; D Si ae Rust i MILDEW: & MOULD. jj! e 6° e MC COOKE Py Ss Cornell University Library OF THE ‘| Rew Work State College of Agriculture “6 O36 Pay Library Bureau Cat. No. 1137 [ Corneil University Library QK 601.C7 1902 Ru .An introducti st, smut, mildew & mould I) | 3 1924 001 8 33 239 sam Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu3 1924001833239 RUST, SMUT, MILDEW, & MOULD. WORKS BY THE SAME AUTHOR, A plain and easy Account of the British Fungi. With especial reference to the Esculent and other Economic Species. Third Edition, revised. With Coloured Plates of 40 Species., Feap, 8vo., cloth, 6s. A Manual of Botanic Terms, New Edition, greatly enlarged, including the recent Terato- logical terms. Dlustrated with more than 300 Woodcuts. Feap. 8vo., cloth, 2s. 6d, A Manual of Structural Botany. Revised Edition, with New Chemical Notation. Twentieth Thousand. MTlustrated with 200 Woodcuts, ls. W. H. ALLEN & CO., 13 WATERLOO PLACE. S.W. RUST, SMUT, MILDEW, & MOULD. AN INTRODUCTION TO THE STUDY OF MICROSCOPIC FUNGI. BY M. C. COOKE, M.A., LL.D., A.L.S., SIXTH EDITION, REVISED AND ENLARGED. ILLUSTRATED WITH 269 COLOURED FIGURES By J. B. SOWERBY. LONDON: W. H. ALLEN AND CO., 13 WATERLOO PLACE, S.W. 1902 F mw CONTENTS. 2 eee CHAP, PAGE Ee QGUSTRR COBB 5h ccs ca casncsahacean denon sueSawesceaitodnsves 1 TT, SPBRMOGONES vise ccnasagil cscs semdleny pease vlesgamiezeip goss 23 TIT, DI-MORPHISI sesssiessecwseveseoees merceiwcess cexomencn 32 IV. MinpEWw AND BRAND ..... .o..cceeececeeecteeeeecn anes 45 V. CompLex BRANDS .o...... cecceceeeteeeeceesen seen eenaee 67 Wil SMUT ic iris inae gutteiantnstecmanraners -benden madaade emake 77 VIT. Complex -SmMUTS sstssevscssrevcssssene sususvensverser sor 90 WALID: RUST ycaeia ie seeded inmaeesaeoss Diadiodansieabagausaauatedes ue 95 EX, RUSTS: (CONC) x. ie csi pasiciacteiciewes do Shtagiguesiielaggsis i10 XK, Ware; RUSTS cxswsesesxerscsssenesensancsnn veeweeaves 124 MET. MOULDS: sc ssiaxeenca estes teeancens tea tacaievaetassaationees 138 XII. Waitt Miupews or BLIGBTs .............. cee 164 AELIL,, SUGGESTIONS 6 sce s2ccawin teense satasdsnweinmindie auloninneigeele 181 APPENDIX, CLASSIFICATION, AND DESCRIPTIONS OF Funai conTAINED IN THIS VoLUME,. ......... 193 MICROSCOPIC FUNGL CHAPTER L CLUSTER-CUPS. N these latter days, when everyone who possesses a love for the marvellous, or desires a knowledge of some of the minute mysteries of nature, has, or ought to have, a microscope, a want is occa- sionally felt which we have essayed to supply. This want consists in a guide to some systematic botanical study, in which the microscope can be rendered available, and in which there is ample field for discovery, and ample opportunity for the elucidation of facts only partly revealed. Fungi, especially the more minute epiphyllous species, present just such an opportunity as many an ardent student would gladly take advantage of; one great obstacle to the pursuit being, until lately, found in the absence of any hand-book to this: section of the British Flora embracing the emen- dations, improvements, and additions of the past forty-two years (the period at which the fifth B 2 MICROSCOPIC FUNGI. volume of the “English Flora” made its appear- ance). It would be incompatible with our object, and beyond our limits, to introduce an entire mycological flora to our readers in these pages; but we hope to communicate such information as will serve as an introduction to certain sections of the Handbook of British Fungi, and render the demand still wider and more general for such an extension of our botanical literature. When the early editions of this book were issued, no other detailed account, or figures, of the ‘objects it con- tained could be found in this country; but, although such is not now the case, it still remains unique in its character. Let not the reader imagine, from what we have just stated, that it is our intention to burden him with a dry series of botanical descriptions ; as much of this as we deem essential to render the book available to the botanical student, we have pre- ferred to add in the form of an Appendix. Useful as these may be to some, we hope to be en- abled to furnish for others something more; and although we at once disclaim any intention of including all the microscopic, or even the epiphytal fungi, in our observations, yet we trust, by a selec- tion of common and typical species for illustration, and by an adherence to certain well-defined groups and sections, to demonstrate that the microscopist will find an eligible field for his observations in this direction, and the botanical student may gain CLUSTER-CUPS. 3 some knowledge of their generic and specific dis- tinctions. It is exceedingly difficult to give a logical defi- nition of what constitutes a fungus. It is no less difficult to furnish a popular description which shall include all and nothing more. If, for example, we particularize the spots and markings on the leaves and stems of herbaceous plants, so commonly met with from early spring till the fall of the last leaf, and even amongst the dead and decaying remains of the vegetation of the year, we may include also such spots and marks as result from insect depre- dations or diseased tissue. It is not always easy, with a cursory: observation under the microscope, to determine whether some appearances are pro- duced by fungi, insects, or organic disease: expe- rience is the safest guide, and until we acquire that we shall occasionally fail. If we take a stroll away from the busy haunts of men, though only for a short distance,—say, for example (if from London), down to New Cross, —and along the slopes of the railway cutting, we shall be sure to find the plant called the goatsbeard (Tragopogon pratensis) in profusion. In May or June the leaves and unopened involucres of this plant will present a singular appearance, as if sprinkled with gold-dust, or rather, being deficient in lustre, seeming as though some fairy folk had scattered over them a shower of orange-coloured chrome or turmeric powder. Hxamine this singular B 2 4 MICROSCOPIC FUNGI. phenomenon more closely, and the poetry about the pixies all vanishes; for the orange powder will | be seen to have issued from the plant itself A pocket lens, or a Coddington, reveals the secret of the mysterious dust. Hundreds of small orifices like little yellow cups, with a fringe of white teeth around their margins, will be seen thickly scattered over the under-surface of the leaves. These cups (called peridia) will appear to have burst through the epidermis of the leaf and elevated themselves above its surface, with the lower portion attached to the substratum beneath. In the interior of these cup-like excrescences, or peridia, a quantity of the orange-coloured spherical dust remains, whilst much of it has been shed and dispersed over the unoccupied portions of the leaves, the stems, and probably on the leaves of the grass or other plants growing in its immediate vicinity. These little cups are fungi, the yellow dust the spores,* or ultimate representatives of seed, and the epi- phytal plants we have here found we will accept as the type of the group or order to which we wish to direct attention (plate I. figs. 1—8). Amongst the six families into which fungi are divided, is one in which the spores are the prin- cipal feature, as is the aurantiaceous dust in the parasite of the goatsbeard. This family is named * Protospores they should be called, because, in fact, they germinate, and on the threads thus produced the true spores or fruit, are horne. CLUSTER-CUPS. 5 Coniomycetes, from two Greek words, meaning “ dust-fungi.” This group or family includes several smaller groups, termed orders, which are analogous to the natural orders of flowering plants. Without staying to enumerate the characteristics of these orders, we select one in which the spores are enclosed in a distinct peridium, as in our typical plant they are contained within the cups. This order is the Afcidiacei, so called after Avcidiwm, the largest