destroys the matrix on which it grows, and causes the leaves to putrefy and dry up. Perfect specimens are seldom [met with on potato stems; but the destructive mycelial threads descend them, and so reach the tuber. The stem now, like the leaves, rapidly rots, and falls upon the earth an offensive mass. So rapid and fatal is the growth of this fungus, that in a few days it will spread from plant to plant over a large tract, and in less than a week turn every stem and leaf in the field to one rotten mass. Within these diseased stems are often found black masses of hardened

similar threads have also been found on the woodwork of old coffins. Returning to the young condition of the potato fungus, we see it five days old in fig. 153, where the distance from A to B shows the thickness of the potato-leaf itself, magnified 400 diameters: A is the upper surface of the leaf, and B the lower. The mycelial threads or spawn, C, may be seen ramifying amongst the cellular tissue of the leaf, whilst the fertile thread is shown emerging through a breathing-pore, or stomate, D, and branching and bearing (at present) immature spores at E.

the characteristic swellings on the branched threads are shown, the stems bearing an abundance of spores (which are analogous with seeds and reproduce the parent) on their apices; the threads, as in the last figure, are seen emerging through a breathingpore on the lower surface (here inverted, better to display the character of the fungus).

It is easy to see from this figure the damaging effect the fungus must have upon the plant: the fungus stems protrude from its mouths, and prevent the emission of perspiration; the potato-plant thus gets surcharged with moisture, which rots the stems and leaves, whilst the mycelium preys upon the tissues.

Пороо

H

Fig. 155. Peronospora infestans, spores and zoospores, enlarged 400 diameters.

:

When the mature spores (G, fig. 155) fail from their apices, they readily germinate, as at H, H, by rupturing their outer coat, and discharging their contents these contents immediately take the form of confluent mycelial threads, and produce the characteristic brown colour in the cellulose. The spores in this figure are enlarged 400 diameters, or to the same scale as fig. 153. In fig. 153, however, it must be remembered that the spores represented are immature. In the perfect condition of the potato fungus, certain privileged spores acquire greater dimensions than others, as shown at J, fig. 155; the contents of these privileged spores become differentiated, and produce within themselves a number of distinct nucleated cells, which at length are set free in the form of active zoospores, each zoospore being furnished with two thread-like processes (K), with which, when in fluid, they are enabled to move rapidly about. These bodies germinate exactly in the same way as the ordinary spores, by discharging their contents through the ruptured outer coat (L), and must play a very important part in the economy of the plant, for it is manifest that although they cannot move unless immersed in fluid, yet it can easily be imagined that during

Fig. 156. Peronospora infestans, spore germinating, enlarged 400 diameters.

Fig. 156 shows a section through the stalk of a potato-plant, with a single mature spore germinating upon the surface, its mycelium penetrating the epidermis (M) and cortical layer (N N).

Now, not only is Peronospora infestans able to reproduce itself from its spores and zoospores, but amongst the mycelium in the intercellular passages of spent potatoes are found other bodies which there grow and fructify. These bodies, discovered by Dr. Payen, though referred to the Sepedoniei by Montagne (the order next in succession to Mucedines, to which latter order the genus Peronospora belongs), are considered by Berkeley and others to be probably a secondary form of fruit (oospores) of the potato fungus itself. These bodies, named by Montagne Artotrogus hydnosporus, are shown in

Fig. 157. Artotrogus hydnosporus, enlarged 400 diameters.

fig. 157 magnified 400 diameters; the young Artotrogus being shown at O in its mother cell (with threads), and at P free.

These bodies make the study of the potato disease more complicated, and its ultimate eradication far more difficult; for they do not germinate at once (as do the spores and zoospores), or perish, but remain quiescent for a whole season, till certain favourable external conditions cause them to burst from their sleep and reproduce the parent. Resting spores and dormant sclerotioid tuberiform bodies are very common amongst fungi, a very remarkable instance being found amongst the Agaracini. In Agaricus tuberosus, we have an agaric springing from a tuberiform base, which is invariably found growing from the dead remains of the previous year's fungi, generally the Russula; but we have found the sclerotia at the bottom of the tubes of some of the Polyporei, the perfect agarics emerging through the tubes.

