are succulent, soft, and abundantly supplied with nutritive materials. It is thus seen to have two different and well marked modes of fruiting, and several different forms of sporidia. (Figs. 24, 40, 41, 43 and 48 to 58, Lignographs P. Q, N, I, O, R.)

This plant is strictly a parisitic fungus, that affects organic tissues; and appears to be poisonous both to plants and animals. Its sporidia are often inhaled in large quantities during its period of rapid reproductive development; and frequently the expectorated sporidia are found vegetating. That the inhaled sporidia produce more or less irritation of the pulmonary mucous membrane is quite probable, from the fact that in walking over rich boggy grounds, where the surface is more or less broken, exposing the fresh peaty soil, especially during the months of June, July, August and September; or in passing, in the morning or evening, over positions where hang the vapors from boggy localities, the fauces, throat, and pulmonary membrane becomes dry, feverish and congested, which lasts often for hours after removal from continued contact with the exciting cause; and from the further fact that the expectorated mucus, after leaving such localities, is found filled with the sporidia of this fungus.

This fungus belongs to the group Ascomycetes, to the order Prisporiacei, and the genus Sphærotheca; for a description of which, see the paper on the Cause of the Blister and Curl in Peach Leaves, &c. This species resembles, and may be found to belong to the peach fungus (S. Persica); but as there appears, at this stage of the investigation, to be specific differences, and not finding it within our range of reading described, we name it after the generic name of the family of plants it so much affects—the S. Pyrus.

This fungus resembles, somewhat, species arranged under the genera Sporochisma and Bloxamia, which belong to the group Coniomycetes, and the order Phragmotrichium. There are, however, many marked peculiarities about this plant that separate it from those of the Coniomycetous, and unite it with those of the Ascomycetous group.

One species of Sporochisma, the S. Spilocaea, affects apples, forming the black specks on their surface, which are occasionally so numerous as to make them unsalable. In producing blight, the sporidia begin to develop in the soft, viscid layer of cambium, and follows the vessels up and down from the point of starting. As fast as the mycelium progresses, death ensues. Figs. 14 and 20, Lignographs E and F, and figs. 24, 25, 29, 34, 35, 42, 43, 45, 46 and 47, Lignographs P, G, K, L, Q, M, O and N, represent the usual forms presented by this fungus at different stages. The fertile threads and lines and masses of spores seen at figs. 24, 25, 40, 43, &c., Lignographs, P, G, &c., appear on the dead leaves and twigs, like a

fine dark brown or black carbonized dust. So imperceptible is it that it is with difficulty discovered to be a plant at all. Wherever the mycelium and fertile threads appear, the tissues die, and become carbonized and black; especially is this the case with leaves. Figs. 29 and 30, Lignograph K, represent an early stage in the development of the fertile threads from the discs or perithecia.

The various forms and groupings of sporidia are represented at figs. 20 and 21, Lignograph F, and figs. 24, 25, 26, 27, 28, 31, 32, 40, 41, 42, 43, and from 48 to 58, Lignographs P, G, K, Q, J, N. O and R.

Fig. 32 represents a paraphysis bearing upon its summit spores.

Fig. 24 b, represent young asci.

Figs. 38 and 39 represent portions of the fertile filaments of the plant, seen at fig. 24.

Fig. 11, Lignograph E, represents the mycelium of the fungus, as it appears in the cambium of the limbs which it attacks. Decay follows close on the advance of the mycelium, which runs along in lines in the direction of the new woody fibers.

Figs. 8, 9, 10, 12, 13, 14, Lignographs S and E, and fig/42 t, Lignograph Q, represent most of the forms of fertile threads on the branches. Occasionally fertile moniliform lines of spores, like those seen at figs. 8 and 14, Lignographs S and E, may be seen on them and the tender leaves in June and July, during the rapid deposit of woody matter and the abundant supply of nutritive juices.

Fig. 8, Lignograph S, and figs. 40 and 41, and k, 7 and e, fig. 42, Lignograph E, represent masses and lines of sporidia, which are developed either on or in the course of the fertile threads. The mass, fig. 41, is vegetating.

Fig. 42 represents the mycelium and fertile threads of the S. Pyrus, from a branch of a quince tree; and figg. 40, 41, 43, and t, fig. 42, the fertile threads running into lines and masses of sporidia. Figs. 45, 46 and 47, Lignographs M, N and O, represent the appearance of the discs or Perithecia, under the cuticle, from which emanate the fertile threads, and the various forms of sporidia, figs. 48, 49, 50, 51, 52, 55 and 58, Lignographs J, N and R. The other forms and arrangements of spores are seen at figs. 53, 54, 56 and 57. The spores, 40, 41 and 43, and d, e, g, h, i, k and 1, fig. 42, are produced on the fertile threads, above the surface, and which are believed to be connected directly with the mycelium, without the intermediate Perithaceia, figs. 45, 46 and 47. In the Perithaceia, the forma tion of fertile threads and asci and sporidia, commences at the center and most depressed portion, as seen at fig. 46, and gradually fill up and occupy the whole concavity with fertile threads. In the perithecium (fig. 47) no fertile threads are yet seen protruding above the lid. Fig. 42 f, are elongated, oval sporidia; m, m, m, fig. 42, are a class of yellowish, quite

refractive bodies, that contain smaller cells of the same nature. Fig. 42 s, are highly refractive, transparent, spherical spores, form a beautiful species of pencillium, that is, the yeast plant of the decaying quince fruit. Fig. 42, t, fertile threads attached to the mycelium.