and most impcrtant of the genera included within this order. The Alcidiacet are always developed on living plants, sometimes on the flowers, fruit, petioles, or stems, but most commonly on the leaves: occa- sionally on the upper surface, but generally on the inferior. The differert species are distributed over a wide area; many are fourd in Hurope and North America, some occur in Asia, Africa, and Australia. When the cryptogamic plants of the world shall have been as widely examined and as well under- stood as the phanerogamic plants have been, we shall be in a better position to determine the geographical distribution of the different orders of fungi. In the present incomplete state of our knowledge, all such efforts will be unsatisfactory. But to return to the goatsbeard, and its cluster- cups. The little fungus is called Mecidiwm trago- pogonis, the first being the name of the genus, and ‘the last that of the species. Let us warn the young student against falling into the error of supposing 6 MICROSCOPIC FUNGI. because in this, and many other instances, the specific name of the fungus is derived from the plant, or one of the plants, upon-which it is found, that therefore the species differs with that of the plant, and that, as a rule, he may anticipate meet- ing with a distinct species of fungus on every distinct species of plant, or that the parasite which he encounters on the living leaves of any one plant is necessarily specifically distinct from those found on all other plants. One species of Aicidiwm, for instance, may hitherto have been found only on one species of plant, whereas another AMcidiwm may have been found on five or six different species of plants. The mycologist will look to the specific differences in the parasite without regard to the identity or distinctness of the plant upon which it is parasitic. Before the Acidium breaks through the epi- dermis, the under-surface of the leaves of the goatsbeard will appear to be covered with little elevations or pustules, paler at the apex; these soon become ruptured, and the fungus pushes its head through the opening, at the same time bursting by radiating fissures. The teeth thus formed resemble those of the peristome of some mosses. All around the orifice of the peridium the teeth become recurved, and the orange spores are exposed, crowded together within. At first, and while contained within the peridium, these spores are concatenate or chained together, but CLUSTER-CUPS. 7 when dispersed they are scattered singly about the orifice, often mixed with the colourless cells arising from the partial breaking up of the teeth of the peridium. Let us pause for a moment in our examination of the individual cups, to ascertain their manner of distribution over the leaves. In this instance they are scattered without any apparent order over the under-surface, but generally thickest towards the summit of the leaves; occasionally a few are met with on the upper surface. Sometimes two or three touch at the margins, but we have never met with them truly confluent; generally there is a space greater than the width of the cups around each, the stratum or subiculum from whence they arise is scarcely thickened, and there are no spots or indications on the opposite surface. If a leaf be taken fresh and the cuticle stripped off, which it will sometimes do very readily, the orifices through which the Aicidiwm has burst will appear in irregular holes. If a section be made of one or two of the fungi im situ, they will be seen to spring from beneath the cuticle, the peridium to be simple, and rounded at the base, the spores clustered at the bottom, and the fringe to bea continuation of its cellular substance. The spores in this species are orange, subglo- bose, sometimes angular, and indeed very variable both in size and form, though the majority are comparatively large. Hach of these bodies is, 8 MICROSCOPIC FUNGI. doubtless, capable of reproducing its species, and if we compute 2,000 cluster-cups as occurring on each leaf, and we have found half as many more on an ordinary-sized leaf, and suppose each cup to contain 250,000 spores, which again is below the actual number, then we shall have not less than five hundred millions of reproductive bodies on one leaf of the goatsbeard to furnish a crop of parasites for the plants of the succeeding year. We must reckon by millions, and our figures and faculties fail in appreciating the myriads of spores which compose the orange dust produced upon one infected cluster of plants of Tragopogon. Nor is this all, for our number represents only the actual protospores which are contained within the peridia; each of these on germination may produce not only one but many vegetative spores, which are exceedingly minute, and, individually, may be regarded as embryos of a fresh crop of cluster- cups. And this is not the only enemy of the kind to which this unfortunate plant is subject, for another fungus equally prolific often takes posses- sion of the interior of the involucre wherein the young florets are hid, and converts the whole into a mass of purplish black spores even more minute than those of the Mcidiwm, and both these para- sites will be occasionally found flourishing on the same plant at the same time (plate V. figs. 92—94). Naturally enough, our reader will be debating within himself how these spores, which we have CLUSTER-CUPS. 9 seen, are shed in such profusion, can enter the tissues of the plants which give subsequent evidence of infection; in fact, how the yellow dust with which the goatsbeard of to-day is covered will inoculate the young plants of next year. If one or two of these spores are sprinkled upon the piece of the cuticle which we have recommended to be removed from the leaf for examination, it will be seen that they are very much larger than the stomata or breathing-pores which stud the cuticle: hence it is clear that they cannot gain admittance there. There remains but one other portal to the interior of the plant— namely, the spongioles, or extremities of the roots. Here another difficulty arises; for the spores are as large as the cells through which they have to pass. This difficulty may be lessened when we remember that what are termed the spores which are discharged from the cups are not the true spores, but bodies from which smaller seed-like vesicles are produced ; yet, even then there will be much need of an active imagination to invent hypotheses to cover the innumerable difficulties which would encounter their passage through the vessels of the infected plants. The Rev. M. J. Berkeley proved many years ago that the spores of bunt, for example, may be caused to infect all the plants the seeds of which had been placed in contact with them; but this affection did not necessarily accrue from the absorption of the 10 MICROSCOPIC FUNGI. spores, or the ultimate sporidia produced after three or four generations. It is possible that the granular or fluid contents of the spores may be absorbed by the plant, and as a result of this absorption, become inoculated with the virus, which at length breaks out in fungoid growths. Much has been done to elucidate this mystery of inoculation, but much also remains a mystery still. There is no doubt that the inoculation takes place at an early age,* probably in the seeds of many plants; in others it may be conveyed with the moisture to the roots; but the spores themselves have certainly not yet been traced traversing the tissues of growing plants. If, instead of going in search of goatsbeard and its attendant fungus, we turn our steps northward and enter one of the Highgate or Hampstead woods, where the pretty little wood anemone (Anemone nemorosa) flourishes abundantly, and turn up the radical leaves, one by one, and examine their under-surfaces, we shall at length be re- warded by finding one covered with similar cluster-cups to those we have been describing as occurring on the goatsbeard, but far less commonly. Leaf after leaf will be found covered with the brown spots