Closely allied to the potato fungus is another species found infecting chickweed (Stellaria media), and named by Casparry Peronospora alsinearum. In this species, and some others of the genus, male organs, or antheridia, have been detected, as shown at Q, fig. 158, where the mycelial filaments are shown

W.GS

Fig. 158. Peronospora alsinearum, enlarged 400 diameters.

bearing the oogone, with which the mature antheridium is shown in contact: the contents of these cells are interchanged, and thus an oospore or resting spore is produced. At R is shown a section with the inflated summit of the fecundating tube of the antheridium (X) touching the gonosphere: this latter has a neat outline, produced by the membrane of cellulose which has just been secreted.

At fig. 159 (S) is shown a ripe oospore, furnished with its thick reticulated epispore, the surrounding protoplasm having almost disappeared; and at Ta ripe oospore, whose epispore has been detached by maceration in water; a thick, colourless endospore remaining, composed of two thick layers containing protoplasm, with two unequal vacuities. The fecundating tube may be seen still fixed in the endospore at U. These oospores, or resting spores, of the chickweed parasite, like those of the potato, possess the singular property of remaining dormant during the winter, and germinating (under favourable circumstances) during the following season.

We have now glanced at the fungus and its

Fig. 159. Peronospora alsineraum, enlarged 400 diameters. arrested; but if the plants are well established, the tubers are found to be discoloured. This is undoubtedly caused by the presence of the fungus beneath the cuticle of the potato; for if the potatoes are taken up and kept in a damp air for a day or so, the perfect parasite presents itself upon the surface. From the exterior of the potato the fungus penetrates to the interior, decomposing the tissues, and making the tuber a suitable nidus for various other fungi, which are not long in making their appearance. With the decomposition comes the disgusting odour so well known in connection with diseased potatoes; the diseased tuber is now attacked by insects, and its end is one horrible foetid mass. It generally happens that the eyes are the last to succumb to the disease; and it is stated, that if these are cut out and planted, they grow into healthy plants; but if the fact is taken into consideration of the resting spores being produced within the intercellular passages of spent potatoes, and that these resting spores are capable of lying dormant during a whole season, it seems reasonable to imagine that the planting of such eyes would be the one certain means of spreading the disease.

That the fungus attacks apparently healthy plants there can be no manner of doubt, the prevailing opinion now being that it is by no means necessary that a plant should be in ill health for a fungus to find thereon a suitable nidus. Contrary opinions have, however, long been held, and are still held on this point, many observers thinking that excessive moisture, over-cultivation (if such a thing be possible), electrical influences, or attacks of insects, first affect the health of the plant, and predispose it to succumb before the attacks of the fungus. Mr. Alfred Smee, surgeon to the Bank of England, has long held his ground upon the hypothesis that the potato is first attacked

by an aphis, and so rendered a ready prey to the Peronospora, and says from his own observations he believes that an aphis invariably punctures the leaves before an attack of the fungus: he holds the same views with respect to the Ascomyces of the peach; but Berkeley and others nail their colours to the fungus, the whole fungus, and nothing but the fungus, and not without sufficient grounds; for, amongst other reasons, the immediate allies of the potato fungus do not prey upon decaying matter; other species of fungi do, but these do not. Whilst it is comparatively easy to say when and where the potato murrain was first brought prominently into notice, and what the potato disease is, it is by no means an easy matter to suggest an effectual antidote to its ravages. Dr. Hooker has recently published in the daily papers a plan devised by Professor Henslow for preserving the nutritive portions of diseased potatoes; but, from its tedious nature, it is never likely to be carried out to any extent, or made use of by the people at large. When the disease first appeared, a quarter of a century ago, it was suggested that the moment it became manifest in the leaves the whole crop should be mown down and burnt before the destructive virus reached the tubers. Now, after all this lapse of time, no better plan can be suggested; but such is the rapid growth of the fungus, that unless the haulms be destroyed immediately on the appearance of the parasite, it will be too late: if a week or less be allowed to elapse, the mycelium will be in the tubers, and all the haulms a rotten

mass.

