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auroral light gives the characteristic green line spectrum ; or, in other words, that spectroscopically dealt with, the slit being fine, the zodiacal light gives a background on which the faint auroral line (if aurora is present) may show itself as perfectly as though there were no zodiacal light at all. Hence Prof. Smyth's observation not only demonstrate the real nature of the zodiacal spectrum, but shows how the mistake of those arose who have supposed the zodiacal spectrum to be identical with that of the aurora.
Proper Motions of the Stars.—Dr. Huggins has been able to continue his researches into the proper motions of the stars in the direction of the line of sight. It will be remembered that the telescope he formerly used did not possess sufficient light-gathering power to deal with any star except Sirius. The instrument Dr. Huggins is now using has a light-gathering power four times as great. The first fruits of its employment in this line of research confirm in a very interesting manner the anticipations as well as the theories of Mr. Proctor. Dr. Huggins finds that certain stars are moring as if in systems or families, since they possess a common motion either of recess or approach. Among such instances may be mentioned one of a very remarkable kind. It may be remembered that Mr. Proctor, nearly three years ago, announced that the five stars 3, 7, 1, ?, and 5 Ursx Majoris, as well as Alcor close by %, and the telescopic companion of %, are moving in a common direction; and at a lecture delivered in May, 1870, at the Royal Institution, Mr. Proctor expressed his conviction that whenever Dr. Huggins applied the spectroscopic method to these stars, he would find that they are either all receding or all approaching. Many, unaware of the evidence on which this conviction was based, considered so definite a prediction altogether unwise. It has, however, been amply confirmed by the event, since Dr. Huggins finds these five stars to be all receding at the rate of about thirty miles per second. On the other hand the star %, which Mr. Proctor had indicated as not belonging to the set, is found to have a spectrum differing in character from that common to the five stars, and though receding, has a different rate. The star , also as marked by Mr. Proctor distinct from the rest, is found to have a totally different spectrum, and to be approaching. Thus the prediction referred to has been more than fulfilled; it has been found not merely that all the stars of the set are receding at the same rate, but that other stars excluded from the set are not moving in the same way, and are furthermore distinguished by spectral differences from the members of the drifting-star family.
Planets for the Quarter.—Saturn is the planet best placed for observation during the approaching quarter. He comes to apposition on July 9, at 11 h. 13 m. Jupiter will be in conjunction with the Sun on August 3, 4 h. 5 m. p.m., and is unfavourably situated for observation throughout the quarter. None of the other planets (except Mercury) will be well placed during the quarter. Mercury will be at his greatest eastern elongation on August 3rd, and at his greatest westerly elongation September 15.
August Meteors.—We remind our readers to look out for the famous August meteors on the nights of August 9, 10, and 11.
BOTANY AND VEGETABLE PHYSIOLOGY. Dispersion of Seeds by the Ilind. -A good parer on this subject has been contributed by M. A. Kerner, Director of the Botanic Garden of Innsbruck, to the “ Zeit. des Deutsch. Alpen-vereins." He made a thorough inquiry into the flora of the glacier moraines, and the seeds found on the surface of the glaciers themselves, believing that these must indicate accurately the species whose seeds are dispersed by the agency of the wind. Of the former description he was able to identify, on five different moraines, 124 species of plants; and a careful examination of the substances gathered from the surface of the glacier showed seeds belonging to thirty-six species which could be recognised with certainty. The two lists agreed entirely in general character, and to a considerable extent, also specifically ; belonging, with scarcely an exception, to plants found on the declivities and in the mountain valleys in the immediate vicinity of the glacier; scarcely in a single instance even to inhabitants of the more southern Alps. M. Kerner's conclusion is, that the distance to which seeds can be carried by the wind, eren when provided with special apparatus for floating in the air, has generally been greatly over-estimated ; and this is very much in accordance with the view advanced by Mr. Bentham in his anniversary address to the Linnæan Society of London in 1869. Along with the seeds M. Kerner found, on the surface of the glacier, more or less perfect remains of a number of insects belonging to the orders Lepidoptera, Hymenoptera, Diptera and Coleoptera, which, like the seeds, belonged almost exclusively to species abounding in the immediate neighbourhood of the glaciers.