of another fungus called Puccinia anemones, with which nearly every plant will be * Dr. de Bary has lately shown that in many similar instances the seed-leaves are inoculated. It will be necessary to refer more particularly to his experiments hereafter. CLUSTER-CUPS. 11 more or less infected in the spring of the year; and at length, if we persevere, the anemone cluster-cup (Avcidium leucospermum) will be our reward (plate I. figs. 4—6). The specific name will suggest one point of difference between the two fungi, as in this instance the spores are white, and somewhat elliptic. Probably this species is not common, as we have found it but seldom, though often in search of it. A nearly allied species has been found on Anemones in gardens, having but few large teeth about the orifice, though not constantly four, as the name would indicate (Zi. quadrifidum). A walk through almost any wood, in the spring of the year, will reward the mycologist with another cluster-cup (Acidiwm), in which the peridia are scattered over the whole surface of the leaf. This will be found on the wood spurge, giving a sickly yellowish appearance to the leaves, on the under-surface of which it is found. By experience one may soon learn to suspect the occurrence of parasites of this nature on leaves, from the peculiar exhausted and unhealthy appear- ance which they assume as the spores ripen, and which will spare the labour of turning over the leaves when there are no distinct spots on the upper surface. 4. Huphorbie is found on several species of Huphorbiwum or spurge, but we have always found it most abundantly on the wood spurge in the Kentish woods between Dartford 12 MICROSCOPIC FUNGI. and Gravesend. The spores in this species are orange, and externally it bears considerable re- semblance to the goatsbeard cluster-cup, but the spores are rather smaller and paler, the teeth are less distinct and persistent, the subiculum is more thickened, and the peridia are more densely crowded. There is another group of species belonging to the same genus of fungi in which the arrange- ment of the peridia is different. One of the first of our native wild flowers, in making its appear- ance after the departure of frost and snow, is the little yellow celandine (Ranunculus ficaria). “Ere a leaf is on the bush, In the time before the thrush Has a thought about her nest, Thou wilt come with half a call, Spreading out thy glossy breast Like a careless Prodigal ; Telling tales about the sun When we've little warmth, or none.” And one of the earliest parasitic fungi in spring is an Afcidiwm which flourishes on its glossy leaves. So common is Heidium ranunculacearum on this species of Ranunculus, that it can scarcely have escaped the eye of any one who has taken the trouble to examine the plant. It appears in patches on the under-surface of the leaves or on their petioles, in the latter case swelling and distorting them. Sometimes these patches are nearly cir- cular, at others of very irregular form, and varying CLUSTER-CUPS. 13 in size from less than one-twelfth of an inch to half an inch in diameter. It is found on several species of Ranunculus, as R. acris, bulbosus, and repens, but most commonly on R. ficaria. The leaf is thickened at the spot occupied by the parasite, and generally without indication on the opposite surface. Some- times one spot, at others several, occur on the same leaf. The peridia are densely crowded to- gether, often arranged in a circinate manner, 1.e., like a watch-spring, or the young frond of a fern. The spores are orange, but slightly varying in tint on different species of Ranunculus (plate IT. figs. 12—14). One of the smaller clusters, when col- lected before the spores are dispersed, or the teeth of the peridium discoloured, mounted dry as an opaque object, makes a very excellent slide for an inch or half-inch objective; and the same may be said of many others of the same genus. Less common than the foregoing is the species of Heidiwm which attacks the violet. The sweetest of flowers as well as the earliest, in despite both of its odour and its humility, becomes a victim to one or more of the ubiquitous race of fungi. Thickened spots at first appear on the leaves; the petioles, or flower stem, or even the calyx, become swollen. and distorted; and at length the cluster-cup breaks through. The spots on the leaves upon which the peridia are scattered are yellowish, generally larger than the clusters on the pile-wort, and seldom with more than one spot on each leaf. The peridia, or 14 MICROSCOPIC FUNGI. cups, are irregularly distributed over the spots, not crowded together as in the last species; and the teeth are large, white, and distinct. The spores are at first orange, but at length become brownish. This species may be found in spring, as late as June, most commonly on the dog-violet, but also on other species of Viola. It is not a very desirable occupation to search a bed of nettles, and turn over the individual leaves to look for minute fungi. A very pretty Heidium is nevertheless far from uncommon in such a habitat. Fortunately it occurs very often on the petioles of the leaves and on the stem, distorting them very much ; and in such situations flourishing, apparently, more vigorously than when occupying the under- surface of the leaves (plate I. fig. 10). In the latter situation the clusters of peridia are small, seldom exceeding a dozen in a spot, but several spots may be found on the same leaf. On the stem they are clustered around for upwards of an inch in length, and their bright orange colour in such a situation renders them very conspicuous objects. The peridia are always closely packed together upon a thickened base, and offer but slight variations from the forms already enumerated, save that they widen slightly at the mouth, so as to become nearly campanulate. The spores are orange, and very profuse. During the summer of 1863 we noticed, for the first time, a very pretty little species of cluster-cup (Aicidiwm) on the wood sanicle(Sanicula Huropea) in CLUSTER-CUFS. 15 Darenth wood. It was far from uncommon, and we believe it to be specifically distinct from its nearest ally, found on the earthnut leaves, and those of some other umbelliferous plants. The little cups are in small clusters of four or five together, on the under surface and on the petioles; they are small, but the teeth are relatively large, white, and distinct. ‘The spores are of a pallid, yellowish colour, and not so profuse as in the last species. A darker spot on the upper surface of the leaf generally indicates their presence. This species was found many years ago by Carmichael at Appin, and called by him Aeidium sanicule ; but not afterwards until we found it, though it seems to be far from uncommon at Darenth, and in other places, where the sanicle is common also. Recently we found the bedstraw cluster-cup. (Aicidiwm galt) on the great hedge bedstraw (Galium mollugo), and as it has not been figured before, we have included it amongst our illustrations (plate II. figs. 15—17). Though very insignifi- cant when occurring on the small leaves of the yellow bedstraw (Galium verum), it is a prominent object on the above-named species. We received, for the first time, in July, 1864. from Mr. Gatty, student at Winchester, a portion of a plant of Thesium humifusum (which is by no means common in Britain), covered with beautiful cluster-cups of a species never before recorded 4s occurring in this country (plate III. figs. 50, 51) 16 MICROSCOPIC FUNGL. named Meidium Thesii, but which is far from nncom. mon on the Continent. It occurred in this instance on the Downs, in the vicinity of Winchester. It is unnecessary here to refer to other allied species of AHcidiwm, except one to be pre- sently noticed, since we have, at the end of the volume, enumerated and given descriptions of all the species hitherto found in Britain. Suffice it to say that the Buckthorn cluster- cups on the alder buckthorn (Rhamnus fran- gula), is usually very common in the Highgate and