wise than an idle whim. With many of the prairie sunflowers, however, the facts are different; especially is this so in the case of H. rigidus. Morning after morning, at flowering time, the heads of this species may be seen bending gently towards the east; they are erect at mid-day, and at evening gracefully droop towards the west. This continues day after day for weeks, with surprising regularity and uniformity. Later, however, the stems grow rigid and remain nearly vertical. In this case at least the popular notion referred to above seems well founded.

Aside from the open prairie species already mentionedwhich embrace the greater part of the most conspicuous ones -numerous others of almost equal interest are found growing in the low grounds, and in the open forest belts that skirt the streams. Prominent among these are coreopses and sunflowers of several species, especially the C. aristosa and C. tripteris, Helianthus strumosus, H. decapetalus and H. tracheliifolius; the ground nut (Apios tuberosa Mœnch.) with its fragrant, dark purple flowers; the western iron weed (Vernonia fasciculata Michx.), the great St. John's-wort (Hypericum pyramidatum Ait.), the broad-leaved polygonum (P. Pensylvanicum Linn.), and, in more open and drier places, the rag-weeds (Ambrosia), the wormwoods (Artemisia), the tick-trefoils (Desmodium), the bush clovers (Lespedeza), and the psoraleas. Many species of such eastern plants as love rich moist woods, are also found here.

One of the strangest features, perhaps, in the flora of the prairies, and that which of course constitutes them prairies, is the entire absence of arboreal or even suffruticose species, the timber of this region, as is well known, forming open park-like belts along the streams, which with great propriety have received the name of "groves." Here the species, as might be expected, more strongly recall the flora of the East, the resemblance extending not only to the trees and shrubs, but to the herbaceous species that flourish beneath their shelter. But the predominant species can hardly be regarded

as properly eastern forms, while the entire absence of representatives of some large groups of trees and shrubs that are common at the East makes the difference greater than at first seems. One may traverse hundreds of square miles in the prairie districts without meeting a single birch, alder, a chestnut, beech, or aspen (Populus tremuloides Michx.), nor any species of pine, spruce, hemlock or other coniferous tree, all of which are so abundant in the forests of the Atlantic States as to constitute the prevailing species. Two species of cottonwood (Populus monilifera Ait., and P. angulata Ait.), so closely allied as to be confounded as one by the casual observer, but neither of them exclusively western, are probably the most characteristic trees, as they are certainly the most abundant and important. The sugar maple, the linden, elms, bitter-nut and other hickories (chiefly the former), butternuts, black walnuts, burr, white, black and other oaks, several species of ashes, the beautiful ash-leaved maple (Negundo aceroides Manch.) and the locust (Robinia Pseudacacia Linn.), are the principal and almost the only important kinds of timber, the greater number of which are more or less common trees. Among the shrubs are several species of sumach (Rhus) and the hazel bush (Corylus Americana Walt.), which here, as at the East, principally compose the thickets, whilst the Ceanothus, or Jersey tea, is a frequent inhabitant of the prairies. One searches in vain, however, for any whortle-berry bushes (Vaccinium), of which so many species abound at the East, or for any representatives of the large family Ericaceae, than which no family is more characteristic of the woodlands of the Eastern States. Viburnums are common, and the elder (Sambucus Canadensis Linn.), the honeysuckle (Lonicera), the snowberry (Symphoricarpus), and other caprifoliaceous shrubs are more or less frequent. The wild apple, the Washington thorn (Crataegus cordata Ait.), and the wild plum are common among the rosaceous shrubs, but blackberries and raspberries are rare. The wild plum grows in the river

bottoms in unsurpassed perfection. Though they are all, or nearly all, of the same species (Prunus Americana Marsh), the varieties in respect to the form, size, color and quality of the fruit are almost endless, the plums varying in form from spherical to egg-shaped, and from nearly white through every intermediate stage of color to yellow and even dark red, and in flavor from bitter, uneatable kinds to those as delicious as the highly cultivated varieties of the garden.

