Imágenes de páginas

from hour to hour. .... The filaments have merely spread out, not grown, by means of their peculiar movements. These movements are of three kinds; first, there is the oscillating movement, one end of the thread remaining nearly at rest, while the other sways from side to side, sometimes describing nearly a quarter of a circle in a single swing. Secondly, the tip of the filament has a minute movement, bending from side to side, like the head of a worm; and thirdly, there is an onward movement, probably the result of the two former. It is this latter which causes the filaments to radiate, and spread out from the edges of the stratum."

But we must refer the curious reader to the work itself, which, though framed on a systematic and strictly scientific basis, is yet replete with physiological matters of general interest. We could have wished for a detailed account of the recent discoveries, by Pringsheim and others, of the sexual fertilization of the spores of the lower Algæ, which takes place in a variety of wonderful ways. Reference, however, is made to the original memoirs, of which, indeed, some abstracts have been given in former volumes of this Journal.

The plates, although, from the nature of the subjects, not as showy as those of the second part, are handsome and admirable.

A. G. 2. Species Filicum ; being descriptions of all known Ferns. Nlustrated with plates ; by Sir William Jackson Hooker, K. H., &c. London : 1858. William Pamplin. Parts VII and VIII, or Vol. II, Parts III and IV. 8vo, pp. 250, tab. 111-140.—The publication of this work is resumed after an interval of six years. This delay, we are told, “ has been a source of great regret both to the author and to the publisher, and has been in a measure, occasioned by the great difficulty and labor of the subject in hand, -especially in a genus so extensive as that which occupies nearly the whole of the portion now issued, viz., Pteris.” Besides Pteris the author has here elaborated Llavea, Cryptogramme, Pellæa and Ceratopteris. Llavea consists of a single Mexican species separated from Pelloa by habit rather than by any characters of fructification. Cryptogramme is also considered as monotypic, C. crispus being made to include the East Indian C. Brunoniana, and the North American C. acrostichoides. The older name of Allosorus is rejected both for this genus and for Pellæa on account of the vagueness of its character, as originally drawn up by Bernhardi; Sporangia cathetogyrata, sessilia, sub-aggregata. Hyposporangia sub-communia, margine libero, sub-pellucida ;' and because it has been made a receptacle for Ferns of very varied structure, according to the different views of authors respecting the limits of the genera, especially of those included in this work under the name of Pellæa.” The genus Pellæa was proposed by Link in 1841, adopted by Fée, in his Genera Filicum, and here accepted by Sir William Hooker. It includes thirty-three species, of which one third are found in the United States, viz., P. gracilis in the Northern States; P. atropurpurea from Vermont to Texas; P. Bridgesii and P. densa in California; and P. cordata, P. flexuosa, P. andromedæfolia, P. pulchella, P. Wrightii, P. longimucronata and P. Orithnopus in the region between Texas and California. The last three species are probably but forms of one, which must bear the name of P. mucronata. [Vide Botany of Mexican Boun

dary Survey. Under the genus Pteris the author remarks: “It will be seen from the characters and the references given, that I have taken the bold step, and what many will consider a retrograde movement in botany, in restoring almost entire the original Pteris of Linnæus and Swartz and Willdenow." Reviewing at some length the various modern genera, Campteria, Litobrochia, Doryopteris, Heterophlebium, etc., into which various authors have divided the Linnæan Pteris, he concludes with the opinion that “as new light is continually being thrown upon this family of plants, it is premature to sanction the great multiplication of genera by laying stress on the nature of the venation when unaccompanied by any corresponding changes in fructification, or any marked differences in habit, and more philosophical to consider such groups in the light of sections or subgenera. The importance of the vascular structure is acknowledged; an arrangement, to say the least, equally natural, is preserved, and some degree of stability is given to names invented and sanctioned by the most illustrious botanists that ever lived." This mode of regarding Pteris is perfectly in accordance with the way in which Lindsæa and Adiantum were treated in the earlier part of the work, and on the whole must recommend itself to the student of general descriptive botany. The investigator of a single natural order is peculiarly liable to commit the fault of excessive subdivision, while a botanist, like Sir William Hooker, eminent in all departments of his science, will naturally take wider, not to say sounder, views of the limits of genera and species. One hundred and twenty-three species of Pteris are admitted, not including a large number of obscure species, of which no notice is taken, and the fifteen or twenty nominal species, which are reduced to the cosmopolitan Pteris aquilina. Ceratopteris thalictroides, Brongn., after having been referred to five different suborders by various botanists, and by one even excluded from the family altogether, is here associated with Pteridece, not from any real similarity of structure and habit, but because no better place has been found for it. We may remark in passing, that it is not quite correct to say, as on page 155, that Agardh excluded only the Allosori of Bernhardi and Presl from the Linnæan Pteris, since in fact, he excluded all those that Swartz called “Adiantoideve ;” among them, P. pedata, the type of Mr. J. Smith's genus, Doryopteris. Pteris dispar, Kunze, in Bot. Zeit. 6, p. 539, is evidently the same plant as P. semipinnata, var. B, and should have been given as a synonyme of it. An advertisement affords the gratifying intelligence that the first part of the third volume may be expected at an early day.