Hornsey woods, and on the common buck- thorn (Rhamnus catharticus) in the neighbourhood of Dartford, in Kent. That on the honeysuckle we have found but very rarely. On the gooseberry and red-currant leaves, commonly in some years and rarely in others; whilst a few of those de- scribed we have never collected. The species on different composite plants is subject to great vari- ation, and on most may be found in the autumn; one variety only, on the leaves of Lapsana communis, we have met with in the spring. Very few years ago farmers generally believed that the cluster-cups of the berberry (Berberis vul- garis), were productive of mildew in corn grown uear them; this opinion even received the sup- port of Sir J. Banks, and recently it has been revived amongst botanists, but is not absolutely accepted, as not wholly proven. In this instance the cups are much elongated, and cylindrical; CLUSTER-CUPS, 17 the clusters vary much in size, and the spots on the upper surface of the leaf are reddish, bright, and distinct. The teeth are white and brittle, and the orange spores copious (plate I. figs. 7—9). There are scarcely any of the epiphyllous fungi forming equally handsome or interesting objects for low powers of the microscope, than the genus to which attention has just been directed; and they possess the advantage of being readily found, for that locality must be poor indeed which cannot furnish six species during the year. We have found half of the number of described species within little more than walking distance of the metropolis, within a period of little more than three months, and should be glad to hear of the occurrence of any of the rest. We have three species of fungi very similar in many respects to the foregoing, but differing in others to such an extent as to justify their associa- tion under a different genus and name. The hawthorn is a bush familiar to all who love the “merry month of May,” but it may be that its parasite has been unnoticed by thousands. If, for the future, our readers will bear this subject in their minds when they stand beneath a hawthorn hedge, they may become acquainted with clusters of sin- gular brown pustules on the leaves, petioles, and fruit well worthy of more minute examination (plate II. fig. 22). They scarcely claim the name of cups, aud their lacerated and fringed margins rather ¢ 18 MICROSCOPIC FUNGI. resemble the pappus crowning the fruits of some composite plants than the cups of Avcidiwm. The peridia are very long, and split down throughout their length into threadlike filaments of attached cells; these gradually fall away and break up into their component parts till but short portions remain attached to the base of the peridia. These cells are elongated and marked on the surface with waved lines, forming in themselves pretty objects for a high power of the microscope (plate II. figs. 23, 24). If the teeth of Acidiwm resemble the peristome of some mosses, such as Splachnum, the threads of this species of Restelia, except in not being twisted, somewhat resemble the peristomes of other mosses of the genus Tortula. The spores in this species are less conspicuous, being of a light brown, and the whole plant, from its modest hue, may be readily passed over without attracting attention unless occurring in abundance. The leaves of pear-trees afford a second species of this genus sufficiently distinct to commend it to our notice. Sometimes it is very common, at others but few examples are to be met with. The clusters occur on the under-surface, and consist of half-a- dozen or less of large peridia, pointed at the apex and swelling in the middle so as to become urn. shaped (plate II. figs. 20, 21). These vessels or thece split into numerous threads or lacinie, which remain united together at the apex. Like the species already noticed, this is brown and incon. CLUSTER-CUPS. 19 spicuous except on account of its size, for it is the largest of all that we have had occasion to notice. The third species occurs on the under-surface of the leaves of the mountain-ash. The peridia are clustered on a rusty orange-coloured spot which is visible on the upper surface (plate IT. figs. 18, 19). They are long and cylindrical, with an evident tendency to curvature; the mouth is serrated, but not split up into threads, as in the species found on the hawthorn. There will often be found instead of well-developed peridia, what at one time were regarded as abortive peridia, forming a thickened orange or rust-coloured spot, studded with minute elevated points. These spots are clusters of spermogones, which organs are described in detail in our second chapter. The clusters and spores are of a brighter reddish brown than in either of the other species. All are remarkably distinct, and perhaps the most curious and interest- ing of any that we have passed in review. To botanists, the species found on the hawthorn is known as Restelia lacerata, that on pear-leaves as Restelia cancellata, and the one on the leaves of the mountain-ash as Restelia cornuta. Dr. Withering observed the spore-spots on the leaves of the mountain-ash, but was evidently puzzled to account for them. He writes (in his Arrangement of British Plants), “The spots on the leaves of Sorbus aucwparta consist of minute globules intermixed with wool-like fibres. On c2 20 MICROSCOPIC FUNGI. examining many of them in different states, I at length found a small maggot in some of the younger spots, so that the globules are probably its excrement, and the fibres, the woody fibres of the plant unfit for its food.” We now-a-days smile at such simple and singular conjectures. It affords evidence of the manner in which the speculations of one generation become follies in the next. Only two species of cluster-cups are described in Withering’s Flora under the genus Lycoperdon: one of these is now called Acidiwm compositarum, and is found on various composite plants ; the other includes the species found on the wood-anemone and that on the moschatel, and also probably a species of Puccinia on the wood-betony. To render this chapter more complete, though of less importance to the microscopist, we may allude to the other two genera comprised within this order. Peridermium is the name of one genus which contains three British species found on the leaves and young shoots of coniferous trees. In this genus the peridium bursts irregularly, and does not form cups, or horns, or fringed vessels. The most common species is found on the needle-shaped leaves of the Scotch fir (plate IT. fig. 27), and also on the young twigs, in the latter instance larger and more prominent than in the former. The elongated peridia burst irregularly at their apicer without forming teeth (fig. 28). In the genus Hndophyllum, as its name implies, CLUSTER-CUPS. 21 the peridium is imbedded within the substance of the succulent leaves. The only species we possess is found rarely upon the common house- leek. We have derived much pleasure in viewing the astonishment and delight exhibited by friends to whom we have personally communicated specimens of the little fungi we have enumerated for examina- tion under the microscope; and we recommend with confidence this group of parasitic plants, unfortunately so little known, as well worthy of the attention of all who are interested in the minute aspects of nature, and who can recognize the hand— “That sets a sun amidst the firmament. Or moulds a dew-drop, and lights up its gem.” Note.