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Potato-disease Fungus

This is denied by Prof. De Bary, of Strasbourg, and by others. Mr. A. S. Wilson has brought forward a theory, with reasons in support of it, connecting with the Potato-disease Fungus numerous small, oval bodies (that are white by reflected, and dark by transmitted, light), which are very abundantly scattered through the tissues of Potato-leaves, &c. He and Mr. Smith believe that they have traced these small bodies into actual connection with the undoubted mycelium of P. infestans. The bodies, on analysis, are found to consist largely of particles of oxalate of lime, with a basis of protoplasm. Mr. Wilson regards them as a resting condition, analogous to the sclerotia of other Fungi, e.g., that of Peziza postuma, in its uses to the Phytophthora. The true nature of the bodies has been hotly discussed in the "Gardeners' Chronicle" during the years 1883-85. Mr. Wilson regards Potatoes as almost all infected throughout their tissues by these resting masses of the Fungus, which, he considers, emit mycelium, and give rise to disease, under conditions favourable to the growth of the Fungus. Much has been written on remedies for the Potato disease; yet it can hardly be said that any methods have been discovered really efficient in securing the Potato crop against this scourge. Beyond doubt, the unnatural conditions induced by continuous cultivation and propagation from the tubers, have rendered the plants a more easy prey to the Fungus, and more liable to suffer severely from its attacks, than uncultivated plants would be; and this is seen if the effects on the Potato are contrasted with those on the Bitter-sweet, a plant also occasionally attacked by the Fungus. Prevention is best promoted by selecting, as seed tubers, varieties known to resist disease, since some are much hardier than others in this respect. The soil should be well drained, and there should be free circulation of air around the plants, to promote evaporation, since moisture, confined air, and warmth, promote the rapid growth of the Fungus. The seed tubers should be planted uncut, or the cut surfaces should be allowed to heal, or may be seared with a hot iron, or otherwise coated over, before being put into the soil. All tubers that show traces of disease, and all dead stalks, leaves, &c., should be burned, to prevent the propagation of the disease through them. Of recent years, Mr. Jensen, of Copenhagen, has strongly advocated "protective moulding," and his views have been stated and supported at some length by Mr. C. B. Plowright, in the "Gardeners' Chronicle." The system was also suggested by Dr. Lang, in 1858; but it has not been generally adopted. Mr. Jensen's method may be briefly summarised as follows: The ground should be thoroughly worked and quite friable, and the potatoes should be planted in rows about 30in. apart. The first moulding should be about 4in. high, and flat on top. The protective moulding should be done as soon as diseased spots appear on the plants, and, in any case, should not be deferred later than the time of Wheat-harvest: it is effected, on a small scale, in gardens, by the use of a hoe; on a large scale, in fields, by a specially-formed plough. The layer of earth should be, when it has settled down, not less than 4in. thick along each side of the row, above the tubers. At the same time, the tops should be bent over to one side of the row, and allowed to wither; and they may then be cut off and removed. The tubers may be lifted in about a week after the removal of the tops. This system proceeds on the belief that the tubers are infected by conidia and zoospores washed by showers from the leaves and through the soil on to the tubers, and not by mycelium through the stalk. Mr. Jensen also recommends disinfecting the seed tubers by storing them for four or five hours in a dry-air chamber, at a temperature of from 100 deg. to 105 deg. Fahr. Of course, other host-plants of the Fungus, whether wild or cultivated, ought not to be grown in the neighbourhood of Potatoes. Attempts have been made to substitute some other species of tuber-forming Solanum for S. tuberosum, but without great success. The most promising seem to be S. Commersoni and S. Maglia, the former of which appears to be uninjured by P. infestans.

PIARANTHUS (from piaros, fat, and anthos, a flower; alluding to the shape of the blossoms). ORD. Asclepiadeae. A genus comprising, perhaps, half-a-dozen species of greenhouse succulents, with low, deeply four-jointed stems, natives of South Africa. Flowers mediocre, often fasciculate; calyx small, five-parted; corolla campanulate, deeply five-cut, the lobes narrow, acuminate, valvate; corona lobes five, inflexed. The species have the general habit of Stapelia (which see for culture).

P. pullus (dark-flowered). fl. three or four together; corolla dark purple, the segments lanceolate, silky above, replicate. August. Branches usually hexagonal, erect; angles a little sinuated, having strong, spreading teeth. h. 6in. 1774. (B. M. 1648.) P. geminatus (twin). The correct name of plant described in this work as Podanthes geminata.

PICEA (from pix, pitch; the trees produce abundance of resin). Silver Fir. SYN. Abies (of Don). Including Veitchia. ORD. Coniferae. A genus comprising about a dozen species of mostly hardy, evergreen trees, inhabiting the extra-tropical regions of the Northern hemisphere. Flowers monaecious. Leaves acicular, spirally scattered, with the midrib prominently quadrigonal or sub-terete, contracted into a very short, articulated, persistent petiole. Cones ovoid or oblong-cylindrical, erect or horizontally spreading; the bracts not falling away from the axis at maturity, as in Abies. Owing to a succession of blunders in works treating on Conifers, the generic names Abies and Picea are generally transposed. For culture, see Abies.

