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is, that the potato is not the plant on which the fungus luxuriates to the greatest extent, and that if we only knew the plant it most affects (probably some South American species of Solanum) we should then find plenty of resting spores easily enough; for it must not be forgotten that the potato fungus is by no means confined to the potato. It grown on various species of Solanum besides Solanum tuberosum; it is even not un

frequent on the o woody nightshade of our hedges, and it grows upon the tomato and other solanaceous plants, together with at least one plant which belongs to quite a different natural order. On these latter, however, it

makes less headway than upon the potato. As an instance in point, the allied pest of the garden lettuce may be mentionedPeronospora gangliformis - first des

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cribed by Mr. Berkeley. Here, if the resting spores of the parasite are wanted, they must not be sought for in the lettuce itself, where they are only sparingly produced, but in a plant belonging to the same natural order also commonly

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Fig. 163. Peronospora infestans. Oogonia and Antheridia from badly diseased leaves of Potato, after a week's maceration in water; enlarged 400 diameters. Antheridium= 0004 inch. Oogonium 1001 inch. Coat of Cellulose = '00142 inch.

afflicted with the same parasite, viz. the common groundsel: the resting spores are said to be even more common in sow-thistles than lettuces. Therefore, although it is probable we shall have

yet to look to some other member of the natural order Solanaceae to find the resting spores in any abundance, yet, as the resting spores of the lettuce mould can by searching be found in the lettuce

itself, so the resting spores of the potato fungus have without doubt been found this year in the potato plant.

How this came about is now pretty generally known. Mr. Murray exhibited some specimens of potato leaves badly diseased, before the Scientific Committee of the Royal Horticultural Society. In the corroded spots of these leaves Mr. Berkeley's sharp eye detected dark-brown warted bodies (but no mycelium), which he referred to the genus Protomyces. Assuming these bodies to be the true resting spores, which they doubtlessly are, they were necessarily free, as the coat of cellulose disengages them from the mycelial threads. But some similarly spotted leaves had been previously sent on to me from the Journal of Horticulture, upon which I detected the old potato fungus, mycelial threads within the leaves, and some circular transparent bodies of two sizes, new to me.

In attempting to wash the circular bodies out of the leaves and stems, by maceration in water, 1 found the moisture greatly accelerated the growth of the mycelium, and that the long-sought-for

gonium and antheridium were at length the result. Tuese bodies were at first most sparingly produced, so that for many days, and after most careful searching, I could only find one or two. Afterwards I found them more abundantly in different stages of maturity, especially in the very putrid stems and in the tubers when in the last stage of decomposition. Mr. Berkeley afterwards found them with abundant mycelium, after the meeting of the Royal Horticultural Society, on July 7, where he exhibited a drawing of one resting spore still attached to its thread. Mr. Broome (from material sent by me) has also detected and sketched, together with the immature spherical bodies, one of these brown, coarsely-marked resting spores, but it was so involved in the mycelial threads (so he writes me) that he could not set it free. It is quite possible that the condition of the potato, as seen during the present season, is quite exceptional, and that it may not occur again for a long series of years. Mr. Broome has written me to say he has never seen anything similar in diseased potatoes.

In the preceding illustration, which is an exact copy of the first sketch taken, the oogonia and antheridia are seen in the substance of the lamina of the leaf, the two bodies being in contact at H J. In fig. 163 many more of the same bodies are shown; some in actual contact. The two upper figures, K and L, show the resting spores some time after fertilization, when a coat of cellulose is the result. In K the spore is surrounded by this coat, whilst at L the spore is accidentally washed out by maceration in water. The semi-mature resting spores, as shown in these figures at M M, are furnished with a dark coat or skin; this coat, when further maturity is reached, clearly resolves itself into two

layers, the inner one being termed the endospore, and the outer, which in Peronospora infestans is almost black in colour and warted, the exospore. The latter resembles in outward aspect, instead of one spore, a dense concreted mass of minute brownblack bodies. The antheridia are shown at N N. The perfected resting spores are slightly eggshaped, and on an average are one-thousandth of an inch in diameter. The oosphere is fertilized by the contact of the antheridium; when the two bodies accidentally touch, the latter fixes a small branch or tube, called a pollinodium or fecundating tube, into the wall of the oogonium, and discharges part of its contents into the protoplasm of the infant resting spore. When these resting spores are mature, the mycelial threads soon vanish, and the spores are free.

