Art. XVIII.—On Danthonia nuda Hook. f. and Triodia Thomsoni (Buchanan) Petrie, comb. nov.

By D. Petrie, M.A., Ph.D.

[Read before the Auckland Institute, 28th November, 1911.

In my herbarium there is a good specimen of Danthonia nuda Hook. f., collected at a high elevation on the Ruahine Range, Hawke's Bay. There can be little doubt that this plant is a true Danthonia, though it makes some approach to the genus Triodia. Sir J. D. Hooker's description of it is brief, and wanting in some important details. The culms are very slender, leafy, and but little longer than the leaves. The sheath of the topmost cauline leaf is three or four times as long as the blade, which reaches to the base of the panicle. The flowering-glumes show considerable variation in the hairy covering, which is more ample than one would suppose from Hooker's description. Besides the one or two small tufts of hairs on the sides of these glumes, there is usually a scanty band of sparse hairs across the back just above the middle, and often also a few straggling hairs lower down but above the basal tuft. The awn, which is quite straight, is one-third as long as the glume. The florets in each spikelet are more commonly 2 than 3.

I have a few indifferent pieces of what is most likely this species from the Tararua Range, collected by that excellent observer Mr. B. C. Aston. Unfortunately, they are all past flower.

Danthonia nuda has long been confounded, and by myself in the first instance, with a somewhat similar grass, the Danthonia Thomsoni of Buchanan. The latter was discovered by me at Mount St. Bathan's, Central Otago. As it has a wide distribution in districts explored by Hector and Buchanan, and also by Von Haast, it is singular that it was not found before. It may have spread and increased since these early explorations were made, but I consider it much more likely that it was merely overlooked or mistaken for some other species that was collected then. At present it has a wide distribution in the upland districts of South Canterbury, Otago, and Southland. It is fully and accurately described in Mr. Cheeseman's Manual under the name Danthonia nuda Hook. f, though he notes that his plant may not be the same as Hooker's. The grass is not, however, a Danthonia, but a characteristic species of Triodia, to which I now give the name Triodia Thomsoni. It was originally named in compliment to Mr. G. M. Thomson, and I am specially pleased to be able to associate permanently with it the name of this old and valued friend. As a pasture-grass Triodia Thomsoni possesses a high value. It has a fair amount of foliage, is deeply rooted so as to withstand drought and exposure to drying winds, and is palatable and highly nutritious. It forms one of the most common and useful of the bottom grasses of the tussock-steppe in all the upland districts through which it ranges, and is much eaten by sheep. It is well worth artificial cultivation, and promises to help in reclaiming the now desert and semi-desert lands from which the native pasture has disappeared through long-continued overstocking.

Triodia Thomsoni differs from Danthonia nuda in the narrow panicle with erect branches, the longer less-leafy culms that greatly exceed the leaves, the longer narrower more numerous spikelets that usually contain 5–7 nearly glabrous florets, and the much shorter less rigid awns.