Series Longipetalae (Diels) Lawrence

Series Longipetalae (Diels) Lawrence A group of plants within the section Limniris from Western North America with persistent fruiting stems (into 2nd year) a 2-toothed stigma, and capsules with six ribs and tapering at both ends; Diels in Engl. & Prantl, Nat. Pflanzenfam. Aufl. (1930); G.H.M. Lawrence in ‘A reclassification of the genus Iris' in Gentes Herbarium 8:346 (1953), New York. Noted as Longip. in registrations. Generally it is agreed that there are two species, (BIS Species guide only recognizes I. missouriensis) but the varieties and forms seem confused.
Iris longipetala Herbert
Iris missouriensis Nuttall

A third species is listed here but it is unclear where it should be placed.
Iris pariensis Welsh

References:

Dykes in The Genus Iris, 1913; As the longipetala group;
XIII. The Longipetala group.

In this group, which probably comprises two species and one subspecies, there has been considerable confusion. I. longipetala comes from the Pacific coast, and has a sturdy stem and a many flowered spathe. It is largely evergreen in winter, probably in its native home and certainly in England, owing to its habit of throwing up new leaves in the autumn. This Iris is never found apparently at any great distance from the Pacific, but there is a mountain or upland form, which differs only from I. longipetala in its more slender growth and shorter leaves, which moreover do not begin to grow until the spring. Nuttall's specimen (BM) leaves no doubt that it was to this plant that he gave the name of I. missouriensis. The flowers are practically identical with those of I. longipetala, though perhaps somewhat more slender. Both plants, however, possess the short yellowish-green perianth tube which springs fronr- the ovary with hardly any perceptible constriction. It was to this same upland form of I. longipetala, for it can hardly be looked upon as a distinct species, that Herbert gave the name of I. tolmeiana. His type-specimens still exist in the British Museum, and I have no doubt that this name is merely a synonym of I. missouriensis. Confusion has arisen because this plant has also been described and figured under the name of I. longipetala montana. The name was taken presumably from a sheet of specimens from Nuttall in the British Museum labelled montana, though Nuttall probably never published the name. His plants, however, are quite distinct from I. missouriensis. They have the relatively shorter stem, the pointed and not obtuse, emarginate standards, and the slightly longer, narrower and darker perianth tube possessed by the Iris figured at Plate XXII. For this species it seems best to retain Nuttall's name montana, because the name has already been applied for some time to one member of the group. Nuttall undoubtedly saw the difference between I. missouriensis and I. montana, and we owe it to him to retain his names.

As garden plants, I. missouriensis and I. montana are quite easily separated, but in dealing with herbarium specimens it is often impossible to say with confidence to which species we must assign them. If {he tips of the standards are visible, it is easy to separate them, for I. montana has pointed standards differing at a glance from the blunt, emarginate tips of the standards of I. missouriensis. The latter has usually more flowers than two in the spathe, and the pedicels are longer, while I. montana only rarely produces a third flower.

The habitats of I. missouriensis and I. montana are, roughly speaking, west and east of the Rocky Mountains, but a careful study of available specimens seems to show that, though in the north the dividing)lne follows the watershed through Montana, Wyoming and Colorado, there is in New Mexico an extension of I. missouriensis in a south-easterly direction, which cuts off some colonies of I. montana in Arizona-particularly in the neighbourhood of Flagstaff-from the main body in Eastern Colorado and Wyoming. I have it on the authority of Dr N. L. Britton, the Director of the New York Botanical Garden, that such south-easterly extensions of the habitats of plants belonging to the flora of the Great Basin are not uncommon, and I have therefore less hesitation in giving I. montana specific rank. Its characters are constant under cultivation and in successive generations. It must be confessed, however, that with herbarium specimens alone it is impossible to work out the exact distribution of these two species. I have tried to identify as many specimens as possible, but I am not always confident that the identification is correct.

The cultivation of the members of this group is easy. They appear to succeed in almost any soil, but do best, perhaps, in a rather heavy loam. This may, however, be merely due to the fact that in such a soil a plant does not soon exhaust the stock of food within reach of its roots, and for some reason or other all these species do best when left undisturbed to form large masses. In a light soil two or three years of luxurious growth impoverishes the soil to such an extent that, unless liberal top-dressing in autumn and winter is carried out, the plants begin to fail and become less floriferous.

Some very good garden hybrids of I. montana crossed with pollen of I. longipetala were raised by Foster, ,and are now in commerce under the name of Tollong, I. tolmeiana being the name by which Foster knew I. montana.

The three plants that form the group may be separated as follows:-

Plant sturdy, spathes many flowered, pedicels long, standards blunt emarginate, mature leaves as long as or longer than the stem................I. longipetala

Plant slender, spathes many flowered, pedicels long, standards blunt emarginate, mature leaves shorter than the stem.................I. missouriensis

Spathes usually only two-flowered, pedicels short, standards oblanceolate pointed, mature leaves longer than the stem...............I. montana

 

-- Main.RPries - 2010-02-18
Topic revision: r3 - 28 Nov 2016, BobPries
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