The mycelium, during the early stages of decay, is transparent; in more advanced stages it becomes a dirty, greenish brown, and in still more advanced conditions a brownish black, at which stage the decayed flesh of the fruit becomes either dark brown or black. Very often there can be no connection traced between the masses and lines of spores, figs. 40, 41, 43, and d, e, g, k, i and l, fig. 42, and the fertile threads or mycelium. They are often found attached to the hairs of the fruit branches.

The sporidia begin to vegetate in the cambium (new wood and bark) of the more recent, tender, and smaller limbs early in June. This takes place often some distance from the extremity, but more often at or near the extremity. At first a dead patch on the side of the limb, of an oblong shape, or a dead rim round the limb is noticed. On making a section through the limb, early in the disease, the newly formed layers of wood and bark only are found dead; while the heart wood remains alive, frequently for several weeks, through which the nutrient juices pass to, and preserve vitality in the extremity of the branch. At this stage there are seldom found any fertile or sterile threads upon the surface. If, however, the outside bark be removed, dead lines will be seen running along in the direction of the fibers, in the cambium; and in these dead lines and patches, and even in advance of them, will be found the minute filaments of the mycelium seen at fig. 11, winding about among the cells.

This fungus attacks the quince, pear and apple fruit at all stages of its growth. In the former, the first attack is when it is about the size of a hazel-nut. Much of the fruit decays when it is from one-third to one-half grown, and still more as the fruit is maturing. When the fungus once begins to develop in the mature fruit, it grows luxuriantly, and decay follows close the advance of the mycelium. In the early stages of development, and also when excluded from the air, the sporidia and fertile threads are white and transparent. As they advance toward maturity, they become darker and darker; till finally, in mass, by reflected light, they appear a dark brownish black. Singly, and by transmitted light, they appear a dark yellowish brown. The fertile threads grow by pullulation. The spores 40, 41, 43 and k, l and d, fig. 42, are produced on the fertile threads that rise above the surface, whilst the spores, 48, 49, 50, 51, 52, 55, and 58, are produced from fertile threads arising from discs or perithaecia.

Fig. 20, Lignograph F., represents one form of the fertile threads of the fungus that attacks the apple-fruit. It resembles that which attacks

peach leaves and the peach fruit. Wherever it attacks the apple, it produces decay as fast as the mycelium advances. It is not usual for the fertile threads to appear. Generally, the plants in the apple-fruit consist only of mycelia; especially while the apple hangs on the tree. The applefruit, like the peach, is attacked and injured most by this fungus, just previous, and at the period of ripening. In 1862, it destroyed in Ohio a large portion of the apple crop, many of them decaying and falling before they were fully matured. Fig. 23, Lign. B, represents a body which often occurs in the flesh of the fruit.

Fig. 22, Lignograph B, represents the mycelium, when it occurs in the fruit. It is very rugged and luxuriant in appearance, and extends through all parts of the fruit affected. The decay advances as rapidly as progresses this mycelium. Where the trees are affected with blight, the fruit on such trees is sure to be affected, more or less, with this fungus; either when green, or just before and at its maturity. The apple-fruit is liable to be attacked with this fungus at all stages of its development. Often from a half to three-quarters of the crop, and sometimes a greater propor tion, is destroyed during the month of June and the early part of July. When the fruit survives this period, it seldom decays much till it is approaching maturity, when it again is attacked and often decays rapidly and prematurely, in large quantities. The next period of attack is after it is picked and laid away for fall and winter use. At this period, the fungus is particularly luxuriant and destructive. The appearance of the mycelium in the fruit is seen in fig. 22, Lign. B. It is peculiarly rugged and rapid in growth, decay keeping pace with its advance.

Figs. 20, 12, 14, Lign. E and F, and figs. 40, 41 and 43, Lign. Q, represent the appearance of the fertile moniliform, threads and chains of sporidia, containing in their course masses of spores. The moniliform threads, figs. 14 and 20, are the most abundant during the early and rapid decay of the fruit. In more advanced stages of decay, the rigid fertile threads and masses of spores are developed. Sometimes the fertile moniliform chains of spores are simple, and at others, compound. The simple and compound threads arise from the same source.

A beautiful species of Pencillium is developed abundantly in decaying apples (and other fruit). This fungus is the yeast plant of decaying apples. It produces the numerous small spherical and highly transparent spores that are scattered over the field; in examining the apple fungus, fig. 14, &c, this species of Pencillium is white and transparent, producing beautiful, clear, highly refractive spherical spores, fig. 15, Lign. E. The productive heads are terminal, and often are beautifully triply trichotamous, (fig. 18, Lign. T); that is, the fertile thread is first symmetrically

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 beautiful 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. H, 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 ƒ, 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 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 Spyderotheca 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 they 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