When I read my first notes before the Royal Horticultural Society, I had not been able to detect this fecundating tube, but since then I have several times seen it. After the potato plant has been badly attacked and destroyed by the fungus, every part of the plant and its parasite perishes, except the dark-brown warted resting spores just described, and these find their way into the earth and hibernate. When they awake to renewed life in the summer, they must germinate in the damp earth, and if no potato plants are near, they perish, as the earth cannot support them. In this they are not unlike the seeds of germinating Dodder; for if they cannot find a proper host they die. But if potato plants happen to be near the corrosive mycelium, it at once penetrates and enters the tuber or haulm. The tuber cannot produce simple or zoospores if buried, but in the haulms the mycelium doubtless soon grows and produces both these forms of fruit. These are at once carried by the air into the breathing pores, and the whole history of the fungus here described is re-enacted.

Since my observations on these bodies were published in the Gardeners' Chronicle for July 10, I have (by the courtesy of the Rev. M. J. Berkeley) had an opportunity of carefully examining and measuring the original specimens of Dr. Montagne's artotrogus, found long ago in the intercellular passages of spent potatoes, and from the first considered to be the secondary form of fruit of the Peronospora by Mr. Berkeley. I have no hesitation whatever in saying that the bodies lately seen, and now figured by me are positively the same with Dr. Montagne's in every respect, and when reflected and traced with the aid of a camera lucida no difference whatever can be detected. The bodies seen in Dr. Montagne's specimens are, without doubt, the fertilized and half-mature resting spores, and therefore dense, uncollapsed, and exactly the same in size, habit, and colour with mine when in the same stage of growth. After the lapse of so many years the threads, as might be expected, have more

or less perished, but, it is not difficult to find traces of antheridia in the specimens.

For comparison, the original figure of artotrogus (fig. 161) is here exactly reproduced to the same scale as my drawings, from vol. i. of the Journal of the Royal Horticultural Society, to show the similar nature of the bodies illustrated. Since this was engraved, Mr. Berkeley has kindly forwarded Dr. Montagne's original drawings to me for examination, and I may as well say they contain many more threads and oogonia than are shown in this cut, and they are also more like my organisms now brought forward. As for some of the bodies being shown as if within the threads by Dr. Montagne, I consider this of little moment, as the oogonia are at times almost or quite sessile, and consequently, when seen in some positions, they put on an appearance of being within the mycelium, whilst in reality they are upon or under it. As for the echinulate body at o, described as a "mature spore," it is not exactly like Dr. Montagne's original drawing, which is shown as furnished with a thick wall, and there are no “mature" spores in his specimens. After a most careful and searching examination of the latter, I can find no such bodies, but there are several spores on the two mica slides which put on a spuriously echinulate appearance, which is owing to the collapse of the coat of cellulose, as suggested by me as a possibility when I read my first paper.

It will be observed there is a little difference in

size between my oogonia (fig. 163) and those copied from the Journal of the Royal Horticultural Society; this is because the figures in the latter are somewhat incorrect. When the actual specimens are examined and measured side, by side they are in every way identical.

Mr. Berkeley has also most obligingly sent me a specimen of another (new species?) of Artotrogus, found in decayed turnip by Mr. Broome in 1849. Here the threads and semi-mature bodies are in the same style as the oogonia and threads from the potato, and the mature spore is not truly echinulate; it is globular, with a slight tendency to an oval shape, and is covered with warts. It is probably the resting spore of Peronospora parasitica, the pest of the cabbage.

In figs. 162 and 160 are given copies of the oogonium and antheridium of Peronospora umbelliferarum and P. alsinearum, enlarged from De Bary to the same scale as the other figures, to show the close similarity in size and habit.

