Fungus

FUNGUS. To the botanist the fungi are a most interesting class of plants. Their seeds, (spores) and many of the resulting plants are so small that they must be examined with the microscope to bring out their character. What are understood as funguses by the ordinary observer, are toad- stools and Tuff-balls. Smut, mildew and rust are generally termed blight; yet they all belong to the larger class of fungi, the more minute forms below those of mildew, being largely in excess of those larger than mil dew. Fungus, attacks all plants, especially those in a more or less diseased or disorganized condition. Fungus sometimes does attack apparently healthy trees. It attacks all living trees, and also is one of the means of the decom position and decay of dead plants. It is propa gated by spores, minute grains which perform the function of seeds. These, says a writer on fungus life, begin to germinate by sending out numerous filamentous rootlets, composed of a succession of small cells, which perform the office of roots in supporting the plant in an erect position, and supplying it with nourishment. These rootlets are called the mycelium. They also send up stems (mtipes) of various shapes, according to the class to which they belong. The Botryiis infestams, more recently called the Peronospora infestans, is one of the most destruc tive of the fungi that Cause the potato-rot. It had the form of a spreading tree, bearing some three thousand ovoidal spore-cases (acrosporee) on the ends of the branches, somewhat resembling, when taken collectively, clusters of grapes, and hence its generic name Botrytia. The seeds of the fungi, which are contained in the spore-cases, usually have a brown color, like fine dust, and are almost infinite in number. A single plant is said sometimes to produce millions, so small and light as scarcely to be affected by gravity. They cover everything around them—earth, plants, and animals. The air is filled with them, and they wait only for a state of the atmosphere favorable to their growth to seize upon every object within their reach. They live principally upon decaying substances, but the living do not always escape them. The conditions best the potato. Long-continued, warm, damp weather, often causes them to appear in great numbers; but a single day of dry weather will arrest their progress. They mature with won derful rapidity. Puff-balls sometimes grow six inches in diameter in a single night. Certain species have been found growing on the surface of iron that had been heated in the forge only a few hours before. They have also been found growing on the surface of glass. Peronospora infastana matures in a few days, sometimes in fif adapted to their growth sit, first, a debilitated or morbid state of the plant; and, secondly, a proper degree of heat, moisture, and electric influence to induce germination. They do not germinate readily, and the conditions must be very nicely balanced to insure germination at all. They frequently remain inert for a long time, and, when the conditions are complete, fall upon plants like an epidemic, and after a time disap pear almost entirely. Such may, perhaps, some times Mete been the case in their attacks upon teen to eighteen hours even, when conditions are most favorable to its growth, and scatters its seeds by thousands and tens of thousands, to prey, with each successive brood, from to day, upon the expiring plant. The seeds are supposed to enter the pores (stomata) of the leaves and stems, and also to be taken up by the spong.ioles of the roots; and carried along in the circulation of the sap through the plant. The take root in the cellular tissues of the sterns and leaves, stop up the pores with their roots, pia vent the proper elaboration of the crude sap, and exhaust large portions for their own support, besides probably exerting a deleterious chemical influence on the plant. That the seeds of this fungus are capable of destroying the potato has been demonstrated by Dr. DeBary, who mixed some of them in a drop of water and applied them to the leaves and tubers, when brown and livid spots appeared, and afterward decay. All the members of this genus, peronospora, are parasitic on living plants, inducing in them speedy decay, of which they are themselves the cause. To those who wish to study cryptogamic botany, the following from a lecture by Prof. MeNab, delivered in the Royal Agricultural College, England, will be found interesting; The study of the lower order of plants is.attended with many and great difficulties. This is owing chiefly to the minute size of the objects them selves, requiring as they do the microscope for their investigation. Then, again, most of our botanical text-books give only the most superfi cial description of the lower groups, and fix the whole time and attention of the student on the higher or floweringplants. The consequence of this is that the studjr of the higher plants is car ried to such a length in our lectures on bcitany that little or no time is given to the lower orders, a plan of procedure as philosophical as that of teaching zoology merely from the vertebrates and omitting all other divisions. To the more or less flattened or rounded cellular expansion, of these plants, which may consist of only one or of thousands of cells, the term thallus has been applied; and the three groups possessing this may be united, to form a large division of the kingdom, called the Thallvhytes. The thallus may consist of one cell or of many cells; these may be either similar or dissimilar. In some of these Thallophytes we have plants con sisting of one cell, which performs the functions of nutrition during the day, and those of repro duction during the night. In others we have one part of the plant set aside to perform the function of nutrition, while another part per forms the function of multiplication only. In most of the sea-weeds the part of the thallus set apart for the purpose of nutrition is large, while the reproductive organs occupy only a small por tion. In the funguses we have plants which_ obtain most of the nutriment ready made, and, and as.a consequence, an elaborate nutrient sys tem is not required. Hence that portion of the thallus in funguses set aside for the purposes of nutrition, called 'the mycelium or spawn, is com paratively small, while the organs