In the case of the vine disease, sulphur has been found very efficacious; but it is impossible to apply the fumes of sulphur to the potato crops. Mr. Smee has destroyed Oidium in his grape-house with the fumes of bisulphide of carbon; but it is not easy to see how any fumes can be applied in the open fields.

It has recently been said that it is a disgrace to science and to scientific men that no perfect remedy has yet been found for the ravages of the potato disease: the same may be said, I presume, respecting the ravages of the rinderpest, foot-and-mouth disease, and cholera itself; but I fail to see the disgrace to "scientific men." If there is any disgrace in the matter, it rests with those persons who are commercially interested in the success of our potato crops; for, although we have had the fatal disease amongst the potatoes for a quarter of a century, these gentlemen have still the stupidest possible ideas of what it is, and how to cope with it; as is abundantly proved by the melancholy balderdash recently printed in the newspapers.

12, North Grove West, Mildmay Park, N.

CANDOUR forbids me to say absolutely that any fact is false because I have never been witness to such a fact.-Gilbert White.

ANCIENT STONE IMPLEMENTS.*

TRULY a magnificent work, and one that will delight the eyes of every antiquary and geolo

gist in Europe! It deals with one of the most interesting and important of subjects, the antiquity of the human race, and the stages through which poor humanity passed in its struggles to the light of civilization. Before written history commenced, a vast period had elapsed, compared with which that circumscribed by legendary and historical literature is but a span. Until the last few years, all our knowledge of this epoch was most meagre; for, accepting the long-taught doctrine of the appearance of nian upon the earth being merely a few thousand years, all, or nearly all, of which was included in written history, we never guessed at the marvellous story that was hidden up in our valley gravels and bone caverns. And now all this is becoming more or less clear. Such antiquaries as Nilsson, Lyell, Perthes, Tylor, Lubbock, and Evans have done for pre-historic times what was so successfully effected only a few years ago in architecture, when all the mixed jumble of archæological lore was reduced to the historic orders of "Norman,' Early English," "Perpendicular," "Decorated," &c., and it was discovered that every old church before the Reformation might easily be referred to one of these periods by its architectural characters. The Danish antiquaries, we say, did the same by ancient stone and other implements and bronzes, and thus founded the divisions of Early Stone Age (Palæolithic), Newer Stone Age (Neolithic), Age of Bronze and Age of Iron. Although none of these is rounded off by a definite sharp line-any more than the architectural periods are-yet they are sufficiently useful for classification, and to a wonderful extent convey the actual truth concerning them.

Mr. Evans stands in the foremost rank of pre-historic workers. None has more than he helped to clear up those "dark ages" when Great Britain was, as regarded her inhabitants, for a long period in the condition that Captain Cook found the aborigines of the South-Sea Islands. His keen, almost intuitive, knowledge of ancient stone implements is well known to every collector. So indefatigable has he been that every fresh "find" has at once brought him down. He has so entered into the spirit of how these wonderful stone weapons were formed without the aid of other tools than natural pebbles or boulders, that he has made them himself with such aid, and has patiently worked with stick and sand until he, like some of his earlier and no less skilful ancestors, produced a stone hammer with a hole through for the handle! Not

"The Ancient Stone Implements, Weapons, and Ornaments of Great Britain." By John Evans, F.R.S., F.S.A., &c. London: Longmans & Co. 1872.

withstanding the variety of type of the ancient weapons and ornaments, it is wonderful how those of every country resemble each other, plainly proving that the places where stone and flint implements are still in use, are, to use a geological phrase, merely "outliers" of a once universal condition. We proceed to illustrate our remarks by

specimens, the blocks of which have been kindly lent us by the publishers for the purpose.

Fig. 160 is one of the earliest, or Paleolithic types of flint weapons, obtained by striking the piece longitudinally off a core. The implements obtained in our valley gravels, in the terraces above the present levels of rivers, are frequently of this shape. From this earliest and rudest of forms we have a gradual transition in the specimens to those of the latest Neolithic period, when their art development reached its highest finish. Fig. 161 is a

Fig. 163. Palæolithic Flint Imple ent, from Pressigny.

Fig. 162. Neolithic Implements.

was found indicate it to be of a more recent date than the preceding. Fig. 162 is from the same place, and is still more neatly finished. All these