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found. This may not, however, have been the case with all double-holed bullåns, as in some cases the holes are of nearly equal depths and of different shapes. Near Killgoola, west of the lower portion of Lough Corrib, are a pair of small bullāns cut in the solid rock, of nearly equal size, and called Gluine Phaudrick (Anglice, Patrick's Knees), as the saint is said to have worn them praying. Their original use seems very obscure. The word bullān properly means any conical substance, or a circular excavation ; thus water-worn holes in rocks are called bullāns, also a cow's teats; both from their shape and aperture. In olden times baptismal fonts, from

Fig. 156. Section of the Bullān near Lough Gur, co. Limerick.

being circular excavations in stones, may have been so called, but they are called in modern Irish Umarbaisdidh, or baptismal troughs. To us it would seem probable that the bullāns at the churches may have been put to more than one use, sometimes being used as fonts, at other times as corn-crushers, or even for grinding up the herbs, &c., used for the distillation of the drinks of the period. The latter suggestion would specially refer to the five-holed bullän, called Leac-na-poul, or the holed flag, at Cong (fig. 157), as it was in the vicinity of a large abbey, a place where probably there was a large consumption. Those also in such localities as the mountains near Adrigole, Tulla, &c., may have been used for bruising the heather for the manufacture of the ale about which we hear. Unfortunately the process is now unknown; but that the heather was once valuable seems probable, as otherwise we would not find the remains of the walls and fences dividing up the wild heathery mountains into small lots. From bullāns we maturally go to the holy wells, as many of the former are thus designated. These wells are dedicated to different saints, although probably they were a pagan custom that was engrafted on to the Christian religion. At various times the priests of the different forms of Christianity have tried to do away with them, but without success, and at the present day they are much venerated and visited. Without doubt they are efficient in some diseases, such as sore eyes; this, however, is just as probably due to the regular

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the editors of the Journal of Horticulture at the beginning of June, and my reply to the correspondent was printed on June 10th. The leaves were badly diseased, and I detected the Peronospora in very small quantities here and there, emerging from the breathing pores. This was a week or ten days before Mr. Berkeley brought the matter before the Scientific Committee of thc Royal Horticultural Society; and when I heard Mr. Berkeley’s remarks about the Protomyces, I immediately accused myself of great carelessness in possibly overlooking it; but I was equally certain of the presence of the Peronospora in the specimens I examined. On receiving authentic specimens of diseased plants from Mr. Barron, of Chiswick, the brown spots on the potato leaves at once reminded me of the figures of some species of Protomyces, and the dimensions agreed tolerably well with some described plants of that genus; but the spots, when seen under a high power, appeared very unlike any fungus, and they were very sparingly mixed with other bodies much smaller in diameter, and with a greater external resemblance to true fungus spores. These latter spore-like bodies were of two sizes—one transparent and of exactly the same size as the cells of the leaf (and therefore very casily overlooked), and the other darker, possibly reticulated, and smaller. A few mycelial threads might be seen winding amongst the cellular tissue, and these threads led me to the conclusion that the thickened and discoloured spots on the leaves were caused by the corrosive action of the mycelium, in the same way as peach, almond, walnut, and other leaves are thickened, blistered, and discoloured by the spawn of the Ascomyces, as illustrated at the last meeting of the Royal Horticultural Society. My opinion, therefore, was soon formed that the “new” potato disease (as it has been called) was no other than the old enemy in disguise, or, in other words, that it was the old Peronospora infestaus in an unusual and excited condition. That climatic conditions had thrown the growth of this fungus forward and out of season was probable; but the idea that the pest would not at length attack all and every sort of potato was to me most unreasonable, though the more tender sorts might be the first to suffer. Suspecting the two-sized small bodies before mentioned to be of the nature of spores, and remembering my experiments during last autumn with ketchup, in which I observed that the spores of the common mushroom might be boiled several times, and for lengthened periods, without their collapsing or bursting, I thought I would try to set free the presumed spores in the potato leaves by macerating the foliage, stems, and tubers in cold water. This maceration was necessary because the tissue of the diseased leaves was so opaque and corroded, and the cell-walls were so thickened, that it was difficult to distinguish the threads and suspected spores from the cellular tissue. I did not treat the leaves with boiling water because I wished to keep the threads and spores alive. From day to day I kept the diseased leaves, stems, and tubers wet between pieces of very wet calico, in plates under glass, and I immediately noticed that the continued moisture greatly excited the growth of the mycelial threads; this to me was quite unexpected, as I had merely wished to set the spore-like bodies free. So rapid was now the growth of this mycelium, that after a week had elapsed, some decayed parts of the lamina of the leaf were traversed in every direction by the spawn. Thinking the close observation of this mycelium in the now thoroughly rotten and decomposed leaves might end in some addition to our knowledge of Peronospora infestans, to which fungus I had no doubt from the beginning that the threads belonged, I kept it under close observation, and in about ten days the mycelium produced a tolerably abundant crop, especially in the diseased tubers of the twosized bodies I had previously seen and measured in the fresh leaves. The reason why these objects, which undoubtedly occur in and about the spots, are so extremely few in number in those positions is, I imagine, because they require a different set of conditions for their normal growth, and these conditions are found in abundant and continued moisture. The larger of these bodies I am disposed to consider the “oogonium ” of the potato fungus, and the smaller bodies I look upon as the “antheridia” of the same fungus, which are often terminal in position. The filaments of the latter are commonly septate, and sometimes more or less moniliform or necklace-like. Both oogonium and antheridium are very similar in nature and size to those described as belonging to Peronospora alsinearum and P. umbelliferarum ; and this is another reason (beyond my seeing undoubted P. infestans on potato leaves at the beginning of June) why I am disposed to look upon these bodies as the oogonium and antheridium of the potato fungus. The larger bodies are at first transparent, thin, pale brown, furnished with a thick, dark, outer wall, and filled with granules; at length a number (usually three) of vacuities or nuclei appear. The smaller bodies are darker in colour, and the external coat is apparently marked with a few reticulations, possibly owing to the collapse of the outer wall. I have observed the two bodies in contact in several instances. After fertilization has taken place, the outer coat of the oospore enlarges, and soon gets accidentally washed off in water. Both antheridium and oogonium are so slightly articulated to the