P. ajanensis (Ajona). shoots glabrous when young, yellowish-brown, marked with oblong, smooth, prominent cushions. l., those on the side shoots in many rows, but twisted at the base so as to be all in the same horizontal plane; on the upper surface of the branch appressed, parallel in direction to the branch; all flattish, linear-oblong, rather obtuse, not spinetipped; upper surface three-ribbed; underneath, one-ribbed. cones erect, 1in. to 2in. long, 3/4in. broad, oblong, tapering to each end; scales shining-brown, oblong-ovate. h. 70ft. to 80ft. Japan, 1861. A beautiful Fir, resembling P. excelsa, but more elegant. SYN. Abies Alcoquiana, of gardens. (B. M. 6743; G. C. n. s., xviii. 183.) P. alba (white).* White Spruce. young shoots very glaucous. l. less numerous, longer, and more pointed than in other species, somewhat glaucous, scattered around the branches, erect, quadrangular. cones oblong-cylindrical, light brown, small when ripe; scales loose and thin, round or bluntly pointed, with entire edges. h. 30ft. to 40ft. Canada, &c., 1700. (F. d. S. 2251.) P. Alcoquiana (Alcock's).* young shoots covered with long, weak hairs. l., those on the leader shoots appressed; on the lateral, given off on all sides; all rigid, more or less curved, linear-oblong, four-sided, flattened at the top. cones deflexed, 2in. to 3in. in length, oblong, tapering to both ends; scales shining oblong-ovate. h. 90ft. to 120ft. Japan, 1861. A fine pyramidal tree. (G. C. n. s., xiii. 212.) P. communis (common). A synonym of P. excelsa.

P. Engelmanni (Engelmann's).* l., in young plants, numerous, stout, rigid, acute, slightly recurved, deep green, more distinctly quadrangular than those of any other American species. cones 2in. to 2 1/2in. long. h. 80ft. to 100ft. Rocky Mountains, 1864. A stately tree.

P. E. glauca (glaucous). A beautiful glaucous, silvery variety, very handsome and attractive.

P. excelsa (tall).* Burgundy Pitch-tree; Norway Spruce Fir. l. scattered, quadrangular. cones cylindrical, terminal, pendent, 5in. to 7in. long, 1 1/2in. to 2in. broad; scales naked, truncate at the summit, flat, 1in. to 1 1/2in. long, and about 1/2in. broad. North of Europe, particularly Norway, 1548. A well-known, lofty tree. SYN. P. communis. The varieties are very numerous, the most important being the following:

P. e. attenuata (thin-leaved). A slender-growing form, with small and thinly-set leaves, which lie close to the branches. SYN. P. e. tenuifoll P. e. aurea (golden). A striking form, with long, curved, glaucous green leaves, which are tipped with gold.

P. e. Clanbrasiliana (Lord Clanbrasil's).* A very dwarf, dense, slow-growing shrub, rarely exceeding 4ft. high. A more erectgrowing form of this variety is known as stricta.

P. e. elegans (elegant). l. more erect than in the type. h. 5ft. to 6ft. A compact, dwarf, and slow-growing bush, with short branches. P. e. eremita (solitary). Very like P. e. monstrosa, but having shorter and thicker branches. Bark reddish. SYN. P. miniata.

P. e. Finedonensis (Finedon). l., young ones on the upper side of the shoots, and the wood also, at first of a pale yellow, changing to a bronzy-brown, and, when fully matured, to a light green; those on the under side, and where shaded, more or less green from the first.

P. e. Gregoryi (Gregory's). A densely-branched, conical, slow-growing bush, of a bright green hue.

P. e. horizontalis (horizontal). A variety with a horizontal habit, and more curious than beautiful.

P. e. inverta (pendulous-branched). A very elegant weeping form, of free growth. h. 50ft. to 80ft.

P. e. monstrosa (monstrous). A curious variety, with elongated, straggling branches, very sparsely furnished with lateral growths. P. e. nana (dwarf). A synonym of P. e. pygmaea.

P. e. pumila glauca (low-growing, glaucous). l. nearly erect on the branches. A very dwarf, spreading, slow-growing variety; very distinct and pretty. P. e. pygmaea (pigmy). A diminutive variety, of a pyramidal shape. h. 1ft. SYN. P. e. nana.

P. e. pyramidalis (pyramidal). A dwarf, conical, slow-growing variety, suitable for rockwork.

P. e. tenuifolia (narrow-leaved). A synonym of P. e. attenuata. P. e. variegata (variegated). A form with yellow, but somewhat inconstant, variegation.