(To be continued.)

"THE SWALLOWs, loth to leave us, linger on far into the autumn, and only bid us adieu when they miss the genial influence of the sun's rays, and can no longer find a sufficient supply of food."-Harting's Summer Migrants.

MICROSCOPY.

SEEDS AS OPAQUE OBJECTS FOR THE MICROSCOPE.-"F. E. Fletcher" and others will find the following seeds good microscopic objects for low powers-Portulaca oleracea, Silene pendula, Loasa aurantiaca, Paulonia imperialis, Lychnis floscuculi, Antirrhinum majus, Eschscholtzia termiflora, Stellaria media, Galinsoga parviflora, Nemesia compacta, Hypericum pulchrum, Sphenogyne speciosa.* Glycerine is, perhaps, one of the most troublesome media to keep within the bounds of the cell; but the following cement will, if properly applied, do so. Gold-size, white-lead, red-lead, and litharge; it must be made thin enough to work freely with the brush. This cement should only be made in sufficient quantity for present use, as it soon hardens and becomes useless. Care must always be taken to cleanse the slide and cover of any glycerine that may have escaped: the cement should be used in successive layers, allowing the first to harden before applying a second. I am informed that the flake white (mixed with oil) sold in tubes for the use of artists, to which a little dammar varnish should be added, is also an excellent cement.-F. K.

SEEDS FOR THE MICROSCOPE.-The following small seeds will prove interesting objects under a low power and good reflected light:—Digitalis purpurea, Antirrhinum majus, A. orontium, Linaria cymbalaria, L. purpurea, L. vulgaris, L. minor, L. spuria, and the seeds of Scrophulariaceae generally. The Bignoniacea are interesting, on account of the varying development of a beautiful winged appendagee. g. Paulonia imperialis Eccremocarpus scabra, Nemesia versicolor, Lophospermum scandens, &c. The Ranunculaceæ furnish many beautiful specimens; as, Nigella damascena, Cimicifuga racemosa. The Papaveraceæ are also interesting, as also the genus Campanulæ, and the whole of the Caryophyllaceæ. There is plenty of opportunity for research, as only a hundred or two of minute seeds, so far as the writer knows, have been examined.-W. T. S.

GLYCERINE MOUNTING.-Glycerine is difficult to keep in a cell, but it can be done effectually by careful manipulation. The proper cement is the solution of shellac in wood naphtha, known as "liquid glue" or "patent knotting varnish." The object being placed in its cell, and the cover put in posi tion, the surplus glycerine is to be carefully cleared off, so as not to disturb the cover; first, by absorbing as much as possible by the delicate application of shreds of blotting-paper with the forceps, afterwards clean off as much glycerine as possible with a

"One Thousand Objects for the Microscope,” by M. C. Cooke, gives figures and descriptions of many kinds of seeds and pollens.

wet camel-hair pencil; then carefully varnish by hand, not on the turntable, for fear of disturbing the cover, running the varnish into the angle formed by the junction of the cover and cell, and including the smallest possible portion of both cover and cell; next day, when the varnish is dry, place the preparation under a stream of water, either a tap turned gently on, or the wash-bottle, to wash away the whole of the glycerine from the surface of cell and cover, as until this is done effectually the varnish will not adhere and make a good joint, hence the reason of covering the smallest possible space with the first coat of varnish. Dry carefully, and then revarnish. The turntable can now be used: if there is any doubt about the removal of surplus glycerine, wash again. Repeat the varnishing until a good amount is accumulated, not neglecting the junction of the cell and slide. As the shellac varnish becomes somewhat brittle after a time, give a few coats of gold-size for further security; gold-size is the most reliable of varnishes, and stands well so long as contact with the almost universal solvent glycerine is prevented. The system of compound varnishing is useful in many other cases where the varnish used in retaining the fluid is not altogether reliable.-W. T. S.

