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.

standing the comparatively recent origin of the peninsula which separates them.

Of the recent origin of the Floridan peninsula (or at least of the northern part which makes the separation between the great Carolinian Bay and the Gulf of Mexico), we have not only geological but zoological evidence. Although, as shown above, the littoral fauna* of that part of the gulf which bathes the west coast of Florida is of a character far more tropical than that of the east coast, the fauna of the latter is reproduced in the northwestern part of the gulf. The correspondence between the shells of Galveston and those of South Carolina was noticed by Roemer many years ago, and the fact is now confirmed by an examination of the shells brought by Dr. Durham from several points on the coast between Point Isabel and Pensacola. The peninsula and warm waters of the southern cape of Florida now form an impassable barrier to the western migration of species of the temperate fauna into the colder parts of the gulf, but of their connection within a comparatively recent geological period there can be no doubt. The connection was probably through sandy straits and lagoons, too shallow to allow of the passage of the gulf-stream, but perhaps permitting the westward flow of the cold waters of the Carolinian Bay.

The present tropical character of the shells of the west coast of Florida is plainly due to the influence of the gulfstream, which is not here, as in the northwestern part of the gulf, crowded off the shores by the waters of a great river, or by cold northwest winds. On the other hand the east coast, as far south as Cape Canaveral, forms a part of the shore of the Carolinian Bay, along which, inside of the guif-stream, a cold current runs, giving to this part of Florida a coast fauna similar to that of South Carolina.

*By the littoral fauna, that of the true ocean shores is here meant. The waters of the shallow inlets and estuaries of the west coast are subject to great changes of temperature, which, during the winter "northers," may fall to the freezing point, at which times fish caught in such places die in great numbers. As might be expected, the fauna of these inlets is very different from that of the beaches, and such northern forms as Modiola plicatula and Cardium Mortoni, which are adapted to such extremes of temperature, find here a congenial station.

THE BORERS OF CERTAIN SHADE TREES.

BY A. S. PACKARD, JR.

In no way can the good taste and public spirit of our citi zens be better shown than in the planting of shade trees. Regarded simply from a commercial point of view one cannot make a more paying investment than setting out an oak, elm, or maple or other shade tree about his premises. To a second generation it becomes a precious heirloom, and the planter is duly held in remembrance for those finer qualities of heart and head, and the wise forethought which prompted a deed simple and natural, but a deed too often undone. What an increased value does a fine avenue of shade trees give to real estate in a city? And in the country the single stately elm rising gracefully and benignantly over the wayside cottage, year after year like a guardian angel sending down its blessings of shade, moisture and coolness in times of drought, and shelter from the pitiless storm, recalls the tenderest associations of generations after generations that go from the old homestead.

Occasionally the tree, or a number of them, sicken and die, or linger out a miserable existence, and we naturally after failing to ascribe the cause to bad soil, want of moisture or adverse atmospheric agencies, conclude that the tree is infested with insects, especially if the bark in certain places seems diseased. Often the disease is in streets lighted by gas, attributed to the leakage of the gas. Such a case has come up during the past year at Morristown, New Jersey. An elm was killed by the Elm borer, Compsidea tridentata of Olivier, and the owner was on the point of suing the Gas Company for the loss of the tree from the supposed leakage of a gas pipe. While the matter was in dispute, Mr. W. C. Baker of that city took the pains to peel off a piece of the bark and found, as he writes me,