P. Glehnii (Glehn's). l. crowded, in many rows, curved, linear, four-sided, sharply pointed. cones linear-oblong, 1in. to 2in. long, 1/2in. to nearly 1in. wide; scales leathery, slightly straited, wedgeshaped, upper free portion rounded, denticulate, longer than the broadly lanceolate, denticulate bracts. Japan, 1880. A dwarf, dense-growing tree. (J. L. S. xviii. 513.) P. jezoensis (Yesso). l. linear, close set, and arranged spirally around the stem, sharp-pointed, with a prominent midrib on both sides. cones cylindrical, 2in. to 2 1/2in. long, 1in. in diameter, obtuse both at base and apex, pendulous, terminal; scales undulated, irregularly toothed at the free edge. h. 100ft. to 120ft. Japan, 1879. A tall, fast-growing tree. (G. C. 1850, 311.) P. Maximowiczii (Maximowicz's). l. rigid, acute, erect, 1/2in. long, dark green. A species that does not thrive in this climate, presenting, according to Messrs. Veitch, very miserable-looking specimens, and, therefore, not recommended. (G. C. n. s., xiii. 363.) P. Menziesii (Menzies').* l. linear, mucronate, incurved, turned in every direction, resupinate from being twisted at the base, silvery beneath, 2in. long, rigid, acute. cones pendulous, cylindrical, generally 3in. long, and about 1in. broad; scales with a dry, shrivelled appearance, gnawed on the margin, about 3/4in. long, 3/8in. broad. h. 50ft. to 70ft. North California, 1831. A tall tree, with regularly whorled, somewhat stiff branches. P. miniata (red-branched). A synonym of P. excelsa eremita. P. Morinda (Morinda). A synonym of P. Smithiana.

P. nigra (black). Black Spruce. l. solitary, regularly disposed all round the branches, erect, 1/2in. long, somewhat quadrangular. cones cylindrical, 1 1/2in. to nearly 2in. long, and nearly 1in. broad, blackish-purple; scales rounded, somewhat undulated, with crenulated or divided apices. h. 50ft. to 80ft. North America, 1700. The branches of the Black Spruce are drooping, and the tree is more useful for economic than ornamental purposes. P. obovata (reversed-egg-coned). This species is said to resemble P. excelsa, but, owing to its very early growth, is unsuitable for cultivating in England. Siberia.

P. Omorika (Omorika). l. flattish, straight or curved, linear-oblong, obtuse, 1/2in. to 3/4in. long, shining green beneath; the upper side with a prominent midrib. cones Larch-like, 1 3/4in. long, 3/4in. thick. Buds ovoid, clothed with ovate-lanceolate scales. Servia, 1884. A tall and distinct Fir. (G. C. n. s., xxi. 308-9.) P. orientalis (Eastern).* l. solitary, acute, sub-quadrangular. cones sub-cylindrical, pointed at the apex, 3in. long; scales broader than long, slightly angular-ovate, rounded at the apex, sub-entire. Taurus and Caucasus, 1825. A somewhat dense-growing, lofty tree P. Schrenkiana (Schrenk's). A tall tree, considered to be a variety of P. obovata, found on the Altai Mountains, but not become acclimatised in Britain. P. Smithiana (Smith's).* l. compressed, tetragonal, straight, awl-shaped, acutely pointed, 1in. to 1 1/2in. long, scattered in insertion. cones ovate-oblong, 6in. long, 2 1/2in. broad; scales obovate, roundish, coriaceous, rigid, smooth on the margin. h. 80ft. to 120ft. Himalayan Mountains, 1818. A well-known, very noble, and beautiful Spruce Fir, succeeding best when planted at great elevations, or on cold, late soils. SYN. P. Morinda. P. Tsuga (Tsuga). See Tsuga Sieboldii.

PICOTEE. Picotees are only distinguished from Carnations by the markings of their flowers. The petals of a Carnation flower, other than a self, are either flaked or barred; while those of the Picotee have a ground colour, and are edged with a second colour, which is used to separate the varieties into the divisions referred to below, according as the edging is lightly or heavily shown. The plants are propagated in the same way, and succeed under the same treatment, as Carnations; their flowers are superior, and the colours more clearly defined, when properly grown under glass, but, for ordinary purposes, the plants succeed admirably in the open air. Subjoined is a selection of Picotees from the several divisions. For details of culture, see Carnation. Heavy Purple-edged. ADMIRATION (Turner), JESSIE (Turner), LIZZIE TOMES (Dodwell), MRS. A. CHANCELLOR (Turner), MRS. SUMMERS (Simonite), MURIEL (Hewitt), NOVELTY (Matthews), PICCO (Jackson), REDBRAES, RIVAL PURPLE (Hooper), TINNIE (Dodwell), ZERLINA (Lord).

Heavy Red-edged. DR. EPPS, ENSIGN (Fellowes), J. B. BRYANT (Ingram), JOHN SMITH (Bower), LORD VALENTIA (Kirtland), LOTHAIR (Fellowes), MISS SMALL (Fellowes), MRS. BROWN (Payne), MRS. DODWELL (Turner), PICTURATA (Fellowes),