MOUNTING MITES.-For mites try castor; it succeeds well with some insects. Place the insects in a bottle of the oil, and leave until required for mounting; the longer the better. Liquid glue is the proper cement, followed with gold-size (see reply to "F. E. Fletcher," on "Glycerine Mounting"); very great care is required in cleaning off the surplus oil from the cell and cover; it is best done with a camel-hair pencil moistened with benzole. Unless every trace of grease is removed, do not expect the varnish to hold. Weak alcohol can be kept in with gold-size. For strong alcohol try gelatine, followed by gold-size; respecting this the writer has no experience.

CLEANING DIATOMS.-The following quotations from "The Microscope and its Revelations" will doubtless supply "St. T. H." with the information he requires. After describing the treatment of the diatomaceous deposit with acids, Dr. Carpenter goes on to say (5th edition, p. 344):-"The separation of siliceous sand, and the subdivision of the entire aggregate of diatoms into the larger and the finer kinds, may be accomplished by stirring the sediment in a tall jar of water, and then, while it is still in motion, pouring off the supernatant fluid as soon as the coarser particles have subsided; this fluid should be set aside, and as soon as a finer sediment has subsided it should again be poured off; and this process may be repeated three or four times at increasing intervals, until no further sediment subsides after the lapse of half an hour. The

first sediment will probably contain all the sandy particles, with, perhaps, some of the largest diatoms, which may be picked out from among them; and the subsequent sediments will consist almost exclusively of diatoms, the sizes of which will be so graduated that the earliest sediments may be examined with the lower powers, the next with medium powers, while the latest will require the higher powers."-W. R. H.

ON MOUNTING.-Mastic is not soluble in turpentine, spirit being the best solvent; it is also soluble in chloroform, but, like many other gum resins, it contains several constituents, some of which are insoluble in spirit, some in turpentine, and some in chloroform. The evaporation of any of the solvents would throw down the resin it had held in solution, and a pseudo-crystalline appearance would become visible, as seen in all the slides mounted in medium named. Why not use pure Canada balsam? Twenty-five years' experience in mounting Diatomaceæ satisfies me that no medium is so suitable, and none easier to use, provided it has not been mixed with benzole, turpentine, or chloroform, either of which will produce bubbles. When the slide is heated, pure balsam may be hardened without air-bubbles making their appearance. Dilute gum-water is the only medium I know of fixing diatoms, &c.-F. K.

INTERFERENCE OF LIGHT.-In using my objective (100°) with second eye-piece, I find the centre of the field filled with a peculiar brightness that seriously interferes with my view of the object. Can any one tell me what is the cause, and how to get over it ?-J. G. R. Powell.

ZOOLOGY.

WHITE WOODCOCK.-It may interest your readers, who, like myself, are lovers of ornithology, to state that a white woodcock (Scolopax rusticola), a male, was shot on Strensall Common, near York, in October last, and is now in my possession. I think it is unusual to meet with white specimens of that bird.-C. D. Wolstenholme.

SCARCE PAINTED LADY.-It may be interesting to your readers to know that I caught on the 2nd of September, a good full-sized specimen of the scarce "Painted Lady"(Cynthia Huntera), at Hayling Island, Hampshire. I have not heard of the capture of this rare butterfly in this district before.-H. W. L.

GREEN SANDPIPER.-It may interest some of the readers of this paper to know that a friend of mine shot on the 15th of August last, a fine specimen of the Green Sandpiper (Tringa ochropus), near Woodbridge, in Suffolk. It perfectly answered to the description given of it in Morris's "British Birds,"

being specially noticed by the white streaks down its tail-feathers, when it was in flight. I should be glad to know if any other specimens have been shot lately in that county or the neighbouring ones.C. W. H.

RETURN OF OUR SUMMER MIGRANTS.-A correspondent at Port Said, in Egypt, writing on the 9th of last month, reports the arrival in Africa of many birds that have been spending the summer in this country. "Ever since the commencement of September," he says, "quail have begun to arrive from Europe, and have been followed by the cuckoo, nightjar, hoopoe, turtle dove, wheatear, teal, and duck, while each day brings flocks of smaller birds whose names it is not in my power to give. Even a few swallows have already put in an appearance'; but one swallow does not make a winter, as a still warm sun reminds one."

