ENGKLMANN — OAKS OF THE UNITED STATES. 395 



pubescent scales, the acorns mostly ovoid-globose, retu<:o, or oval and 

 pointed. I have, with some hesitation, followed DeCandolle and Gray in 

 uniting with this species ^. tinctoria^ Bart., which has longer and more 

 pointed buds ; broader, less lobed and firmer leaves, paler on the under 

 side, smaller and more pointed acorns, at least in the few fruiting speci- 

 mens I have been able to examine, and a deep yellow-colored inner bark. 

 I suspect that specific differences may yet be discovered ; for the present I 

 venture to introduce it as a subspecies. 



^. Georgiana, M. A. Curtis, confined, as far as known, to that isolated 

 granite rock, the Stone Mountain, east of Atlanta in Georgia, which is also 

 the onlv locality for Gymnoloma (formerly Rudbeckia) Porteri, Gray, ^nd 

 tor Isoi-tes melanospora.* Leaves glabrous from the first, generally lance- 

 oval, oval or sometimes obovate, mostly coarsely sinuate-toothed, with 2-4 

 teeth or lobes, rarely pinnatifid or sometimes entire or undulate; crowded 

 acorns small, subglobose ; shallow, flat cups, truncate or rarely rounded at 

 base, with triangular, obtuse, nearly glabrous, appressed scales. Perhaps 

 too near ^. palttslris, from which the fruit is scarcely distinguishable, 

 though the locality, the growth and the foliage differ. 



^. laurifolia, Michx., appears after all to be distinct from ^. aquatica ; 

 whether entire or lobed, the leaves of the latter mostly have a cuneate out- 

 line widest in the upper third or at least above the middle; the calyx lobes 

 are larger and very conspicuous, and the filaments enclosed and only the 

 anthers exsert. ^. laurifolia has lanceolate oblong leaves, widest about 

 the middle whether entire or lobed ; the calyx lobes are much small- 

 er; filaments exsert; this in flowering specimens of both species from 

 Bluff'ton, the only ones which I could compare. A specimen from the 

 gulf coast of Mississippi has oval entire coriaceous leaves 4 inches long 

 and li inches wide, while those of the South Carolina plants are narrower, 

 and rather approach to Pkellos, but never to aquatica. They usually per- 

 sist until the budding time, but not beyond it. 



^. cinerea, Michx. In specimens from South Carolina I find, together 

 with the ordinary stellate pubescence, an abundance of yellow articulated 



* fsoetes OT^/a«o.'/6>ra. n.sp. amphibia, parvula, gregaria. plerumque monoica; trunco 

 placentiformi bilobo; foliis paucis (5-io) distichis stomatosis sine fasciculis fibrosis peri- 

 phericis ; velo sporangium suborbiculare totum tegente ; macrosporiis (0.3S-O.4S mm- 

 diam.) minutissime sub lente verruculosis obscuris (humidis nigricantibus), microsporiis 

 (0.028-0.031 mm. longis) papillosis obscuris. 



In shallow depressions a. couple of inches deep and a few feet in diameter, on the naked 

 granite surface near the top of the mountain, where occasional rains and dews furnish tem- 

 porary and precarious moisture, but where for weeks and even months the glaring sun, 

 flashing on the naked rock, parches and bakes them : discovered by Wm. M. Canby in 

 May, 1869; revisited by Prof. Gray in April, iSyj. and by Mr. Canby and myself in Septem- 

 ber, 1S76, when nothing was perceptible but ihe dead, matted root-fibres attached to the 

 small shrivelled corms. — Corm 3-4 lines in diameter, flat, only y^-i \\m thick; leaves 2-3>i 

 inches long, in all the specimens examined distichous, which I have not seen in any other 

 species; sporangia ^-% line in diameter, usuallyeniarginateabove, almost black from their 

 dark contents, but without any brown cells ; often nmaining for a time attached by their 

 base when their leaf has withered away. The plant, which I have cultivated for several 

 vears, seems to vegetate as soon as moisture is furnished, but lies dormant part of the year;^ 

 spores mature in May and June. — This species. /. jlaccida from Florida, :ind /. Nuttallii 

 from Oregon, are tlie only American Isoetes in which the spore case is entirely enclosed in 

 and covered by the velum; and it is the only one of ours with dark spores, all the others 

 having white ones. 



