80 THE DICTIONARY OF GARDENING, 
Peristrophe—continued. 
white, lin. long. Winter. l. 3in. to 5in. long, lanceolate or 
oblong-lanceolate, long-acuminate, ‘attenuated into the paiolo, 
glabrous on both surfaces. h. 2ft. to Aft. India. (B. M. ) 
two, elliptical - oblong, both of a deep, rich carmine-purple. 
Winter. (. opposite, petiolate, ovate, somewhat acuminated, the 
lower and larger ones sub-cordate and slightly crenate. Stem 
and old branches ash-colour. h. 4ft. ndia, 1826. (B. 74; 
B. M. 2722; L. B. C. 1915, under name of Justicia speciosa.) 
PERISTYLIS. Included under Habenaria. 
PERITHECIUM (from peri, around, and thékion, 
a receptacle ; inasmuch as it surrounds the receptacle for 
the spores). The name given to certain bodies formed, 
in the processes of reproduction, in a large group of 
Fungi, the Pyrenomycetes (which see). The Peri- 
thecia vary a good deal in form, and in mode of group- 
ing together; but they are always small, and are usually 
flask-shaped. They may be almost free from the myce- 
lium, or may be imbedded in it, and, in the latter case, 
the wall is hardly distinguishable from the mass in 
which it lies. When free, the wall is often rather 
brittle, but moderately strong, and is formed of squarish 
or rounded cells, usually dark brown or black. The 
Perithecia may be scattered about singly, or crowded on 
specialised bodies. When mature, each usually contains 
several long, transparent cells of uniform width, or 
widened upwards (asci), and in each ascus there are 
generally eight spores, less often from two to six, or an 
indefinite number, for reproduction. These escape 
through a narrow neck, in which is a circular pore, or 
the aperture may be a long slit; or there may not be 
an aperture, the Perithecia bursting ultimately. Inter- 
mixed with the asci in many are numerous slender fila- 
ments, as long as the asci. They are the paraphyses, 
and their presence or absence is of consequence in dis- 
tinguishing the genera in the group. 
PERITOMA (from peritome, a cutting round about; 
referring to the base of the calyx). Syn. Atalanta (of 
_ Nuttall). ORD. Capparidee. A small genus of hardy, 
North American, annual herbs, now included, by the 
authors of the “ G Plantarum,” under Cleome. Calyx 
four-fid, cut round at the base; stamens six. Capsules 
stalked. Leaves compound, generally three to five- 
foliolate. For culture of P. aurea, see Cleome. 
P. aurea (golden ; petals essile. 
July and 9 ee to e ee — chloe: 
lanceolate, acute at both ends, entire. R. lft. The proper 
name of this plant is Cleome lutea. (B. R. xxvii. 67.) , 
PERIWINELE. See Vinca. 
PERNETTYA (named after A. J. Pernetty, 1716- 
1801, who accompanied Bougainville in his voyage, and 
was author of “A Voyage to the Falkland Islands”). 
Orp. Ericaceæ. A genus comprising about fifteen species 
(the number is inordinately multiplied by some authors) 
of hardy, or nearly hardy, rigid, very glabrous, hispid, 
or ciliated shrubs, some small; one is a native of the 
mountains of Tasmania and New Zealand, another is 
Brazilian, and the rest inhabit the mountains of Western 
America, from Tierra del Fuego to Mexico. Flowers 
white or rose-colour, small, nodding, solitary in the 
axils, or disposed in axillary or terminal racemes; calyx 
five-parted, not changing in the fruit, persistent; corolla 
urceolate or globose, shortly five-lobed, the lobes re- 
curved; pedicels curved, bracteate and bibracteolate. 
Fruit a globular berry, varying considerably in colour 
and size, generally about the size of a pea. Leaves 
usually small, alternate, short-stalked, serrated, penni- 
nerved, coriaceous, hard, persistent. The species best 
known in cultivation are those described below. For 
r ciliaris (ciliated). A. white 
Mexico, 
; Half-hardy. (G. C. n. ., X. 39.) 
P. speciosa (showy).* fl., corolla externally pubescent, with a 
very long, curved, remarkably twisted, pale purplish tube; lips 
; 3 wa Ry i 
acute, having the margins denticulated and 
setose. h. Akt. , 1849. 
Pernettya—continued. 