D. C. E. 3. Catalogue of North American Birds, chiefly in the Museum of the Smithsonian Institution, by SPENCER F. BAIRD, Assistant Secretary of the Smithsonian Institution.—This Catalogue by Prof. Baird, enumerates 738 species of birds, of which all but 22 are strictly North American. All the 738 were determined from specimens, excepting 31. Wilson's work in 1814 contained 283 species, Bonaparte's in 1838, 471 species, and Audubon's in 1844, 506 species. The catalogue therefore contains nearly one-half more species than Audubon enumerated. The Catalogue is especially valuable as a list of well ascertained localities, thereby indicating the range of the species. The author's habitual care and untiring zeal in research authorize full reliance on its accuracy.

4. Odontology, by Prof. Owen.—A very extended article of great value on Teeth, very fully illustrated, is published by Prof. Owen, of London, in the 16th volume of the Encyclopedia Britannica (8th edition). It takes up the whole range of vertebrates and includes both fossil and recent species among its illustrations. The wood-cuts, of which there are near 200, are excellent and highly instructive.

IV. ASTRONOMY. Donati's Comet, or the Great Comet of 1858.-In our last number we were favored by Prof. Wm. C. Bond, of the Observatory of Harvard College, with a brief notice of this splendid Comet. In Runkle's Mathematical Monthly, Nos. 2 and 3, (Cambridge, Mass. Nov. and Dec. 1858,) Mr. Geo. P. Bond, of the same Observatory, has published a highly interesting and valuable account of this body. Rarely has so fine an opportunity been presented for observing the physical constitution and internal changes of a comet, and the opportunity has been well improved. The second part of Mr. Bond's paper occupies 26 pages and is enriched by numerous wood-cuts, and by two engraved telescopic views of extraordinary beauty. We cite a few passages from this important memoir, and hope that our readers will procure and read the full account.

“The interest of the telescopic view, taking all the circumstances into account, the size of the instrument, the perfect purity of the atmosphere, and the splendor of the object, have rarely been surpassed. The nucleus and the outline of its nearest envelope were visible in full sunshine with the large telescope. The head of the Comet could be seen with the naked eye at twenty minutes after sunset, at which time the second envelope was discernible with the telescope. It is most remarkable, that, with all this accession of brightness, the nucleus itself had now diminished to a diameter of only four or five hundred miles, scarcely one fifth of what it was on the morning of the 9th of September, by a very careful determination. Its volume had thus diminished to one-twentieth part only. The remaining nineteen-twentieths had, in the intervening period, expanded into the tail, or had gone to form the envelopes which now encircled it, by a process which has been fully illustrated in the preceding pages. But are we then to conclude that the nucleus, in the focus of these mysterious operations, had in this way expended the greater part of its substance? To this inquiry the best reply is a consideration of its subsequent condition. After several more eruptions from its surface, similar to those above described, it receded from our view about the 20th of October, with an evident increase of size compared with its condition two weeks before, and still shining with its accustomed intensity."

“ Examined in the day time on the 5th with the highest powers which it would bear, no indication of a phase could be seen. * * "

“The tenth of October was the day of nearest approach to the earth, but the comet was manifestly on the wane, though expanded over a larger extent of the sky than before. Five envelopes, reckoning the exterior haze as one, could be traced through the whole or some part of their outline."

“ We must add a few words on the appearance presented by the tail between the 6th and the 10th of October. At the date first named, one of the supplementary rays, attained a distance of 55° or fifty millions of miles from the nucleus, somewhat exceeding that of the principal tail, and in a direction as usual, nearly in a line from the sun. Others less perfectly developed could be discerned near a point where the curvature of the main stream was pretty suddenly changed. On the 8th five or six transverse bands could be distinguished in the tail half a degree or less in breadth, with clear, well-defined outlines, and perfectly resembling auroral streamers, excepting that they kept their position permanently, that is, without motion sensible to the eye, they diverged from a point between the sun and the nucleus."

