1929, Iris Verna

Addisonia page 15, plate 456, 1929

IRIS VERNA (MOUNTAIN FORM)

Mountain Violet-iris

Native of the higher altitudes of the southeastern United States

Family Iridaceae, Iris Family

Iris verna L. Sp. pi. 34, 1753.

In most treatments of the genus Iris, the violet-iris, Iris verna, is indicated to have a range from the Coastal Plain to the mountains, with many herbarium specimens as evidence. That the plants from the two extremes of the range differ, has not been called attention to before; but the difference is so marked as to warrant the mountain plant as a distinct species but for the connecting forms occurring on the intermediate Piedmont region. Dr. Edgar T. Wherry, who has studied this plant in the field in some detail suggests the following to have been its geological history: During the several ice advances of the Glacial Period the southern Alleghenies no doubt had a considerably cooler climate than at present, and were largely occupied by plants of northern types. The finding of fossils of the tamarack (Larix laricina (DuRoi) Koch) in deposits of this age in Georgia, nearly five degrees of latitude south of its present southern-most native colony, brings this out clearly. Temperate climate plants were, however, able to survive on the Piedmont, and when the climate became warmer at the time of interglacial stages, so that the northern species largely died out, seeds from these piedmont refuges no doubt soon found their way into the higher altitudes, and started colonies in the unoccupied territory. Compared with the present-day members of this group in the mid-Piedmont, the mountain forms are decidedly denser in habit, with shorter and thicker rootstocks, and larger flowers sometimes quite lacking in odor. As the representative of this group which had occupied the Coastal Plain during the Tertiary showed opposite tendencies in these respects, the sum-total of the differences between them is considerable, and were not exact intermediates well developed in their ancestral Piedmont home, the two might well be classed as separate species. As it is, however, they seem best regarded as only geographical forms, as shown in the nomenclature proposed here.

The known range of the mountain violet-iris extends from South Carolina to West Virginia, usually at relatively high elevations, although it seems to mingle with the Piedmont form to some extent toward the inner edge of that province. The painting here reproduced was made from a plant collected on Panther Mountain, West Virginia, by Per Axel Rydberg in 1925. In its native haunts this iris is associated with small shrubs of the Heath and related families, especially Epigaea and Galax, in soils of rather high acidity and usually in open woodland. It begins to bloom in late April and often continues through the month of May, especially at the higher altitudes.

In the mountain violet-iris, the rootstock is torulose or alternately swollen and constricted, the nodes between the leaf -scars permanently close together, i. e., the internodes do not elongate and the roots are, borne freely along the entire length of the rootstock. The leaves are ten to fifteen inches tall, coral-pink at the base, with the color sometimes extending three to three and a half inches above the base, and colorless along the hyaline edges of the sheathing portion, persistent on the rootstock for three to five inches back from the growing tip; when finally they rot away, a raised light-brown ring remains on the rootstock : the blades are one third to one half an inch wide at maturity. The bases of the spent leaves are persistent on the rootstocks in brown tufts. The involucre is sessile, of usually seven to nine bracts, the outer two, three, or four scale-like, yellowish, the inner ones broad, successively longer, acute or slightly acuminate, and the two inner hooked at the apex, bright-green. The flower is erect, four to five inches tall, manifestly pedicelled, violet-scented. The hypanthium surrounding the ovary is slender spindle-shaped, three-angled, the angles and the faces with obscure median grooves. The free extended part (flower- tube) is stoutish, yellowish-green, with purplish stripes extending down from the base of the petals, between twice and thrice the length of the ovary, about equalling the involucre. The three sepals are one and three-quarters to two inches long, spatulate-cuneate, not distinguished into claw and blade, often abruptly acute, with a minutely papillose orange crest spotted with brown, and extending two thirds from the base, usually with flecks of white and lines of violet and brownish yellow between the crest and the violet margin and tip which is obscurely veined with deeper violet. The three petals are about as long as the sepals, broadly spatulate, with a very slender channeled claw which is pale- violet, becoming reddish-violet towards the base and an obovate deep- violet, abruptly acute blade. The three stamens are about three-quarters of an inch long. The style-appendages are half-ovate, nearly a half inch long, coarsely erose-lacerate. The stigma is entire. The capsule is oval or ellipsoid, varying to ovoid or obovoid, three-quarters of an inch to an inch and a quarter long, beaked, glabrous, long-stipitate, three-lobed, the lobes and the faces with slender ridges. The seeds are several in each capsule-cavity, the body is oval, about an eighth of an inch long, dark-brown, the aril is lateral and terminal, nearly or quite as long as the body, white or nearly so.

John K. Small

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-- BobPries - 2014-12-10