THE HOUSE-FLY (Musca domestica).-The familiar house-fly is apt to be considered an unmitigated pest. It is therefore time to call attention to some recent investigations of a chemist, which go to bear out the pious axiom that everything has its use. This observer, noticing the movements of flies after alighting, rubbing their hind feet together, their hind feet and wings, and their fore feet, was led to explore into the cause, and he found that the fly's wings and legs, during his gyrations in the air, become coated with extremely minute animalculæ, which he subsequently devours. These microscopic creatures are poisonous, and abound in impure air, so that flies perform a useful work in removing the seeds of disease. Leanness in a fly is prima facie evidence of pure air in the house, while corpulency indicates foulness and bad ventilation. If these observations are well founded, the housekeeper instead of killing off the flies with poisonous preparations, should make her premises as sweet and clean as possible, and then, having protected food with wire or other covers, leave the busy flies to act as airy scavengers.

GILBERT WHITE OF SELBORNE.-A very interesting series of unpublished letters (ten in number), from the Rev. Gilbert White, author of the "Natural History of Selborne," to Robert Marsham, F.R.S., Stratton Strawless, were read by the secretary of the Norfolk and Norwich Society, at their last monthly meeting. The letters were written between Aug. 13, 1770, and June 15, 1773. The contents consist of remarks on arboriculture; remarks on the rainfall; gossip about birds and insects; and the conformation of Mr. Marsham's supposed discovery of a bird new to Britain, the Wall-creeper or Spider-catcher (Certhia musaria, Tichodrovia musaria); extracts from his brother's -the Rev. John White, of Gibraltar, who resided

there in '1756-unpublished "Natural History of the Rock," in which he describes the difference between the Crag Swallow and the Sand Marten; the former he names Hirundo hyemalis," from the great numbers that frequent Gibraltar in the winter season. The last letter of the series is dated June 15,1773, and is probably the last he ever wrote, as he survived only eleven days. It is the intention of the Society to publish these interesting letters in the next part of their Transactions.

CRIMSON-SPECKLED FOOTMAN.-I am pleased to be able to record the occurrence here of a specimen of the Crimson-speckled Footman (Deiopeia pulchella). It was brought to me on the 17th of this month by a little boy who had taken it in a field near here. It was still alive when I received it, notwithstanding some very rough usage it had received in being captured. Sphinx Convolvuli, too, seems to be rather common this season.-E. 4. Butler, Hastings.

BOTANY.

AUTUMNAL FLOWERING OF SPRING WILD PLANTS.-Gentian, primrose, auricula, or other garden spring plants, as your readers are aware, frequently flower again in autumn; and it is not unusual, as some of them may also have remarked, for certain spring wild plants to do the same. Although the daisy, as the poet says, "never dies,” yet often at this season it shows a tendency to recover from its late summer deterioration by putting forth "in many a greene mede" a fair sprinkling of starry blossoms. The White and Red Archangels (Lamium album and purpureum), though they bloom more or less throughout summer, also appear to receive a fresh impulse and "breathe a second spring." The Crosswort (Galium cruciatum) not only starts life anew, but flowers until frost puts an end to its career. The Rough Chervil (Chœrophyllum temulentum) and other early umbelliferæ make an effort in the same direction; but in some specimens it seems rather involuntary, as the blossoms issue from plants that flowered in spring, and now bear umbels of fruit. The Rough Chervil is singularly interesting in this condition, from the colour of its foliage, which, the first flowering hardly over, turns bronzy-red, crimson, or dark brown, making, especially at that time, while it is as yet early summer, a strange contrast to the bright green in which all other surrounding plants are clad. But the autumnal flowering of the earliest member of the order, the Cow-weed Chervil (Anthriscus sylvestris) is the most noteworthy instance of the kind that we have seen, as we believe it uncommon for this plant to flower a second time in the year, as we saw it flowering, in September.-Richard Dickinson.

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