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divided into three equal branches; then each of these three branches is again divided into three branchlets, and each of these branchlets subdivided into three pedicles — upon the extremity of each is developed a beau. tiful monilliform line of highly transparent spherical spores. Figs. 16 and 17, Lign. T, are imperfect heads of the same species. This fungus, while it probably hastens decay, after once being started by the blight fungus, (S. Pyrus), does not, of itself, start the rot, unless the fruit has arrived at that period of maturity when fermentation and decay becomes a natural process, or the fruit is so unnaturally situated — as regards the conditions of moisture and temperature — that this yeast Pencillium is excited to vegetate and act as a ferment.

This species of fungus is morally, then, rather the consequence than the cause of decay in fruit.

Fig. 37, Lign. U, represents vegetating sporidia. These sporidia were placed into a watch glass, in a solution of sugar, at 10 A. M., and set aside at a temperature of 70 deg. F. At 4 P. M., six hours after, they presented the appearance seen at 37. These sporidia were taken from the apple leaf. Fig. 36, Lign. U, represents the sporidia of the plant-Fig. 35, Lign. G, vegetating. These vegetating filaments are less marked and not as rigid in appearance as the filaments of the plants, 24 and 25. Fig. 59, Lign. I, represents zoospores organizing cylindrical cells. The sporidia and fertile threads of the plants 24, 25 and 35, were placed in a solution of sugar, August 25th. August 27th, numerous zoosporoid cells were moving about actively. Fig. 59, a, b, c, d, e, and f, Lig. H, represent their different shapes. Celia were noticed on the larger ones. The zoospore a, was carefully watched. In it, near the posterior end, are two organized cylindrical cells. These cells, in a short time, were being voided, as seen at b, During the voiding, the zoospore became nearly spherical. c represents these cells void d. d represents the zoospore after voiding the cells. While it was voiding the cells, it had a slow, pulsating, revolving motion. After they were voided, it resumed its former zigzag, progressive, rotary movement.

The pear trees and pear fruit are affected in the same manner, and by the same cause as the apple and quince. Persimmon fruit is invaded, also, by the Spyaerothrca Pyrus, but it produces in them no signs of decay. The reason of this is, probably, the large amount of sugar and tannic and gallic acids thy contain, and the small percentage of water.

MUCER-NIGRICOUS-SALISB. This is a peculiar mould, of large size, which sometimes produces decay in pear-fruit. It is more apt to attack the early juicy pears, than those

which ripen later. The fertile threads on the surface of the pear occur in masses; are grizzly black by reflected light, and have a curled appearance and a crispy feel like the hair of the negro; hence its specific name. It belongs to the group Physomycetes, the order mucorini, and the genus mucor. Not finding it anywhere described, we have named it from the appearance of the aerial threads.

The pears affected with rot caused by this fungus are filled, in the decaying part, with mycelium, fig. 61, Lign. V. The mycelium is luxuriant, and the rot keeps pace with its progress, which is often so rapid that a whole pear will decay in from 48 to 72 hours. The fertile threads do not appear often on the surface till after the fruit is entirely decayed; making it appear as if it were the consequence, instead of the cause of the decay. The microscope, however, discovers the mycelium in advance of the decay.

Fig. 60, Lign. W, represents the fertile threads of the mucor nigricous, in various stages of development. a is a mature sporangium. The spores are within a thin, transparent, membranous sack, until mature, when they barst forth upon the surface. are immature sporangia. The spores show faintly through the sporangic membranes. They are inclosed in large sacs, which are themselves inclosed in the sporangic envelope. c, fig. 64, Lign. V, represents the shape of the majority of the spores, which are spherical. d represents the shape of those spores that are double and those that are oval. These are generally larger than the spherical spores. e, fig. 64, represents germinating spores. It is quite seldom that the fertile threads of this fungus appear on the surface of the fruit. When they do, they are very thrifty and rank in growth, and harsh, crisp and curled, and grizzly black, like the hair of a negro that has begun to turn gray. They often rise half an inch above the surface and appear like a curled compact mass of grizzly black hair.

The sporangia are large, bladder-shaped sacks (fig. 60, f and b, Lign 3,) terminating the fertile threads. f is the columella and m the vesicle that becomes filled with spores. They are filled with a sort of protoplasm at first, contained in sacks. This endochrome is formed into spores. These secondary sacks disappear, and the spores, when mature, make their way to the surface, as seen at a, fig. 60. The bladder-like sporangia, if not kept moist, in a few minutes after they are separated from the mycelium, or fertile threads, shrink and collapse. The spores also shrink and shrivel if not kept moist. If, after they have shrunk and shriveled, moisture be applied, they immediately assume their former plumpness In this respect they differ from most fungi and their spores. This fungus produces & rapid wet rot. The pears decayed by this mould will hardly hold together

Aug. 23, 9 A. M- Placed some mature spores of the m. nigricous in a solution of sugar, between two watch glasses, and exposed to light, at a temperature of 70° F. At three P. M., six hours after, many of the spores had vegetated and presented the appearance seen at fig. 62, a, Lign. V. Others presented no signs of vegetating. It will be seen, by referring to the figure, that three spores have been joined together by their filaments. This system of anostomosis always occurs where spores are arranged near each other in the matrix.

Aug. 24, 6 A. M -21 hours after being placed in the saccharine solution, many of the spores had vegetated so as to present the appearance seen at figs. 63 and 65, Ligns. X and V. The growth was luxuriant and rugged. This fungus only attacks the mature, mellow pear.