From the abundance of woody climbers the forests of the river bottoms sometimes present an almost tropical aspect. The Virginia creeper (Ampelopsis quinquefolia Michx.), and the winter grape (Vitis cordifolia Michx.), climb to the tops of the highest trees, with a diameter of the stem exceeding any specimens I have elsewhere seen. Other climbers are frequent, including the singular wild cucumber, or balsam apple (Echinocystis lobata T. & G.), which assumes an almost tropical luxuriance, here and there abundantly enveloping the trees.

The restriction of the forests to the river bottoms and their banks has previously been alluded to as a remarkable feature, of which various explanations have been offered. The fact of the rapid encroachment of the forests upon the prairies wherever they have been protected from exposure to the annual fires that formerly swept over the country, and the rapid growth of the timber whenever it becomes established, indicate clearly that not only have the fires had much to do with their restriction, but that there is nothing either in the climate or the soil unfavorable to their rapid spread. The damper northern slopes of the streams being also generally better wooded than the necessarily drier southern slopes, also points to the fires as the great agency that has operated through long ages to check their increase, and that their circumscription has had little to do with the peculiar origin of the prairies and of their present flora, as some have formerly supposed.

As has been already incidentally remarked, the vegetation

of the open prairies, as compared with the herbaceous vegetation of regions to the eastward similarly situated geographically, is mostly made up of coarse, large species, and of forms peculiar to the prairies. It consists, moreover, principally of a comparatively few predominant forms,-features strongly in contrast with those of the neighboring regions. The grasses, like the exogenous species, are also few in species, but coarse and luxuriant, as they are the product of a soil of unsurpassed fertility. Yet the flora as a whole is one singularly susceptible to the inroads of civilization. Even the grazing of cattle for a few years is sufficient to materially alter its character. The grasses, according to the testimony of early settlers, soon dwindle in size and luxuriance, while the relative abundance of the other plants becomes materially altered. As already remarked, the breaking and turning of the soil at once exterminates a large number of the previously dominant species, and instead of lingering as troublesome weeds, the more hardy exotics, that through man's influence assume an almost cosmopolitan habitat, usurp their places, the cereals, the cultivated grasses and the noxious weeds of the old world thoroughly crowding out the original occupants of the soil. With all the beauty and the novelty of the primal flora of the prairies, the traveller, after a few weeks of constant wandering amid their wilds, is apt soon to experience a monotony that becomes wearisome, the full degree of which he scarcely realizes till the soft green sward and the varied vegetation of cultivated districts again meet his eye.

DISTRIBUTION OF THE MARINE SHELLS OF FLORIDA.*

BY DR. WILLIAM STIMPSON.

ONE of the most striking peculiarities of the zoology of Florida is the diversity in the character of the littoral shells of the two sides of the peninsula. The naturalist passing from St. Augustine to Cedar Keys finds upon the western beach a group of shells so different from those he had seen upon the Atlantic shore, that he is reminded of the similar (though vastly greater) difference in the fauna which exists on the two sides of the continent itself; for instance, at the isthmus of Panama. This diversity is seen in the common large shells as well as in the fauna taken as a whole. Thus on the cast coast Busycon canaliculatum, B. carica, Dosinia discus, Arca incongrua and A. Americana are the most abundant shells, while they are not found at all on the west coast; and at Cedar Keys and Tampa Bay we find the subtropical species Cassidulus corona, Busycon perversum, Pyrula papyratia, Strombus alatus, Bulla occidentalis, Callista gigantea, Dosinia elegans and Arca Floridana? strewed on the beaches in great numbers, while they occur but rarely on the east coast; some of them not at all. The list presented contains the names of three hundred and fourteen species collected by me on the two coasts, of which only one hundred and forty-five, or less than half, were common to both; fifty-eight being peculiar to the east and one hundred and eleven to the west coast. Several of these species are indeed representative, but specifically quite distinct. These results will no doubt be considerably modified by future researches, as some of the smaller species may have escaped detection on one or the other of the two shores, although really existing upon both. But the fact will, nevertheless, remain that a marked difference exists between the fauna of these shores notwithstanding their proximity and notwith

* Abstract of a paper read at a recent meeting of the Chicago Academy of Sciences.