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threads on which they are borne that they are

detached by the slightest touch, but with a little care it is not really difficult to see both bodies in situ; and

my observations lead me to think that conjugation frequently takes place after both organs are quite free. The antheridia and oogonia are best seen in the wettest and most thoroughly decomposed portions of the tissue of the decomposing tuber, but they occur also in both the stem and leaf. I consider Mr. Alexander Dean’s remark, as reported in the Gardeners’ Chronicle for June 19th last, p. 795, to have a distinct bearing on this point, where he says, “In all cases where the seed tubers were cut they were quite rotten.” Before I referred to De Bary’s measurements of similar organs in other species of Peronospora, I was disappointed with the results of my observations, and felt disposed to refer the bodies and threads in the potato leaves to Saprolegnia; but a glance at the figures now published and the similar figures copied from De Bary to the same scale, will show that if the bodies observed by me are Saprolegnia-like, the oogonia and antheridia figured by De Bary show an exactly similar alliance. Still, as the Saprolegnieae are at present defined, I am by no means inclined to describe the bodies observed by me as really belonging to that tribe of plants. The Saprolegnieae have the habit of moulds and the fructification of algae, and they live on organic matter, animal and vegetable, in a state of putrefaction in water. One of the best known of these plants is Botrytis Bassiana, the parasite which causes the disease of silkworms. Now the genus Botrytis among fungi is almost or quite the same with Peronospora, to which the potato disease belongs; and I consider it a strong argument in favour of my Saprolegnia-like bodies being the oogonia and antheridia of the Peronospora when such an authority as Mr. Berkeley considers one of the Saprolegnieae (Achlya) “may be an aquatic form of Botrytis Bassiana”—the silkworm disease. The common fungus which attacks flies (so frequently seen on our window-panes in autumn), Sporendonema muscae, Fr., is said to be a terrestrial condition of Saprolegnia ferax, Kutz., which latter

only grows in water; and if a fly infected with the

fungus be submerged, the growth of the Saprolegnia is the result. # It would now seem to be somewhat the same with the potato when diseased, in the fact that when submerged a second form of fruit is produced. Between the two moulds, Botrytis and Peronospora, there is little or mo difference; the characters of Corda, founded upon the continuous or septate filaments, cannot be relied upon, and even De Bary himself figures P. infestans with septate filaments, like a true Botrytis. The intimate connection, however, between the Saprolegnieae and some moulds cannot be denied, as the instances above cited clearly show; and I am therefore disposed to think that the fungus which produces the potato disease

is aquatic in one stage of its existence, and in that stage the resting spores are formed. Reference may here be made to the bodies found germinating in the intercellular passages of spent potatoes by Dr. Montagne (Artotrogus), and referred by Mr. Berkeley to the Sepedoniei. Ever since Mr. Berkeley first saw these bodies he has had an unswerving faith in the probability of their being the secondary form of fruit of Peronospora infestans, but unfortunately, as far as I know, no one has ever found a specimen of Artotrogus since Montagne. The question may, therefore, be naturally asked,— How does Artotrogus agree with the presumed resting spores here figured and described ? And has Mr. Berkeley been right or wrong in clinging so tenaciously to his first idea? Fortunately for the investigation of the potato disease (which can never be cured till it is understood), Mr. Berkeley has given in the Journal of the Royal Horticultural

