November 21, 1894.] 



Garden and Forest. 



463 



permanent arrangement of large foliage-plants as a back- 

 ground for the exhibited specimens should be provided. 



A bald parallelogram of a room, with plain walls and 

 staring windows on both sides, it is difficult to render pic- 

 turesque by any collection of the rarest and most splendid 

 blossoms. From our advancing civilization and increased 

 interest in real and refined beauty of floral arrangement 

 ought to grow something better than this. It seems as if 

 somewhere in the spacious park systems of our great cities 

 some spot might be found where a building wisely planned 

 especially for such a purpose could be placed. The 

 approaches should gradually prepare the mind for the 

 impression which the interior would give. Here a softly 

 lighted vestibule in which plants with decorative foliage 

 could be skillfully disposed should lead to a recessed hall, 

 with a central fountain begirt with shade, where in vine- 

 clad alcoves easy of access the specimens could be dis- 

 played. A flower cathedral, in short, with its attendant 

 chapel, and a high altar for the display of the committee's 

 choice for the first prize, might be constructed by some 

 skillful flower-loving architect, who could give us a practi- 

 cal conception, enhanced by every appropriate decorative 

 device. Such a building, possibly, could not be the out- 

 come of one generation, but it is a good ideal to strive for. 



It is most interesting to see into what individual flowers 

 can be developed by unremitting and intelligent care, but 

 there is a higher love for flowers which yearns to see them 

 fittingly disposed, to awaken in the popular mind a con- 

 ception of the true value of floral arrangement, and to turn 

 the great artistic current of feeling in that direction as well 

 as in that of outdoor gardening. We greatly need lessons 

 in this art ; we lack examples ; we ought to be taught by 

 masters in floral design how best to show the specimens 

 on which so much loving care has been lavished, and as 

 one of the aims of horticultural societies is to develop 

 taste as well as skill, this wise endeavor should find expres- 

 sion first in an appropriate and beautiful building for 

 flower-shows. 



It is small wonder that a hall in Boston which dates 

 from the early forties is not thoroughly in keeping with 

 the artistic progress of a half-century of, improvements 

 in taste. It was creditable for the time of its erection, but 

 the city has outgrown it now, and the Horticultural Society 

 should demand more artistic headquarters, to be in keep- 

 ing with the great advance in taste everywhere. 



Hingham, Mass. M. C. RobblllS. 



The Exoascaceas of Stone Fruits. 



THE commoner forms of the fungi belonging to the Exoas- 

 *■ caceaeare quite well known throughout the United States. 

 These forms are popularly called "leaf curl" and "plum 

 pocket," the former being a wrinkled or curled condition of 

 the living leaves of the Peach, while the latter is a large hollow 

 abnormal transformation of the ovaries or young fruits of the 

 cultivated Plum. A critical study of material collected during 

 several years from various parts of the United States serves 

 to show that several species quite different from the Exoascus 

 deformans, Berk., and E. Pruni, Fuckel, exist, producinga num- 

 ber of quite characteristic deformities of the branches, leaves 

 and fruits of the genus Prunus. 



In all of the prunicolous species of Exoascus in the United 

 States the mycelium, or vegetive portion of the parasite, is 

 intercellular, that is, it grows only between the cells of the 

 host, not even sending short branches into the interior of the 

 cells. It is very irregular in its course through the tissues and 

 in the size of its cells. These are cylindrical, oblong, clavate, 

 or oval, and are joined in an irregular chain without order 

 between the cells of the host. The mycelium may be quite 

 abundant in some species and presents a very intricate 

 network of threads. In other species, or in parts of the 

 plant not so seriously affected, or in parts where the mycelium 

 is passing the winter, it is more scanty, frequently consisting 

 of isolated, oval or irregularly oblong cells. The growth of the 

 fungus in the leaves, twigs or fruit stimulates these tissues of 

 the host to an increase in the nutnber anil size of the cells, so 

 that characteristic malformations of the diseased parts appear. 

 In the leaves the increase in the number of the cells of the dis- 

 eased portion causes that part of the leaf to arch upward or 



downward in a series of irregular folds, or a somewhat cir- 

 cular spot becomes strongly arched in one direction, forming 

 a deep, wide-mouthed pocket. The twigs become enlarged in 

 diameter and variously contorted, or an early development of 

 the buds is stimulated, producing what are commonly called 

 " witches' brooms." Again, the fruit becomes transformed 

 into a large spongy mass of tissue, which is hollow and devoid 

 of the "stone" or "pit"; or only one side of the fruit is 

 affected when irregular, one-sided swellings of similar tissue 

 are developed. The floral envelopes in some species partake 

 also of the hypertrophy, and in other cases only the superficial 

 portion of the fruit is affected when the " stone" is normally 

 developed. In the latter case sometimes a warted condition 

 of the fruit appears. The young leaf-buds in some species 

 are transformed into a large spongy hollow mass of tissue 

 much resembling in texture that of the " plum pockets." 