The Fertilization of Conifere has been very carefully studied lately by Signor Delpino, who is now Professor in the State Forest School at Vallombrosa. He has been paying much attention to dichogamous flowers, and to the difference between those fertilised by the wind (anemophilous), or by insects (entomophilous), or by animals of whatever sort-zodiophilous, as he terms them. Coniferæ, as is well known, are avemophilous, that is, their fecundation is entrusted to the wind; their light and most abundant pollen is correlated to this, and the structure of the fertile inflorescence is such that the pollen reaches the very orifice of the ovule. In yew and cypress, and in other, if not all other genera of the sub-orders they represent, Delpino finds that, at the time when the ovule is ready for fecundation, a minute clear drop of liquid appears at the orifice of the ovule ; grains of pollen falling upon this are retained, are incited by it to develop the pollen-tube into the liquid first, thence into the ovule, and the drop is then re-absorbed or dries up. Alph. de Candolle, in a recent number of the “ Arch, des Sciences de la Bibl. universelle,” calls attention to the fact that this droplet was known, as to its appearance, function, and re-absorption, to his late venerable townsman, Vaucher, and is described in his “Physiology of the Plants of Europe,” published in 1841.
American Journal,” Nay, states that Maximowicz has collected in a Russian journal the observations and experiments on this subject, and recorded some observations of his own. He mutually crossed Lillium daruricum and L. writers, but are really characterised, according to Maximowicz, by the form of their capsules and bulb-scales. In the single experiment the pistil of Li bulbiferum fertilised by the pollen of L. davuricum, set fruit, but failed to mature it. That of L. davuricum, fertilised by the pollen of L. bulbiferum, matured well; but, to the surprise of the observer, it formed the long capsule of L. bulbiferum, instead of the short one of the species. This is an important experiment, but it requires repetition.
The Phenogamous Plants of the United States east of the Mississippi, and the l'ascular Cryptogamous Plants of North America north of Mexico.—This is the second edition, revised and corrected, and published now by Mr. B. Pickman Mann. It is, however, merely a reprint, with corrections and a few additions, of the catalogue known familiarly as “ Mann's Exchange List," which has been of great service to all collectors of American plants. Since the running numbers have not been changed, it will be possible to use the old and new editions interchangeably. The “ typographical and other errors," which have been found and corrected, are over 150, and Mr. Mann, in his preface, renews his brother's request that persons using the catalogue would send him notice of all errors discovered.
A Fungus-like Growth on the Leaves of Coleus Plants has been thoroughly investigated by Mr. H. J. Slack, F.G.S., who has read a paper upon the subject before the Royal Microscopical Society. In the first place, he says, a number of leaves were taken from coleus plants of various colours, and carefully examined in their natural state, both by transmitted and reflected light. It became apparent that every leaf, whatever its age or tint, exhibited chiefly, if not entirely on the under surfrce, a number of globular bodies of a beautiful yellow colour, highly translucent and refractive, most of them marked with a cross like that impressed upon the well-known crossbun. These bodies differed in hue from any yellow of the leaf, and they were distributed pretty uniformly without any regard to the variegations of the leaf-colouring matter. From damaged specimens, it was obvious that they were the bodies alluded to by Mr. Howse, who in a recent paper imagined them of fungous origin. The colour of these bodies, when looking healthy, and well filled with their refractive matter, varied from rich topaz to a pale sherry tint, and they glittered like jewels when well lit up. Empty cells had a rude resemblance to a mushroom in form, with a stout stem and a round head marked with the cross, but the texture did not look in the least fungoid, nor could any mycelium be discerned in or on the leaves.- Vide“ Monthly Microscopical Journal,” May.
Death of M. de Brebisson.—Those who are familiar with the large amount of work done by this gentleman will regret his death, which took place on April 26, in his seventy-fourth year.
Structure of the Dintomaceous Frustule.- Professor H. L. Smith gives his views on this subject in the April number of the “Lens.” Ile believes that all the frustules are “ siliceous boxes," with either one portion (the cover) slipping orer the other, as in Pinnularia, or with edges simply opposed, as in Fragilaria. If we take a frustule of Melosira, it may be coinpared to a pill-box-one portion slipping on to the other. The great majority of diatoms are thus constituted. It is perfectly evident that, in the case of the formation of a new valve, in the processes of self-division, this new
part, which slips out from the older, must be somewhat smaller. Inside of the box is a membrane, inclosing the internal coloured or colourless substance, imbedded in which may always be seen, at least in the larger forms, a distinct nucleus, sometimes two, and sometimes a "germinal dot," with numerous fine threads radiating from the nucleus, or the germinal dot. As the frustule increases in width, one portion slips out from the other, and sometimes successive additions of siliceous matter are made to the edges of the box, somewhat analogous to the successive additions to the edge of the shell of a mollusc. When the widening of the frustule has reached a certain extent, the lining membrane, at the places which would be exposed if the two portions were wholly to slip apart, infolds. He has reason to believe that, prerious to this, a double membrane of extreme tennity has been formed, commencing its growth at the nucleus (which itself is divided), and extended to the margins of the cell, which is thus divided into two nearly equal parts; for, as soon as this infolding commences (perhaps now accelerated by the admission of water), the line of division can be seen progressing steadily inwards by the parting of this thin double membrane, so that in fifteen or twenty minutes the fissure is complete. He has, in very large Pinnulariæ, witnessed the whole phenomenon, from its inception up to the final self-division. While the fissure occurs in the short period of time he has named, to complete the self-division requires about six days.
