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Oct 16, 2014: Sinowilsonia henryi

Sinowilsonia henryi

Martin Deasy's series on the Hamamelidaceae continues today with its fourth entry. The fifth, and final entry, will appear on Saturday. Martin writes:

The monotypic genus Sinowilsonia is named for the prolific English plant hunter E. H. "Chinese" Wilson, immortalizing both his surname and his nickname (the prefix "sino-" means "pertaining to China"). The species was first collected for Western science from the wild in 1889 by the remarkable Irish plantsman Augustine Henry, and bears his name. The original herbarium voucher specimen he sent to Kew can be viewed digitally (or see Wilson's 1907 collection of the same species).

Sinowilsonia henryi is a medium-sized tree native to the mixed forests of central China. Its unisexual inflorescences--effectively a type of catkin--are numerous and highly distinctive. Both male and female catkins are ca. 5cm long at pollination, but the rachis of the female inflorescence elongates markedly after fertilization, attaining a final length of 20cm or more.

The photograph shows a fertilized female inflorescence in the process of elongating. Each flower bears twin pinkish-green styles and 5 greenish sepals on a swelling pistil. Sporadic rusty-brown stellate trichomes (a familiar Hamamelidaceae character) are also visible on close inspection. Adjacent are the exhausted male catkins, beginning to dessicate having released their pollen some time earlier.

Sinowilsonia's reduced flowers (lacking petals and either male or female sexual parts) are typical of wind-pollinated taxa, which do not require petals to attract pollinators, but instead need to produce large volumes of pollen to maximize the chances of fertilization.

The characteristic inflorescences of Sinowilsonia (together with those of the other anemophilous Hamamelidaceae genera Sycopsis, Distylium and Parrotia) give some insight into why the Hamamelidaceae were historically closely aligned with other families of wind-pollinated catkin-bearers (the artificial grouping dubbed the Amentiferae). Systems such as that of Engler & Prantl treated them as neighbours to e.g. Fagaceae, Betulaceae, Juglandaceae, Urticaceae and Platanaceae, and despite almost immediate dissent, these relationships proved surprisingly slow to be dismantled.

More sophisticated morphological, and later molecular, taxonomy made clear that the reduced flowers found in wind-pollinated catkins were highly derived--that is, they did not represent a "primitive" ancestral state, and were therefore of little use in drawing conclusions about evolutionary relationships between taxa. Fragments of the Amentiferae are now widely scattered within the Fagales, Rosales and even Proteales. The Hamamelidaceae, meanwhile, are located firmly within order Saxifragales (the apically unfused bicarpellate pistils, and twin styles, are highly diagnostic).

In fact, within the Hamamelidaceae alone, wind pollination has evolved several times, in each case from an ancestral state of insect pollination. Thus most of Hamamelidaceae's anemophilous genera are found within tribe Fothergilleae, whereas Sinowilsonia has evolved separately within tribe Eustigmateae.

Oct 16, 2012: Larix lyallii

Today's write-up and photographs of Larix lyallii are courtesy of Bryant, BPotD work-study student. He writes:

These subalpine (or alpine) larches were photographed on the northeast face of Mount Frosty in British Columbia's E.C. Manning Provincial Park. Larix lyallii is one of my personal favorites for its unusual characteristics and its ability to survive higher altitudes and harsher conditions than most other conifers. Larix is one of the few genera of deciduous conifers (other deciduous conifers). In early/mid-September through early/mid-October in British Columbia, this species changes colour from green to a stunning golden-yellow. Larix lyallii grows in upper montane zones that would otherwise be considered alpine tundra (usually above the treeline of evergreen conifers), as well as on exposed rock outcrops. Its native range follows high alpine environments in southern (primarily southeast) British Columbia, southwestern Alberta and northern Washington, Idaho and Montana (distribution map).

Although trees of Larix lyallii are stunted by the long and harsh winters they endure, their trunks typically remain straight and upright (compared to displaying characteristics of Krummholz formation often seen among subalpine evergreen conifers). This is largely due to the deciduous characteristic, which helps to reduce the effects of winter desiccation and snow loading. The extreme hardiness of this species has helped it to become one of the longer lived species of conifer, with the known record holder being an individual 1,917 years old in Kananaskis, Alberta as of 2012!

Morphologically, Larix lyallii can grow up to 31m tall with a diameter at breast height of 215cm. As one might expect, larger specimens are generally found at lower elevations. The needles are quadrangular and grow in bunches of 30-40 atop abaxially keeled short shoots. They tend to grow in moist immature/rocky soil that is well drained. Plants grow at elevations between 1,900 and 2,380 metres, with slightly lower elevations in the North Cascades (1,830 to 2290m). Larix lyallii may also grow in association with Pinus albicaulis (whitebark pine), Abies lasiocarpa (subalpine fir), and Picea engelmannii (Englemann spruce) at the upper limits of their elevational distributions.

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