P. furens (maddening).* f. white, in almost sessile, solitary, 
many-flowered, axillary racemes; lobes of corolla spreading, 
rather obtuse. March. J. alternate, 14in. long, ovate-lanceolate, 
rarely sub-obovate, with serrated eT a petioles red. Chili. 
A low, moderately-branched shrub. (B. M. 4520.) $ 
P. mucronata (mucronate).* Prickly Heath. jl. white; pedicels 
axillary, bracteate, about equal in length to the leaves. May to 
July. l. ovate, cuspidate, denticulate, serrulate, stiff, shining on 
both surfaces. h. 6ft. Magellan, 1828, (B. R. 1675.) Syn. 
Arbutus mucronata (B. M. 3093; L. B. C. 1848). A considerable 
number of handsome seedling varieties have been produced from 
this species, varying in the size and colour of the berries, these 
ranging from almost black to nearly white. Perhaps the finest 
forms Tave been raised by Mr. L. J. Davis, Hillsborough, 
co. Down. 
P. m. angustifolia (narrow-leaved). A form with narrower 
leaves than the type. (B. M. 3889; B. R. 1840, 63, under name of 
P. angustifolia.) 
P. Pentlandi (Pentland’s). jl. white, zin. long, ovate-globose, 
solitary, axillary, drooping; pedicels red. June. fr. a berry, 
about the size of a large pea, dark blue-purple. l. crowded or 
sparse, zin. long and under, ovate or ovate-lanceolate, acute, 
serrulate, very coriaceous, shining. Branches and branchlets 
angled, setulose or glabrous, leafy. Andes, 1875. A rigid, 
branched, small shrub. (B. M. 6204.) 
P. pilosa (pilose).* „l. white; corolla ovate, with blunt, revolute 
teeth. May. J. ovate-elliptic, ciliately serrulated, coriaceous, 
without mucro, and callous at the point. Stem pilose, procum- 
bent. A. 6in. Mexico, 1839. SYN. Arbutus pilosa. (B. M. 3177.) 
PERNETTYA (of Scopoli). A synonym of Canarina. 
PERONIA. A synonym of Thalia (which see). 
 PERONOSPORA. A genus of minute Fungi, 
belonging to the White Moulds,’ one of the groups 
included among the mildews. There are many species 
in the genus, and all of them are parasitic on plants, 
i.e., they grow in and upon living plants. They prefer 
the leaves and young stems—at least they are most 
conspicuous upon these—but they run through all parts, 
from roots to seeds, though showing themselves usually 
only on the younger green organs. They are confined 
to herbs as their hosts, except in one or two cases, e.g., 
P. sparsa, on leaves of Roses. Some of them grow on 
cultivated herbs in gardens, and are frequently most 
injurious to these plants. Several of the more destruc- 
tive species are briefly described below; but a short 
account of the general structure and modes of repro- 
duction characteristic of the genus must first be given. 
We select as a type Peronospora nivea, which is 
very common upon the leaves, stems, and roots of wild 
Umbellifere, and also upon the garden Carrot, Parsley, 
and Parsnip. A portion of a leaf attacked by this. 
Fungus may be recognised by its yellowish-green colour 
above, passing into brown. The lower surface of the 
patch bears a white coating, which, under the micro- 
scope, is seen to consist of erect, branched stalks of 
very small size. These stalks emerge through the 
stomata of the leaf. Each is forked once or twice, and 
bears, towards the tip, from one to four horizontal 
branches, each forked once, twice, or thrice, and ending 
in straight, short branchlets. Each of the latter bears 
on its tip a small cell, called a conidium (see Fig. 
91, a, b). On tracing the erect stalks downwards into 
the leaf, they are found to arise as branches from an 
| abundant mass of filaments (mycelium) of a Fungus. 
This mycelium is spread through all parts of the plant, 
lying in the intercellular spaces, or boring through the 
cell-walls, and drawing nourishment from the contents 
of the cells by means of numerous minute suckers 
(haustoria). The host-plants are soon destroyed by the 
Fungus, and the diseased parts either dry up, or, if 
| fleshy, e.g., roots and tubers, they become soft, rotten, 
and pulpy. Reproduction is effected by means of the 
conidia and of oospores. The conidia do not at once 
reproduce the Fungus, but, when placed in water, their 
contents divide (see Fig. 91, b), into five or six small, 
egg-shaped masses, or zoospores, each furnished with 
two hairs (cilia), which they can move, and thus they 
can swim in water, e.g.,in a dewdrop or raindrop. After 