Is there Alternation of Generations in Fungi. Mr. M. C. Cook, M.A., belieres that it is questionable whether this phenomena occurs in fungi, as Professor (Ersted alleges. He thinks it takes place in the same plant, as in the case of Bunt; but he feels great difficulty in believing in this process, where the generations were passed in different plants, until confirmed by other observers. If the spores of Ecidium Berberidis were taken from the barberry and sown upon young wheat plants, and all these plants became infected with corn mildew (Puccinia graminis), to which wheat is but too prone, it certainly seemed premature to say that the spores of the Æcidium caused the Puccinia to be developed as a second generation; whereas it is much more probable that the germs of the mildew already lay dormant in the wheat, and, at most, the sowing and growing of the Æcidium spores only stimulated the mildew to a more rapid development.
Altering the Name of a Bog-moss.—Dr. Braithwaite is sufficiently conscientious in giving a new name to a species. In his last paper in the “Monthly Misroscopical Journal,” June, he gives the following observations on this subject. In Phänogamic Botany, Entomology, and other departments of natural history, the adoption of the first name by which a species has been described (dating from the establishment of the binomial nomenclature by Linnæus) is considered imperative; ret the synonymy of mosses is wofully confused, for Hedwig and others gare a new specific name as often as they changed the genus—a rule not sanctioned by the best authorities. Others may object with greater reason that the brief discriptions of the older authors are not sufficient to identify the species with certainty, yet it must be remembered that the actual specimens of very many of them are in existence, and their examination by a competent authority in most cases settles the question. Prof. Lindberg, who has worked so indefatigably at this unattractive department of botanical literature, has shown, in his “Rev. Crit. Ic. Musc. Fl. Dan.," that this species is in the St. Petersburg herbarium named tenellum in Ehrhart's own handwriting; this, however, without description, might not be allowed to stand, but the same species received the same name from Persoon, as proved by a specimen from him, preserved in Swartz's herbarium; and a description is giren by Bridel in his " Mantissa Musc.” (1819), the leares indeed being described as recurved at the point, which might perhaps refer to them in a dry state. Bridel also admits S. molluscum into the Bryol. Univ., but he only copied the description of Bruch (1825), without having seen a specimen. Dr. Braithwaite, therefore, has no hesitation in adopting the name first given to the species.
The Breathing Pores of Leaves.-A good popular paper on this subject is that which Prof. T. D. Biscoe read before the Troy Scientific Association, and published in the “American Naturalist,” March, 1872. If, he says, the outer layer or skin be stripped from the surface of the green-coloured parts of plants, and examined under a low power of the microscope, the stomata, or breathing pores, will appear as green specks in the otherwise colourless membrane. Their object is to open and close communication between the intercellular space always existing between the individual cells and the onter atinosphere. The sausage-shaped cells constituting the essential part of the organ are called the pore cells. They have the power of separating from each other in the middle, thus opening a free way for the air to the interior tissues; or in certain conditions of light and moisture they approach each other so as to narrow or entirely close the slit between them. They are filled with protoplasm, chorophyl and starch granules, while all other cells of the outer surface are filled only with air and water. Apparently with the object of placing these pore cells as free as possible from all constraint or pressure, so that they may correspond sensitively to all the changes in the atmosphere, they are at times situated on a level with the epidermis cells, sometimes raised abore, at others sunk beneath this level. If the epidermis cell-walls are thin and flexible, the stomata will generally be found in the same surface with them; but when the epidermis walls are thick and stiff, the stomata will generally be found sunk deep under the surface, or raised above it, or surrounded by a ring of smaller cells with thinner walls than the remaining epidermis cells. Immediately under the stomata are empty spaces, of irregular form and varying size, called breathing-rooms. They are in connection with, and form a part of the intercellular space which ramifies through the entire structure of most tissues. It is an interesting question in what way the stomata have been formed. Were the pore cells at first a pair of ordinary cells, which have gradually changed their form and contents until endowed with all the peculiar properties of their natural state? Or were they always existent in their peculiarities, only emaller as the leaf was younger? Or, hare they grown out of a single cell by the process of subdivision and after-growth? Do they belong to the epidermis, or to the chlorophyl-bearing tissues beneath ?