—For details of the supposed relationship of species of Restelia to species of Podisoma, we must refer to a paper published in the Journal of the Quekett Microscopical Club for 1871; and for other instances of “ Polymorphism,” to an article in the “Popular Science Review” for January, 1871. MICROSCOPIC FUNGI. CHAPTER IL SPERMOGONES. N addition to their spore-bearing spots, lichens have for some time been known to possess other organs, termed spermogones, which are probably concerned more or less in the reproductive pro- cess. The first intimation of the existence of similar bodies in the entophytal fungi originated with M. Unger in 1833, but it was left to Dr. de Bary and the Messrs. Tulasne, twenty years later, to examine and determine satisfactorily the nature ‘and value of the spermogones of the Uredines. It was at first believed that the smaller pustules— which sometimes’ precede, and sometimes accom- pany, the cluster-cups and some other allied fungi —were distinct species developed simultaneously therewith, or members of a new genus, which, under the name of Acidiolum exanthematum, found a place in the mycologic system. Without staying to trace the stages through which the elucidation of their true nature pro- ceeded, it will suffice for our purpose to tell what is now known of these secondary organs ; to accomplish which we must stand greatly indebted to the independent researches of Messrs. de Bary and Tulasne. It has been demonstrated that both these bodies, namely, the primary organs or cluster- ” SPERMOGONES. 2g cups, and the secondary organs or spermogones, are developed from the same mycelium; but the value of the latter is still undetermined. If they possess ‘any fecundative power, the process has not been traced; or if they are in themselves repro- ductive, they have not at present been seen to germinate. Their uses, therefore, in the economy of the parasitic plant of which they are now known to form a part is still a mystery, and they remain valueless in the determination of genera and species. Any speculation which might regard them as male organs would be premature, and without support in fact. Hitherto only some species of the genera described in the foregoing chapter, and others belonging to genera not hitherto named, have been ascertained to possess spermogones. Of the former are the Restelic, some species of Afcidiwm, as those of Huphorbia, &c., and Peridermium Pini. These spermogones are of a very simple struc- ture—very delicate, indeed; so much so, that they will scarcely bear preparation for demonstration. De Bary states that they originate from plain, delicate, inarticulate threads, about half the thick- ness of the mycelium (the root-like branching ‘fibres which form the fundamental stratum of fungoid growths), which are developed in large quantities, and closely packed together. These threads are compacted together so as to form an outer enveloping integument or peridium, which is 24 MICROSCOPIC FUNGI. either globular or hemispherical (or in some in- stances elongated), more or less immersed, and at length opening at the apex (fig. 153) by a regu- larly formed minute ostiolum. The inner wall of the peridium is covered with a thick forest of simple filaments standing on end. From the summit of these filaments or sterigmata, the spermatia are borne. These are either isolated or associated together in strings or chaplets, are exceedingly minute, of an ovoid or oblong shape, and are produced in such numbers as to fill the cavity of the spermogone. Besides these, a viscid fluid is secreted, in which the spermatia are im- mersed, and which is expelled with them from the orifice of the peridium. According to the density of this fluid, or the hygrometric state of the atmo- sphere, it appears sometimes in drops, and some- times oozing out in threads or cirrhi from the spermogones. To compare minute things with gigantic, as a recent author has observed, it resembles the lava issuing from the crater of a volcano. The colour of this spermatiferous matter is commonly orange, but in some instances brown, though not constantly of the same colour as the spores produced from the same mycelium. This gelatinous substance is dissolved away from the granular bodies which are immersed in it, by adding a little water upon the slide on which the mass is placed for examination. The granules, or spermatia, then exhibit those peculiar movements SPERMOGONES. 25 which have been observed in the similar bodies in lichens, and fitly described as “a sort of oscillating motion, as of a body attached at one extremity.” The cause of this motion is at present uncertain, vibratile cilie, to which similar movements are referred, being altogether absent; but probably, as De Bary believes, the cause may be found in the influence of exosmose. The largest spermatia yet examined (those of Peridermium Pini) have a length equal to zeyq of an inch, but their width seldom exceeds z;25g5 of an inch, whilst in others their length does not exceed the width of those just named. Messrs. Tulasne affirm that all these corpuscles, as well as the mucilaginous fluid, evolve an appre- ciable odour, resembling that of the pollen of the willow. M. Léveillé compares the odour to that of orange flowers, and M. de Bary to that of the evening primrose. The spermogones do not always appear like pustules on the surface of the leaves, for some- times their presence is only indicated by minute depressed punctures which are scarcely visible; generally, however, they may be recognized by an obtuse, or otherwise a pointed, protuberance that surmounts them. The margin of the orifice is sometimes furnished with short hairs, but is more frequently ornamented with a pencil of long hairs, which are stiff and erect, and of the colour of the enclosed spermatia. 26 MICROSCOPIC FUNGI. In many of the species of Acidiwm the cups are disposed in a more or less regular circle, the centre of which is occupied by a group of spermogones; at the same time, the corresponding spot on the opposite surface of the leaf will frequently be found also occupied by other spermogones—in some instances in greater number than on the same surface of the leaf on which the cups are seated. This is the case in the Meidiwm which is found upon the leaves of the coltsfoot, and that of the honeysuckle. Very bright orange-coloured spots may be ob- served in autumn (we have encountered them often in August and September) upon the leaves of pear trees, and which are covered with little tubercles, at first of the same colour, but ultimately becoming brown. These pustules are so many spermogones belonging to Reestelia cancellata, a kind of cluster- cup found in the same localities. These spots have long since been noticed, and regarded as connected with the Restelia, but in what manner has until recently been unknown. The Rev. M. J. Berkeley noticed them in the English Flora in 1836, or at least the granulations on the upper surfaces of the leaves bearing FR. cancellata, BR. cornuta, and RK. lacerata, and called them abortive pseudoperidia. Before this (in 1804) they had been observed by Rebentisch. An examination of one of these spots under a low power of the microscope, and afterwards a section of one or more of the pustules, cut with a sharp razor, and viewed with a higher power, will give an SPERMOGONES, Fia. 1.—Acidium grossularie. e¢. Cluster-cups. s, Spermogones. », 2—Section of ripe spermogones of Aeidium Euphorbia. 27 a. Spermatia. a. Sterigmata bearing spermatia (De Bary). SPERMOGONES. 