for perform ing the functions of reproduction predominate. The same law holds in the animal kingdom, as in many parasites we have a low type of the nutritive system and a largely developed repro ductive system. In most of the Thaliophytes we have two modes of reproduction, one a true sexual process, in which we have parts equiva lent to the stamens and pistils of the higher plants, while the other is asexual, and therefore to be considered as a process of budding. These two modes of reproduction either alternate or else we may have taking place two or more times in succession before sexual reproduc tion again occurs. This fact is of the greatest importance, and must not be lost sight of. In many of the sea-weeds we have this alternation of sexual generation with budding. At one period in the life-history of the plant true sexual organs may be produced, while at the other periods we have numerous small cells given off, each arme4 with two or more hair-like appendages. As these appendages are capable of moving, they propel the whole mass, to which, on account of its peculiar animal-like motions, the term •zoospore has been applied. The zoospore may therefor be considered as a movable bud of the situp 4 possible construction. The same alternation of sexual generation with budding is to be met with in the funguses„ and the Peronospora affords a very good example of it. Many of our readers must have observed dead flies floating in water in the autumn, with their bodies all covered with fine hair-like threads. This appearance is pro duced by a plant, which was formerly believed to be a sea-weed, but is now placed among the funguses. If we examine the thread with the microscope, we observe a cellular mycelium or nutritive portion of the thallus. At the end of some of the portions of the mycelium we may probably observe a single large cell, the contents of which become broken up into small portions. These small portions of the protoplasm become liberated, and are zoospores or rounded masses of protoplasm, with two hair-like appendages. When free, they are capable of moving about contents of the small male branches, one or more otispores being in this way produced. The olispores are in fact comparable with the fertil ized seed of the higher plants. After a period of rest the otispore germinates and produces a new plant. The reproductive process in the fungus resembles that of many sea-weeds which form otigonia and olispores, the oospores being formed after fertilization from the contents of the for some time, and then growth takes place, and each one will form a new plant; but in another we may observe that the ends of the branches of mycelium form a club-shaped cell. This club shaped body is the female reproductive 'organ, and Is called by botanists otigonium. At each side of this clurb-shaped body two smaller bodies agonium. Then, in the preduction of the moving buds, the zoospores, which multiply the plant asexually, these funguses closely, approach the sea-weeds. The passage from Achyla (the -fungus possesses the sea-weed like character just described) to the fungus producing the potato disease is but a single step. In Peronosparag can be seen, which spring from the same portion of mycelium as the Otigonium, but below it; they are two small branches, which grow upward until they come in -contact with the oligonium, being, in fad, the male reproductive organs, called by botanists antheridia. Inside the agonium are

.be -granular contents, or protoplasm, forming the odsphere. The otisphere is fertilized by the infeafans we have a thallus with the nutritive portion of it, the mycelium, ramifying through the potato-plant. It has also two modes of reproduction, sexual and asexual. In the asex ual form we have a branching tree-like form of the mycelium, making its way through the sto mata or breathing pores of the leaf. Thia branching portion bears rounded swellings., arranged in a somewhat beaded manner, and called conidia. They do not produce zoospores, but develop a mycelium distinctly. Other observers, hoWever, assert that the conidia never produce a mycelium directly, but always from several, in general ten, zoospores. The zoti spores, after moving freely about, attach them selves to the cuticle of the plant, and surround themselves by a delicate wall; they then bore through the outer wall of the epidermic cell, and form a mycelium ramifying through the intercellular spaces of the potato-plant. If the young mycelium is formed in the tuber or potato,' it may remain dormant during the winter, and then spread through the young plant as it grows. The sexual organs of Peromompora develop inside the tissue of the infested plant. The extrem ities of certain of the threads of mycelium form rounded bodies—the otigonia. Inside the ()ago ilia a portion of the protoplasmic contents form the ofisphere. On another branch of mycelium the antheridium is 'produced, which adheres to the wall of the otigonium the contents passing into the oosphere, which is thus fertilized, and the oospore formed. The oospore is surrounded by a thickened skin, wbrch is rough and dark brown in color. After a period of rest, the ferti lized oospore germinates and produces mycelium. The fungus producing the /potato-disease is thus interesting botanically from its peculiar relations to certain of the sea-weeds, in its mode of repro• duction, and in the production of moving zoo spores. From the effect of rain or dew in 'liber ating these zoospores it is not difficult to' under stand how the disease spreads in damp weather. Since it is easier for the unscientific reader to retch ideas by the eye more readily than from e6ientitic descriptions, we give cuts showing adore principal forms of fungi. On page 877 we have illustrated the potato disease or fungi. A disease spot appears in a potato. The micros cope will show the disease commencing where the vascular bundles concentrate. .There the air is in greater volumes than elsewhere, such spots exposed to the causes the blue mold fungus to appear. This however, has no relation to the potato rot. Blue Mold, is Peni cillium glaucum. F, represents the myceliii* or roots, at G, is shown that of potato rot, (Peronospora infestana). The following defini tion is from the report of the Microscopist of the Department of Agriculture at Washington: 2, and 3, 3, potato