...A.Soci&#y the number of diameters his figures are

magnified to, and I have here engraved those figures so as to correspond in scale with my own drawings, which latter are sketched with a camera lucida. It will be seen that they are the same with each other both in size and habit, with the exception of the processes on the mature spore of Artotrogus— which processes may possibly be mere mycelial threads, or due to the collapsing of the inflated epispore. The reason why these resting spores have evaded previous search is that no one has thought of finding them amongst leaves which had been macerated for a long period in water. There is, however, nothing unreasonable in fruit being perfected in water or very damp places, as it is common in the Saprolegnieae and amongst Algae in general. To sum up, there are four reasons why the bodies here described belong to the old potato disease:– 1. Because they are found associated with the Peronospora and upon the potato plant itself. 2. Because they agree in size and character with the known resting spores of other species of Peronospora. 3. Because some other moulds are aquatic in one stage of their existence. 4. Because they agree in size with Artotrogus. Now that these drawings illustrative of the fungus which causes the potato murrain are reproduced in the following plates, it may be as well to explain at once some of the terms used and the nature and habit of the bodies hereafter referred to, for such readers as may not be thoroughly acquainted with the life history of the destructive parasitic moulds to which the potato fungus belongs. For that purpose reference must be made to fig. 159, which shows (greatly enlarged) a transverse section through the leaf of a potato plant; the two great bodies at A A represent two minute hairs on the leaf, and at B B are seen the individual cells of

which the leaf is constructed. When these hairs and cells are compared with the fine thread at C, which represents a branch of the potato fungus coming out of a breathing pore of the leaf, it will be seen how very minute the fungus is in comparison with the dimensions of the leaf. This fine thread is no other than a continuation of a thread of spawn or mycelium which lives inside and at the expense of the assimilated material of the leaf. When this thread emerges into the air, as here shown, it speedily ramifies in different directions, and bears fruit at the tips of the branches, as at D D; these fruits are termed simple spores, or conidia, because from their smallness they are dust-like. It is quite possible they may be an early state of the vesicles which contain the zoospores, as seen at E, F. However this may be, they are commonly arrested in growth when still small, and they germinate in an exactly similar manner with the zoospores themselves, and may be considered somewhat analogous with seeds. The potato fungus has another method of reproducing itself in the “swarm-spores” shown at E, F. These are so called because, on the application of moisture (as supplied by dew or rain, or when applied artificially), the vesicles set free a swarm of from six to fifteen or sixteen other bodies known as “zoospores,” so named because they are furnished with two lash-like tails, and are capable of moving rapidly about like animalcules. This rapid movement usually lasts for about half an hour, and (like the dust-like conidia or “simple spores” before mentioned) the swarm-spores generally enter the breathing pores of the leaf, and there germinate. So potent, however, are the contents of these bodies when set free, that they are capable of at once corroding, boring, and entering the epidermis of the leaf, or even the stem or tuber itself. These zoospores are best seen when within the vesicle F, where they arise from a differentiation of the contents, but when once set free (G) they are, from the extreme rapidity of their movements, very difficult to make out. In about half an hour they cease to move, their lash-like tails (cilia) disappear, and having burst at one end, a transparent tube is protruded, which is a similar mycelium in every respect with that produced by the simple spore, and which grows, branches, and fruits in a precisely similar manner. Now the great difficulty which has beset botanists for so many years has been to account for the winter life of the potato fungus. Simple spores and zoospores are lost in the production of the mycelium or spawn, and this latter fine thread-like material cannot of course survive the frosts and rains of winter, but must utterly perish with the perished leaves and haulm. A study of other species of Peronospora allied to the one which produces the potato disease, reveals the fact of a third mode of reproduction. Simple spores and zoospores are termed asexual, because they are without sex, as distinguished from other bodies called oospores, which are produced by the contact of two sexual spore - like bodies, known as the antheridium, which is the male, and analogous with the anther, H, and the oogonium, the female, and analogous with the ovary of a flower, J. The oospores, not till now seen for certain in the potato disease, are the true resting spores. Instead of being transparent and unenduring, as are the simple and zoospores, these bodies are at length dense in substance, black-brown in colour, and covered externally with reticulations or warts. They are produced from the mycelium, by the contact of the antheridium and oogonium in the substance of the decaying plant; they are washed into the earth, and there they rest till a certain set of conditions makes them germinate in the year following their production, just as a seed falls and rests in the autumn and starts again into life during the following spring. The terms here used will be better understood if the following note is borne in mind: The oogonium is amalogous with a pod, the oosphere within answers to the ovule, and

the oospore (or resting spore) is the matured seed. The antheridium with its contents is analogous

was ADNAT sc

Fig. 159. Transverse Section of a Fragment of Potato Leaf with Peronospora infectans.

with the anther and its pollen.

In various other fungi nearly allied to the potato

Enlarged 250 diameters.

fungus these resting spores have been seen, measured, and illustrated, but till now the resting spore of the potato fungus has eluded all search. The reason generally given and accepted for its absence

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