29 idea of the nature of the bodies we are attempting to describe. During the past summer we have noticed very similar orange spots on leaves of the berberry containing spermogones on both surfaces, and these appeared before any cups had been found on that plant. In this instance no cups were pro- duced from the spots on the leaves examined, and which were carefully noticed at intervals until they withered and fell. In some instances, as in Restelia cornuta, which is found on the leaves of the mountain-ash, the cups are produced on the lower, but the spermo- gones almost exclusively on the upper surface. The spermogones of Peridermium Pini are white, few in number, and are developed, not only in the spring, but sometimes reappear in the autumn upon the same leaves that produced them at the com- mencement of the year. In such instances as those of the Acidiwm of the spurge, and also the goatsbeard, in which the cluster-cups are arranged in no appreciable order, the spermogones are scattered amongst them, and even in some instances appear on different leaves. The spermogones are common on the wood spurge in spring, scattered over both surfaces of the leaves before the cluster-cups make their appearance, and gradually these latter are developed amongst them, commencing from the apex of the leaves and pro- ceeding in the order of their development towards the base. In this instance the spermogones are 30 MICROSCOPIC FUNGI. bright yellow, as are afterwards the cups and spores of the Heidiwm. In most instances the appearance of the spermogones precedes that of the sporiferous organs, but the latter follow sufficiently speedy for perfect development before the decadence of the spermogones takes place. After the expulsion of the spermatia and the fluid which accompanies them, the whole mass dries up; and where many spermogones have been clustered together in the same spot a brown homogenous crust is formed upon the epidermis ; where they are produced singly, a brownish incrustation is visible about the mouth of each spermogone. Re-agents applied to the spermogones whilst in full vitality indicate the presence of a considerable amount of a protein substance, which, with sugar and sulphuric acid, produces a deep purple red colour. From what we have already stated of the method of occurrence of these organs, the following is the only order, apparently, preserved in their develop- ment, although no definite rules can at present be affirmed. The spore spots of cluster-cups are generally found upon the under surfaces of the leaves on which they are produced, and the spermo- gones are most numerous on the upper. When both the cluster-cups and the spermogones appear in the same group on the same surface, the sper- mogones commonly occupy the centre, and the cups are arranged in a circular manner about them. In other, and fewer instances, both Pate taiet SPERMOGONES. 3l organs stand together indiscriminately upon the same surface. The spermogones are also developed centri- fugally, at least so far as at present observed, for when they are produced in a cluster the central one first opens and discharges its contents, and thus the development proceeds outwards from the centre to the circumference. When the spermogones are scattered, as in those of Huphorbia, they are first observed at the apex of the leaf, whence they are developed in succession towards the base. The latter should be sought for on the young plants of the wood-spurge in March or April, at which time we have found them abundant at Darenth wood, near Dartford. It must not be concluded, from the fact that we have not yet adverted to spermogones in connection with other fungi, that they are peculiar to the Aicidiacet. Such is by no means the case. As we have hereafter described other genera and species in which spermogones occur, it would be out of place to enter upon further details here. Let it suffice therefore that we state that they have been found in members of the genera, Aregma, Triphrag- anum, Puccina, Lecythea, Trichobasis, and Uredo, but they have been found much more generally in Restelia and Metdiwm than in any other genus. As comparatively little is yet known of these bodies, a fair field is open to the enterprising microscopist, with time at his disposal, and a good 82 MICROSCOPIC FUNGI. store of perseverance, to win for himself renown in the discovery of fresh facts, and the elucidation of some of the mysteries which yet enshroud these interesting organisms. From the foregoing pages he will learn the direction in which his researches should tend, and he may be assured that every new ‘fact is of importance when carefully ascertained. Note.—For observations on the Spermatia of Fungi, see communication by Dr. Max Cornu, translated in “ Grevillea” for June, 1877. DI-MORPHISM. 33 CHAPTER III. DI-MORPHISM. EFORE entering further and more fully upon the subject of this volume, it may be advisable to attempt an explanation of a phenomenon of no uncommon occurrence in many groups of Fungi, and which is termed di-morphisin. In the Uredines, or uredo-like fungi, as well as other of the Coniomycetes (in which the spores are the principal feature), the same fungus appears under two or more distinct forms, not necessarily mere differences of age, but so distinct that they have been regarded (and some are so still) as different species belonging to different genera, often far removed from each other, and bearing different names. One plant, for instance, sprinkled over the under surface of a rose-leaf, ike turmeric powder, has its mycelium, or root-like threads, penetrating the tissue, whilst bearing above its spherical golden-coloured spores. Its vegetative system is complete, and, apparently, its reproduc- tive also; hence it seems to claim recognition as a perfect plant, and under the name of Uredo Rose was so recognized, until microscopical investigation determined otherwise. Thus it has been discovered that certain dark brown spots which appear later v 34 MICROSCOPIC FUNGI. in the season are produced upon the same mycelium, and are indeed aggregations of more perfect and complex fruits of the same plant. Before this point was satisfactorily decided, the brown spores, which are borne on long stalks, and are themselves septate or divided (apparently or really) by trans- verse partitions into a complex fruit, received the name of Puccinia Rose. At this period, Uredo Rose and Puceinia Rose, or the yellow fungus and the dark brown fungus, were believed to be dis- tinct and different plants; now, on the contrary, they are believed to be different forms of fruit produced by the same plant; i.e, an instance of di-morphism. Aregma muwcronatum, Fr., is the present scientific name of what is regarded as the perfect fungus, whilst the uredo-form either beary the name of Lecythea Rose, Lev., or by some mycologists is rejected altogether as a spurious species. During the summer it is not uncommon to find the leaves of some grasses, of the hop, of roses, and many other plants, covered with a kind of white mould, which appears under the microscope as a multitude of small transparent colourless cellules, generally attached to each other in a moniliform or beaded manner. These moulds were long known under the generic name of Oidiwm, to which genus the vine disease was also referred. More minute investigation and more careful examination proved that these moulds were not in DI-MORPHISM. 85 themselves perfect plants, but merely conditions of other fungi of a higher order, little differing it is true in external appearance to the naked eye, but offering material differences in structure under the microscope. Upon the white mould-like threads, spherical bodies are produced in the autumn, con- taining little sacs or asci filled with spores; and in this condition the plants are arranged under the genus Hrysiphe, whilst the species of Oidiwm which represented their imperfect condition, are excluded from the system. Here, again, we have examples of di-morphism. In the Journal of the Microscopical Society, Mr. F. Currey has detailed several instances of di- morphism which have fallen within his experience. In one instance he has shown that a small simple spored fungus, termed Cryptosporium Nees, Ca., is only a state or condition of a fungus with com- pound fruit, belonging to the Spheria section of ascigerous fungi, called Valsa suffusa, Fr. Both plants are exactly alike externally, but the peri- thecium, or flask-like receptacle containing the fructification, in one instance only holds naked spores, and in the other the spores are contained in little elongated vesicular bags or asci, which are packed within the perithecium. Whilst writing this, one of the most wonderful books in a book-producing age lies beside us; it is the second volume of a work on fungi, by the brothers Tulasne ; and this, as well as its prede- d2 36 MICROSCOPIC FUNGI. cessor, is devoted to this very subject of a multi- plicity of form in the fructification of these plants. Illustrated by the most exquisite of engravings which art has ever produced, it also unfolds many a page in