (aka scott.zona@Flickr) took this photograph at the Wertheim Conservatory & Greenhouse at Miami's Florida International University. Thank you for sharing, Scott!

Stapelia flavopurpurea is a small succulent species native to South Africa and Namibia, usually found growing beneath bushes and in stony areas. It is associated with calcrete.

Stapeliads are also known as carrion flowers because they often give off unpleasant odours (often like rotting flesh) that attract flies, which act as pollinators. Stapelia flavopurpurea is one of the few Stapelia species that do not have a stinky smell. On the contrary, they may give off a pleasant scent; the scent of the lighter-coloured flowers has been compared to that of honey or marzipan. The flowers of this species are also highly variable in appearance and exhibit an array of colours. The flower lobes can vary from brown to red, green or yellow. The centre of the flower is typically white, but covered in hairs that may be white or purple. Lastly, the corona is white to red-purple with a yellow-tinged base (ref: Bruyns' Stapeliads of Southern Africa and Madagascar (2005).

Thank you to BlueRidgeKitties@Flickr for sharing these two photos (photo 1 | photo 2) via the Flickr Pool. These images of Bazzania trilobata were made near Linville Falls in North Carolina.

Liverworts can be broadly separated into two distinct artificial groups: leafy and thalloid. Bazzania trilobata is an example of a leafy liverwort. Though they look like mosses and have a similar life cycle, leafy liverworts have important morphological differences that set them apart. For example, liverwort leaves are often in two lateral ranks with a third row of smaller leaves on the back of the stem, while moss leaves have a spiral arrangement (Vitt et al's Mosses, Lichens & Ferns of Northwest North America (1988)).

Bazzania trilobata grows in "large clumps or dense widespread mats on boggy soils, forest ground, rotten logs, and at the bases of trees especially in cedar swamps and hemlock or boreal forests". It is difficult to track down a precise distribution for the species, but it has been observed in northern temperate forests at a minimum. Generally, Bazzania species are more typical of tropical environments, though they grow in a wide range of climatic conditions, only excluding deserts and the poles (Schofield's Field Guide to Liverwort Genera of Pacific Northwest America (2002)).

The leaf orientation of Bazzania trilobata is worth noting, as it is the opposite of most liverworts. As seen in the close-up photo, the upper edges of this species' leaves overlap the lower edges of the leaves above them. This is described as an incubous leaf arrangement. The majority of leafy liverworts have the opposite arrangement, succubous, where the lower edges of the leaves overlap the upper edges of the leaves below them.

Today's entry was written by Alexis:

From the Botany Photo of the Day Flickr Pool, Doug (shyzaboy@Flickr) shares this photograph of Morinda citrifolia taken in Puerto Plata, Dominican Republic. Thanks, Doug!

Morinda citrifolia is now fairly widely distributed around the world and goes by many names in different countries; it is often called noni, a Hawaiian term, and its English names include rotten cheesefruit, Indian mulberry, and canary wood. Though the species originated in southeast Asia and Australia, it is now naturalized in tropical regions of the Pacific, North America, and South America. Evidently, Morinda citrifolia (PDF) has been known to successfully establish after spreading to new areas, giving it the potential to become invasive. A unique trait the seeds have is the ability to stay viable for several months while in water--a useful skill when dispersing across oceans or rivers. However, the species is not currently considered a major threat.

Morinda citrifolia grows as a shrub or small tree, blooming in the summer and autumn. From a cluster of its flowers comes a single compound fruit or syncarp; the still-developing fruit in the photograph can be expected to turn yellow-white and grow to 5 to 10 cm in length. If you're looking for a possible natural remedy for ailments such as headaches, high blood pressure and muscle pains or if you just need some Vitamin C, the juice of the fruit can be drunk and is sold commercially. The species has also been investigated for prevention of cancer.

Today's entry was written by Alexis:

Anne Elliott (annkelliott@Flickr) shares this photo via the Botany Photo of the Day Flickr Pool and writes, "The nodding/musk thistle is my favourite kind of thistle, especially at this stage, when the pinky purple flower has died and the beautiful pattern of the spiny bracts can be seen more clearly. Flower head is 4-6 cm in diameter. Photographed at the Erlton/Roxboro Natural Area on July 27th, when I called in for a short walk after my afternoon volunteer shift. There were a lot more of these plants this year, so I guess this invasive weed really does spread". Thank you, Anne!

The name nodding thistle refers to the plant's large flower head, which is often seen bobbing up and down. Wikimedia Commons has a picture of the flower in full bloom.

Carduus nutans occurs naturally in western Asia and across Europe. In North America, however, the species is a major weed, especially in farmlands. It out-competes native plant species, creating dense colonies that livestock refuse to walk through and cannot eat because of the spines. As an invasive species, the musk thistle has an advantage since it lacks natural predators and can spread its seed quite quickly.

In the United States, biological methods of pest control have been implemented in addition to chemical and mechanical approaches. Two species of weevils from Europe, Rhinocyllus conicus and Trichosirocalus horridus, have been introduced to some areas affected by Carduus thistle invasions; the former target the plant's developing seeds, while the latter eat the root crowns. Yet, as with many pest control methods, this one is not without risk, as the introduced insects may also affect non-target species. In Wisconsin, for example, the weevils are not used due to the associated threat to rare thistles native to the state.

Alexis wrote today's entry:

The series of plants endemic to the Hawaiian Islands concludes today with Erythrina sandwicensis. These photographs (photo 1 | photo 2) were taken by Forest and Kim Starr, and accessed through Wikimedia Commons.

This tree occurs on leeward slopes on all eight major Hawaiian Islands, as they prefer hot, dry, rocky environments. The species also grows on old lava fields, dry canyons and gorges. Wiliwili loses its leaves in late summer or autumn, and flowers bloom in early spring or summer, so leaves and flowers are rarely seen together. Though the flowers are commonly orange, colour polymorphism exists within the species and white, yellow, peach, red or light green flowers also occur. Additionally, the presence of lichens tends to give the wiliwili trunks an orange tinge (Pratt's A Pocket Guide to Hawaii's Trees and Shrubs (2006)).

Erythrina sandwicensis is known for possessing among the lightest wood of all Hawaiian trees. For this reason, native Hawaiians found it was a useful material for surfboards and outriggers for fishing canoes (Rock's The Indigenous Trees of the Hawaiian Islands (1974)). This species is the only member of Erythrina native to Hawaii. Its Hawaiian name wiliwili, meaning "repeatedly twisted", refers to the seedpods that twist to reveal their red seeds. These are commonly strung together to make leis.