“ The train attained its largest apparent dimensions on the 10th, when the main stream of light could be distinguished through an arc of 60°, corresponding to a length of fifty-one millions of miles, or rather more than half the distance of our earth from the sun. The distribution of its light at a distance of 20° or 30° from the nucleus in parallel or slightly diverging bands, alternating with dark spaces, was strongly exhibited. They were 5° long, and 20' or 30' wide, and might aptly be compared either to the streamers which often break up the continuity of an auroral arch, or to a collection of five or six tails of small comets, forming from the remains of the large one."

“The most recent intelligence leaves no room to doubt that the comet of Donati is periodical, having a time of revolution of about two thousand years. The following are the results arrived at by different computers :

Watson, - - - - - - 2415 years.
Bruhns, - - - - - - 2102 "
Löwy, - - - - - - 2495
Graham, - - - - - - 1620 “
Brünnow, - - - - - - 2470 “

Newcomb, - - - - - - 1854 " “Supposing its last perihelion passage to have occurred at the beginning of the Christian era, it must have passed its aphelion in the early part of the tenth century, at a distance of 14300 millions of miles from the sun, its velocity at that point being 480 miles an hour.”

V. MISCELLANEOUS SCIENTIFIC INTELLIGENCE. 1. Tables, Meteorological and Physical, prepared for the Smithsonian Institution ; by Arnold Guyot, LL.D. 2d edition, revised and enlarged. Washington, Smithsonian Inst., 1858, 8vo.—The full value of this extensive and important collection of tables it is impossible to exhibit without a detailed catalogue, which our limits do not permit. They are selected from a wide range of authorities, by a gentleman who is well known for his thorough acquaintance with the best sources of knowledge on these subjects, and for his faithful and exact computations. The amount of labor demanded for the preparation of the work must have been great, and the scientific men of all countries are under weighty obligations to the accomplished editor, and to the Secretary of the Smithsonian Institution for making accessible at so cheap a rate, so precious a collection of auxiliary tables.

A first edition of part of these tables appeared in 1852. More than three times as much matter is contained in the present volume, as in the former issue. The work now comprises six series of tables, viz.: I. Thermometrical,

15 tables, in 35 pages. II. Hygrometrical,

33 “ “ 165 III. Barometrical,

28 " “ 134 " IV. Hypsometrical,

26 and 44 “ 149 " V. Meteorological Corrections, 99 tables“ 120 € VI. Miscellaneous,

6 " " 12 The following remarks are made by Prof. Guyot in respect to the construction of these tables :

“ In the Thermometrical series six small tables have been added; they were prepared for converting into each other differential results given in degrees of any one of the three thermometrical scales, irrespective of their zero point.

“The Hygrometrical series has been entirely reorganized. It only contained five tables, all in French measures, and the appendix. It is now composed of twenty-seven, arranged in three divisions. In the first are found ten tables, based on Regnault's hygrometrical constants, both in the psychrometer, the dew-point instruments, and for computing the weight of vapor in the air. The whole set in English measures, and Table V in French measures, have been prepared for this edition. Being based on the best elements we now possess, they are given here for ordinary use. The second division contains the seven most important tables published in the Greenwich observations, and Glaisher's extensive Psychrometrical Table. These tables being much used in England, and the results obtained by them exhibiting no inconsiderable differences from those derived from the preceding ones, they are indispensable for comparing the results. The third division, composed of ten miscellaneous tables, furnishes the means of comparing the different values of the force and the weight of vapor, especially those which have frequently been used in Germany, and also of reducing the indications of Saussure's Hair Hy. grometer, to the ordinary scale of moisture. The appendix remains as in the first edition, but all the tables have been revised and corrected.

“ The barometrical series now in four divisions, has been increased from twelve to twenty-eight tables. Excepting three small tables for capillary action, all the new ones bave been computed for this edition. The comparison, now so much needed, of the Russian barometer with the other scales, appears here for the first time.

“The Hypsometrical series is almost entirely new. It contained only Delcros's table for barometric and Regnault's table for thermometric measurements, besides two auxiliary tables and the thirteen small tables of the appendix. It now offers twenty-three tables for barometrical measurement of heights, in which all the principal formulas and scales are represented; three for the measurement of heights by the thermometer, in Freuch and in English measures; and a rich appendix of fortyfour tables, more extensive and convenient than those in the old set, which afford the means of readily converting into each other all the measures usually employed for indicating altitudes.

« AnteriorContinuar »