the history of these organisms, for which mycologists were not altogether unprepared. In noticing this work, one of our most eminent authors on mycological subjects quotes as an example Dothidea ribis, Fr., one of our most common fungi, which occurs in the form of little black shields on dead twigs of currants and goose- berries. Here we have, he says, naked spores (conidia) growing on the external cells of the stroma; we have naked spores of a second kind (stylospores) produced in distinct cysts (pyenides) ; we have minute bodies of a third kind (spermatia) produced again in distinct cysts, resembling very closely similar bodies in lichens; and we have a third kind of cysts, containing the usual sporidia in sausage-shaped hyaline sacs (asct). Hven here, however, we have not done with marvels; for if the stylospores are placed in water, they produce in the course of twenty-four hours conidia of a second order, exactly analogous to those which arise on the germination of the spores of the rusts and mildews which affect our cereals and other plants. Further reference is also made to three species of moulds, which M. Tulasne has shown to be only varied forms of the mycelium of a species of DI-MORPHISM. 87 Spheria common to various plants; these moulds having been hitherto regarded as fungi perfect in themselves. In the Uredines, to which much of this volume is devoted, the genera known as Lecythea and Trichobasis are by some mycologists excluded altogether, as containing only species which are mere forms of more highly-developed uredines, such as Puccinia, Aregma, and others. On the other hand, they are retained by those who possess a lingering doubt whether both forms may not be distinct, though developed from the same pustule. As the two forms are distinct in appearance, it will better answer our present purpose to treat them separately, notwithstanding the belief that, in a scientific point of view, the evidence is all in favour of their union. In fungi of this kind the mycelium, or delicate root-like threads, consists of thin filaments, which are spread through all parts of the plant occupied by the parasite, traversing the intercellular pas- sages, but rarely perforating and entering the cells. This compacted and interwoven mycelium forms a kind of cushion beneath each pustule, on which the fruits of the parasite rest. By the increase of this cushion and the swelling of the fruit, the epidermis which covers them is distended, and ultimately ruptured, so that, when ripened, the spores escape. It must be remembered that the fruit is of from two to four kinds. Small bodies, called spermatia, 38 MICROSCOPIC FUNGI. which are derived from the spermogones, and which have not yet been known to germinate; Stylospores, produced either singly, or in bead-like, or moniliform, strings, and which either precede or are associated with the true spores; Spores, some- times simple, but often complex; and Sporidia, or secondary sporules, which are produced on the germinating threads of the true spores. The various genera of these endophytes owe their distinctions to the form, or mode of develop- ment of their true spores. In one instance these spores are united in pairs, or divided by a septum, so that they are two-celled: these are named Puc- cinta. In another instance the spores are one- celled, and at first borne upon a stalk or peduncle, from which they are detached in ripening: such are called Trichobasis. It is unnecessary here to indicate all the variations to illustrate the fact that the generic distinctions are based upon the cha- racters of the true spores. How unsatisfactory such a mode will appear, when subjected to expe- rience day by day, a botanist would suspect. In the same pustule, resting upon the same cushion of mycelium, the spores of an Aregma will be found with those of a Lecythea, and those of a Puccima with Trichobasis. More than this has even been affirmed. The alternation of generations, known to students in the animal world, is here repeated in the vegetable. Dr. de Bary declares that certain data appear to indicate that Mcidiwm constitutes DI-MORPHISM. 39 not a genus by itself, but are organs in the develop- ment of some other germs and species, possessing its spermogonia, its Afcidiwm, its Uredo, and its spores, properly speaking ; whilst in others the Uredo-form, the Puccinia-form, and the Aicidiwm- form may alternate. It is not our intention to enter deeply upon the discussion of this subject, of so little interest to the beginner, and so out of place in an introduction to the study. That forms and conditions are multifarious, and that an entire revision of the classification is inevitable, are facts which do not require many words to establish. Already it is to be feared that in this brief chapter we have said too much, and must recommend its perusal again, when the names and characters of the genera alluded to have been rendered more familiar. It could scarcely have been permitted that the student should go far without being cautioned that there is such a thing as di-morphism in microscopic fungi; and the explanation of such a phenomenon must presuppose a certain amount of knowledge which, thus far, the reader could not have acquired. Hence an anomaly, to escape from which an ulti- mate return to the subject will be necessary. In a recent account of Dr. de Bary’s experi- ments,* an interesting history is given of the development of a rust-like fungus, which is common * De Bary—“ Annales des Sciences Ne.turelles,” ser. 4, vol. xx. 40 MICROSCOPIC FUNGI. on many plants of the pea and bean tribe. As it may serve to illustrate some of the preceding, as well as subsequent, remarks on development, an abstract shall close this chapter. The spores of this species (Uromyces appendi- culatus) are oboval cells, terminated by a rounded point, provided with a deep brown, smooth, epi- spore, or outer coating, and a distinct, but colour- less endospore, or inner coating. These enclose a granular matter, which surrounds what has been termed the nucleus, but which appears to be a vacuole. At the top of the epispore is a pore which is characteristic of the genus. The spores are supported on a colourless, or slightly-tinted pedicel of considerable length (plate VII. fig. 150). By means of this pedicel, the spores are attached to the fostering plant, on which they form pustules or sori of a blackish colour, and variable extent. These spores are ripened towards the end of summer or beginning of autumn. During winter they remain in a state of repose, but in the follow- ing spring the faculty of germination developes itself. At this period, when moistened or placed ona humid soil, they germinate at the end of a few days. The spore then emits a curved and obtuse tube, which soon ceasing to elongate itself, gives origin to three or four sporidia, of a reniform or kidney shape. When cultivated on moistened glass, these sporidia also emit a short, thin, slender tube, which produce in turn secondary DI-MORPHISM. 