disease, represent thee com bination of, the spiral and dotted ducts; A, the root stem; new growth or tuber from 1. Viewing, their connection in this way, it will be seen that any germinal disease entering through the root-stem A, will necessarily tiommunicate through all the connecting links, viz., A, 2, 3, 3,1 B. o, o represent the 'rum or a slen der light-colored myceliiim, ,which was found traversing the exterior and interior of the withered potatd stalks. In the more advanced stages the fruit has appendages in length about one and a half times their diam eter. They have a thornlike appear ance, slightly wavy, and of amber -color. To the naked eye they appear like fly-spots, and are very numerous. They appear black, but when treated by nitric acid the dark color is re moved and a cellular structure of an amber color is exhibited. Thus far I have not been able to, detect any sporangia in them. This may be ac counted for from the fact that all the Specimens I have examined had bees dried up for a long period. 4 repro-, sents the fruit of Peronospora infesanas on the leaves very highly magnified. The arrows represent the movements of the fungus matter; C, starch-cells, liberated by the fungoid solution and full of starch granules; D, the starch , cells of watery potatoes. They tain very little starch. ,E, the atarch. cells arranged in the potato Rnmoi are void of starch, while some are well filled; others partially so. H represents the condition of starch in water when a potato is grated down, or when the cellulose cells are rotted away by fermentation, as in the case stated. Prof. Burrill, in an address before the Illinoui Horticultural Society, upon parasitic plants, held That the -parasites now classed in the family Peronooporm, and in the two genera Peronovora and Cotopu8, are among the worst pests of the fields and gardens. Those of the former genus are especially destructive. They blight like contagion, and wither like death itself. Over forty species of the Peronosporas are known in Europe, while only six have so far been observed in this country, three of which came under the notice of Dr. Burrill. These are Peronospord infestans, on potatoes and tomatoes; P. gall& formis, on lettuce; and P. viticola; on grape* The species of the genus Cystopbs do not Beat to have the destructive effects of the former, yet must bause much loss of vitality to the ing plants. They appear as small scabs olf blotches ott leaves and green stems. Cruciferous plants, especially with us horse-radish and cabbage, are commonly thickly spotted by the parasite. The weeds known as purslane (pusly) and or (Amcvrant Its retroflex, 8) are similarly scabbed, and even the ubiquitous (Ambrosia artemisicefolia) does not escape. Returning to the characteristics of the family, we must notice the striking peculiarity, so far as fungi are concerned, of the production of Zoospores. The spores of all other fungi, upon germination, throW out one or more threads, which directly or indirectly reproduce the plant, but, though the same thing often occurs here, the more common thing is the division of the spore into five or six portions, which become free by the rupture of the spore coat. On each part two very fine hair like appendages are produced, which be come locomotive or Bans, propelling the little body for some minutes or hours through the drop of water in which they paginate, with aston ishing rapidity, as Seen under the micro scope. Having had their run, they settle down and germinate like the ordinary Spore. The term zoospore' has been , given 'on account of these motions, which were supposed, at one time, to be pe culiar to animals. Besides multiplying greatly the germin ating bodies, the zo ospores doubtless aid greatly in the dis semination of the species. Another and more proper form of fruit is produced, not however,strictly con fined to this group, the so-calledOtispore. This arises from a process of .fertiliza tion, analogous to that brOught about by pollen in flowering plants. The oospore is the winter spore, the others probably perishing during. that. season. In the spring it, too, spits up into zoospores, which appear in every way similar to those spoken of above. Much interest has lately been taken in the finding of the otispores in the potato fungus, by G Worthington Smith, of England. Its existence had not before been certainly known as such, though really it had been observed several times and named as belonging to another' a ecies. But the great loss caused by this ungo,s, and the hopes of finding some remedy, t many sharp eyes to investigating its develop eut. We wonder now that Mr. Smith's dis bovery was not made long before. The fact is 'low, however, known that this parasite, causing the rot of potatoes, is preserved during winter in the old stems or vines and in diseased tubers. Mr. Smith has followed up his discovery by making some compound of sulphur, potash, etc., which is to be tried on a large scale in England, by application to the seed tubers, the vines of course being carefully burned. In the moist climate of England this disease is much worse than with us, which is bad enough. The remedy, if indeed it proves such, will be a blessing little short of that of the potato itself. As showing fungous growths as seen under the microscope, we give a series of illustrations, showing some of the forms assumed, as shown under a high magnifying power, Fig. 1 and 2 show pear blight; Fig. 1 at 2 shows the cellular structure of the leaf; 3 shows the leaf blackened from internal disorganization ; 4 represents a sin gle structure of mycelium, having a fine silken appearance. Fig. 2 represents the general appear ance of the cellular matter, spores of the blighted bark, in their arrangement, form and of color. Fig. 3 represents a highly magnified interior view of the cells of the skin of an affected potato; traversed by a dark jointed amber. Fig. 4 exhibits the appearance of a section of a potato showing the starch-cells and vascular bundles, dotted ducts, and spiral ducts inter mixed. The largest cells shown are very highly magnified, in order to exhibit their real structure. The pentagonal lines, which will be observed inclosing the.starch granules. represent a section of three distinct cell-walls, one within the other. The interior, or third cell, contains the starch.