PROPHYLACTICS. In combatting the invasion of this fungus, we necessarily have to rely more upon "preventives” than "curatives." The preventives must be bodies which have an influence in controling mucedinous growth, and still are not injurious to the trees. Among these — that can be cheaply and readily obtained, and which, while they retard the growth of the fungus, act as manures to the trees — may be placed Sulphur, Sulphurous Acid, Sulphites, and Sulphuric Acid. These bodies are all, more or less, destructive to fungus development, and have the power of stopping fermentation. The wine-grower controls the vegetation of yeast plants (fermentation) by burning sulphur in his casks. The sugar manufacturer checks mucedinous cellular development in the juice of the cane, (preventing the formation of glucose, which would interfere with granulation) by adding a few drops of Sulphuric or Sulphurous Acid, or a small quantity of some soluble Sulphite to the freshly expressed juice.

The sporidia are mostly in the circulating juices of the tree, and in their passage become fixed, and vegetate in the tender developing leaf tissues, which afford them a matrix, with abundant nutrient supplies. The proventives should therefore be applied so as to enter the sap of the tree in its early circulation in spring, as soon as the flower and leaf-buds begin to swell or open, that they may reach the sporidia before they begin to vegetate. To this end, I would suggest the digging away of the sod or surface earth from around the trees, and the application of a compost, containing either Sulphur, Sulphurous Acid, Sulphites, or Sulphuric Acid. The refuse gas lime from the purifying vats of gas establishments, either alone or mixed with coal ashes, cinders from foundries, iron furnaces and black smith shops; or the pitch from coal oil refineries, boiled down to asphalt and pulverized, furnish cheap and appropriate materials for the purpose, containing the desired bodies for checking mucodinous growths. These should be mixed with good soil (half and half) before being applied. These bodies all contain valuable nourishment for the trees. They will also guard against many depredations from insects. Care should be taken not to use the gas lime too liberally,

RESEARCHES, Resulting in the discovery of the cause of the so called "Blister and Curl"

in the Leaves of Peach Trees, and the decay in the Peach Fruit; with some observations on the Development of the Peach Fungus (Sphaerotheca Persica).

BY J. H. SALISBURY, M. D., AND C. B. SALISBURY. For some years, in this country, the disease which produces the "Blister and Curlin the peach leaf, and decay in the peach fruit, has widely prevailed, and produced extensive ravages. It often has destroyed entire orchards of peach trees, by killing the leaves in the early part of the season. Young and vigorous trees are generally able to live through it, yet not without being materially injured. The disease attacks the young leaves as fast as they make their appearance. It produces its greatest ravages—in this climate generally-from the 10th of May to the 15th of · June. By the 15th of June the new sprouts have nearly completed their growth, and but few new leaves subsequently make their appearance. The disease, hence, has but little chance to spread further than it already has gone—it being one confined in its destructive ravages to young and tender leaves and new shoots. The leaves, by the 15th of June, having become quite firm in texture, those which are not killed or too much enfeebled and involved in the disease, begin to revive, and the trees, if not too greatly injured, begin to assume, from this date, a more and more healthy appear.

ance.

Various have been the theories respecting the cause of this disease. The one most generally received among fruit-growers is that which attributes it to spring frosts.

About the middle of May, 1862, my attention was particularly called to the careful study of the disease. On dissecting the leaves, and subjecting them to a careful microscopic examination, I found the parenchyma filled with several layers of fine myceliated threads, crossing and anastomosing with each other in various ways, forming a complete net-work among the leaf-cells (Lign. Y, Fig. 5.) On examining carefully the surface of the

leaves under the microscope, small pearl-white moniliform threads were found, making their appearance externally and proceeding from the interlacing and anastomosing filaments within the leaves.

The leaves of many different trees in different orchards were examined, and wherever a leaf was affected with the blister and curl, or either, much or little, there was found the mesh of interlacing and anastomosing filaments (fig. 5) in its parenchyma; and often, on its surface, could be discovered the moniliform fertile threads (Lign. Y, fig. 1.) In the healthy leaves there appeared no such growth. Under and near the peach trees were noticed the leaves of the Ohio Blue Grass (Poa pratense), generally white with a similar growth to that on the leaves of the peach trees (Lign. Z fig. 3), imparting to them an appearance as if a coating of fine white powder had been sprinkled over the surface, and giving the grass an unhealthy aspect.

DESCRIPTION OF FUNGUS. Group Ascomycetes.- Asci formed from the fertile cells of an hymenium. Sporidia definite, or indefinite, produced from the protoplasm of elongated or dilated cells. The fertile plants are frequently accompanied by inarticu. late or separate, simple or branched threads, which are abortive asci, known under the name of Paraphyses.

Order Perisporiacei.--Asci often evanescent. Perithecia free, astomous; at length dehiscent, often surrounded by variously shaped threads distinct from the mycelium. Asci springing from the base, tubular or saccate, often absorbed at an early stage; occasionally solitary.

Genus Sphaerotheca-Sphaerotheca Persica, Salisb.--This plant-which is a true parasitic fungus—belongs to the group or division Ascomycetes; the order Perisporiacei and the Genus Sphaerotheca. I do not find specific descriptions that are applicable in all respects to this species. The nearest approach to it is the S. Castgnei. I therefore name it after the specific name of the peach plant, to which it is so destructive.

This epiphytal plant is one of the simplest of fungi. It belongs to a group which is distinguished by the great development of the mycelium. Many of these grow on living leaves, and are very destructive-either by directly diverting the nutritive juices from their proper office and appropriating them to their own use, or by blocking up the stomates and imped. ing respiration and the free action of the rays of light and of the surrounding atmosphere, thereby involving them in disease which often results in death. The fertile threads are moniliform (figs. 1, 2, 3, Lignographs Y and Z), made up of oblong oval sporidia, arranged end to end, from which the enveloping asci are evanescent, or are early absorbed. The sporidia

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