4) sporidia. Here vegetation ends in the artificial culture above indicated. When the sporidia are sown upon the epidermis of a favourable plant, the germ-tube being emitted, penetrates the wall of any approximate cellule, swells and increases into a cylindrical tube equal in thickness to the original sporidia, and therefore four or five times the diameter of the germ-tube before it entered the cellule. The contents of the sporidia and external portion of its germ-tube pass into the portion within the cellule, and then these external portions perish, and all evidence of the entry is obliterated, except a very minute point at which the tube remains attached to the inner sur- face of the wall of the cellule. The enclosed tube soon elongates, divides, and becomes branched. These branches perforate the inner walls of the epidermis, and pass into the intercellular spaces of the parenchyma to become mycelium. This takes place within 24 hours. A few days afterwards the mycelium is spread through the parenchyma. At length the surface of the same spots which had been sown in the first instance with the sporidia, become of a whitish tint, rapidly increasing and intensifying. Three days after, little protuberances appear on the surface of the white spots. These are of an orange colour, and many of them are surmounted by a little drop of mucilaginous fluid. These are spermogones. Their number daily in- creases, and a little time after appear numerous large 42 MICROSCOPIC FUNGI. globular protuberances intermingled with them. These soon rupture the epidermis, and take the orange colour and cylindrical form of cluster-cups (Aicidium). At length the summit of the peridia opens to allow the escape of the stylospores. It is easy to assure oneself that the spermogones and cluster-cups proceed from the mycelium of the sporidia which had been sown. During several days the length and number of the peridia of the Atcidium continue to increase. One month after sowing, brownish or blackish points make their appearance upon the whitish spots, around, or intermingled with the cluster-cups. These increase rapidly in number and magnitude. Examined by the microscope, they present the ordinary fructi- fication of Uromyces, mingled with stylospores. Thus the mycelium of the cluster-cups engenders at the end of its vegetation fruits equal in all points to those from whence they are in the first instance derived. The stylospores of the cluster-cups possess the irregular, globular form and structure of their congeners. They are filled with orange granular matter, and provided with a colourless, finely- punctated epispore. When these stylospores are sown on the moistened epidermis of a favourable plant, the germ-tube at first creeps along the surface, but as soon as its extremities find a stomate, it enters it and elongates itself in the air-cavity below the orifice, receives the contents of the original DI-MORPHISM. 43 stylospore and exposed portion of its tube, then separates itself from those parts, which become dispersed. The active part increases and ramifies, and produces a mycelium which spreads through the intercellular passages of the parenchyma. At the end of from six to eight days, the whitish spots appear on the surface of the fostering plant, and indicate that the fructification of the parasite is about to commence. The epidermis is elevated and broken, and little brown pustules appear through the openings. These are the stylospores of Uredo, which are produced in immense quan- tities, and soon cover the pustules with a deep brown dust. Later, the formation of the stylo- spores is arrested, and the true germinating spores appear in the same pustules. The stylospores of Uredo are borne singly at the top of short filaments. On arriving at maturity they detach themselves. They are of a globular form, with a reddish brown epispore, provided with little pointed prominences, and three pores at equal distances. After maturity they germinate in pre- cisely the same manner as the stylospores of the cluster-cups. They enter only through the stomata of the epidermis. The pulvinules are identical with those which the stylospores of Afcidium originate, and they also produce true spores at the end of their vegetation. No other fruit arises from them. These organs, therefore, always reproduce the same form to which they owe their origin. 44 MICROSCOPIC FUNGI. The result of these investigations shows that the bean-rust (Uromyces appendiculatus), besides sper- mogones, possesses four sorts of reproductive or- gans, which all serve to propagate the species, but that one alone of them produces it in a form alrays identical, whilst the others present well-marked alternations of generation. Hence it is concluded that there are, I. Spores which produce in germinating the pro- mycelium, and II. Sporidia.—These give place to a mycelium, which bears afterwards— Il. Acidiwm.—Particular organs which engen- der stylospores, and which produce— IV. Uredo, the second form of the stylospores, and later, spores (No. I.), which are always asso- ciated with Uredo in the same pustule. The spores and stylospores of Uredo come also upon the old mycelium, which has previously produced Aicidium. The Uredo stylospores always produce Uredo, and true sporea, MILDEW AND BRAND. 45 CHAPTER IV. MILDEW AND BRAND. R. WITHERING’S “ Arrangement of British Plants” in 1818 reached its sixth edition. This is little over half a century ago, and yet the whole number of species of Fungi described in that edition was only 564, of which three hundred were included under the old genus Agaricus. Less than eighty of the more minute species of Fungi, but few of which deserve the name of microscopic, were supposed to contain all then known of these wonderful organ- isms. Since that period, microscopes have be- come very different instruments, and one result has been the increase of Withering’s 564 species of British Fungi to the 2,800 enumerated in the “Han book of British Fungi.’ By far the greater number of species thus added depend for their specific, and often generic characters, upon microscopical examination. The proportion which the cryptogamic section bears to the phanerogamic in our local Floras before 1818, now almost invol- untarily causes a smile. Even such authors as were supposed to pay the greatest possible respect to the lower orders of plants could never present an equal number of pages devoted to them, as to the higher orders. Relhan, for instance, only occupies one- 46 MICROSCOPIC FUNGI. fifth of his “Flora Cantabrigensis,” and Mudson one-fourth of his “ Flora Anglica,” with the Cryp- togamia. At the present time, it will be seen that, with a liberal allowance for “ hair-splitting,” the number of British species of flowering plants scarcely more than equals the number of Fungi alone, not to mention ferns, mosses, alge, and lichens ; and we lately had no “ Flora”? which con- tained them, and but a minority of our botanists know anything about them. If we need excuse for directing attention to some of the most interesting of these plants, let the above remarks suffice in lieu of formal apology. “ Mildew”? is just one of those loose terms which represent no definite idea, or a very different one to different individuals. Talk of mildew to a farmer, and instantly he scampers mentally over his fields of standing corn in search of the brown lines or irregular spots which indicate the unwel- come presence of Puccinia graminis, known to him, and to generations of farmers before him, as “ mil- dew.” Try to convince a Norfolk farmer that any- thing else is “ mildew,” and he will consider you insane for your pains. Speak of mildew in your own domestic circle, and inquire of wives, or daughters, or servants, what it means, and without hesitation another, and even more minute species of fungus, which attacks damp linen, will be indi- cated as the true mildew, to the exclusion of all others; and with equal claims to antiquity. Go to MILDEW AND RRAND. 47 Farnham, or any other hop-growing district, and repeat there your question,—What is mildew ?— and there is every probability that you will be told that it is a kind of mould which attacks the hop plant, but which differs as much from both the mildew of the farmer and the laundry-maid as they differ from each other. The vine-grower has his mildew, the gardener his mildewed onions, the stationer his mildewed paper from damp cellars, the plasterer his mildewed walls, and in almost every calling, or sphere in life, wherever a minute fungus commits its ravages upon stock, crop, or chattels, to that individual owner it becomes a bug- bear under the name of “mildew.” Reluctantly this vague term has been employed as a portion of the title to this chapter, but it must be limited in its application to the “ mildew of corn,” known to botanists as Puccinia graminis, and not to include the numerous other microscopic Fungi to which the name of mildew is often applied. The origin of this term and its true application may undoubtedly be traced to mehl-thau, “ meal dew.”