Sunday, November 23, 2008

Euonymus occidentalis















At the first pass I had no idea what this was - opposite arrangement so immediately, the options narrowed. The first individual I came across was not in fruit so based upon the leaves and buds I thought "A small Cornus nuttallii? No." Buds were dead wrong and no parallel veination. Then when I came across an individual in fruit there was no doubt: the rare Euonymus occidentalis (western wahoo/burning bush) - Celastraceae. A great place to see this species is Lewis and Clark State Park near Mary's Corner, WA - it's all along the main hiking trail that spurs off the interpretive trail. Not common enough to merit a photograph in Pojar - it's listed under Pachistima myrsinites (Oregon box) also in the Celastraceae family.













The inflorescence of the western wahoo are greenish-purplish to purplish-red (I've yet to see this in reallife - but in photographs, similar in color to the bloom of Asarum caudatum) - Hitchcock describes the flowers as "mostly 3-flowered axillary cymes". What is the fruit all about? - pictured above, with seeds covered by a reddish-orange aril (in Hitchcock - "fruit a 4-5-celled leathery capsule, seeds arillate"), Pojar describes the fruit to be similar in construction to a cashew. I was careful not to disturb the individuals I found - but if any readers have information on how this fruit is put together - I would love to hear about it. This species is of "threatened" conservation status and the ones I came across, I let be.

How about some more terms:
aril = an appendage growing at or near the hilum of a seed; fleshy thickening of the seed coat, as in Taxus.
hilum = a scar on a seed indicating its point of attachment (How great to have a term for this!)
cyme = a flat-topped or round-topped determinate inflorescence, paniculate, in which the terminal flower blooms first.
determinate = describes an inflorescence in which the terminal flower blooms first, halting further elongation of the main axis (all Harris and Harris).