From the interior of these deformed tissues the mycelium 

 grows to the surface and spreads, by branching out over the 

 epidermal cells just beneath the cuticle. The cells of the sub- 

 cuticular layer soon become nearly equal in diameter, and are 

 usually developed in such numbers that eventually they are 

 closely crowded, when they become angular in outline. Each 

 of the cells of the hymenium elongates perpendicularly to the 

 surface, forming cylindrical or clavate cells, which stand close 

 together upon the surface like the pile on velvet, and give the 

 appearance of a white bloom on the affected parts. These 

 cells contain the spores of the fungus. 



The following species are known in the United States: 



Exoascus deformans (Berk.), Fuckel, occurs in the leaves 

 and twigs of the Peach (Prunus Persica). The twigs are slightly 

 enlarged, but are not transformed into a spongy mass. The 

 leaves are thrown into a series of irregular folds, frequently 

 transversely to the long axis of the leaf. Sometimes the arching 

 of the leaf takes place more strongly on one side than on the 

 other, when a strong convexity appears on that side. When a 

 large portion of the leaf is thus affected it frequently bulges 

 out on one side along the middle, and the edges of the leaf are 

 drawn toward each other, the leaf appearing as if strongly in- 

 flated. In the affected portion of the leaf the green color pales 

 and the parts are more or less brightly colored with reddish 

 and yellowish tints. The leaf tissue at these parts is also thick- 

 ened and assumes a cartilaginous consistence. The paren- 

 chyma cells are frequently very much elongated and curved, 

 or sinuous in form. T he mycelium is perennial in the leaf- 

 buds, passing the late summer, autumn and winter months in 

 the tissue of the leaf-buds, and in the following spring grows 

 out with the developing leaf, multiplying more abundantly in 

 certain parts than in others. This is the reason that some 

 parts of the leaf are affected while others are free. 



Exoascus Cerasi (Fuckel), Sadeb , causes " witches' brooms " 

 on escaped trees of Prunus Avium at Germantown, Pennsyl- 

 vania. Instead of forming spurs, or Mower-buds, as in ordi- 

 nary branches, twigs are developed, giving to portions of the 

 trees a broomy appearance. The fruiting condition of the 

 fungus is frequently confined to the lower side of the leaf and 

 the leaves are not curled. This has been known as E. Wiesneri, 

 Rathay, and is sometimes confused with E. deformans. 



Exoascus insititiae, Sadeb., forms small " witches' brooms" 

 on the ends of branches of Prunus Pennsylvanica, at Temple, 

 New Hampshire. Several small twigs, frequently growing 

 from the ends of a larger one, are somewhat curved to one 

 side. The leaves are not much deformed, presenting a series 

 of small folds, and a large portion of the under surface is cov- 

 ered with the asci which give them a grayish white appear- 

 ance. 



Exoascus Pruni, Fuckel, deforms the fruit or young ovaries 

 of Prunus domestica, forming the well-known " plum pocket." 

 According to the characters which Sadebeck applies to the dis- 

 tinction of species, this Exoascus is at present only known on 

 the cultivated Plum in the United States. 



Exoascus confusus, Atkinson, occurs on the Moral envelopes 

 and ovaries of Prunus Virginiana. The Moral envelopes are 

 enlarged and distorted, becoming persistent, while the ovaries 

 are enlarged and elongated, being transformed into a spongy 

 tissue much the same as that which results from E. Pruni on 

 the cultivated Plum. 



Exoascus Farlowii, Sadeb., produces similar deformities of 

 the Moral envelopes and ovaries of Prunus serotina. 



Exoascus varius, Atkinson, produces a folding or arching of 

 the leaves of Prunus serotina, and the ends of the twigs are 

 also deformed, though a spongy tissue is not developed. In 

 external appearance this resembles the Peach-leaf curl, but in 

 the structure of the fungus it is different. In the southern 

 states frequently trees of Prunus serotina will be very badly 

 affected with both E. varius and E. Farlowii. 



