240 



THE DICTIONARY OF GARDENING, 



Psylla continued. 



of plants, sucking the sap through their long beaks. 

 They frequently live in company, and are often more or 

 less covered with a cottony secretion. Some species give 

 rise to distortions of such a kind as to cause them 

 to be reckoned among gall-makers. In repose, the wings 

 are sloped over the back like a penthouse, and the 

 front pair are rounded at the tip. These insects may 

 be known from Aphides by their rather larger size, rounded 

 wings, and harder bodies, and, above all, by their power 

 of leaping, which is given by the strong, thick thighs. 

 They do not show the rapid vegetative reproduction 

 or budding so general among Aphides. The species are 

 found on many different woody plants, and all have 

 very similar habits. Several occur on the Pear-tree (see 

 remarks on INSECTS under Pear), of which P. pyrisuga 



FIG. 305. PSYLLA PYRISUGA (the Line below the Insect shows 

 the natural length). 



(see Fig. 305) is probably most hurtful ; and P. Mali, at 

 times, does much harm to Apples. They secrete from 

 their bodies a sweet, clammy substance, which is pro- 

 duced at the expense of the fluids of the plants, and 

 falls on and clogs the surfaces of the leaves. This 

 weakens the food-plants considerably. During winter, 

 many of these insects are hidden in the crevices of 

 the bark, or in similar shelters; hence, no such retreat 

 should be permitted to exist in the neighbourhood of 

 valuable trees that suffer from their attacks. 



Remedies. Remove all facilities for concealment from 

 the trees and shrubs. It has been recommended to wash 

 the branches and leaves first with a solution of 2oz. soft 

 soap to a gallon of water, and to follow this up with 

 tobacco-water, Gishnrst's Compound, or 

 other insecticides, as recommended under 

 Aphides (which see). These may be 

 pumped on to the trees from a garden 

 engine. 



PTARMICA. Included under Achil- 

 lea. 



PTELEA (the ancient Greek name 

 of the Elm, used from the time of 

 Homer, here applied to a genus with 

 similar fruit). OBD. Rutacece. A genus 

 consisting of six species of hardy, un- 

 armed shrubs or small trees, natives of 

 temperate North America. Flowers 

 greenish - yellow, cymose or corymbose, 

 polygamous; calyx short, four or five- 

 parted, imbricated ; petals four or five, 

 much longed than the calyx, imbricated. 

 Leaves alternate, rarely opposite, tri- 

 foliolate or pinnately five-foliolate ; leaf- 

 lets ovate or oblong, pellucid- dotted, en- 

 tire or serrulate. The under-mentioned 

 species probably the only one in cul- 

 tivation thrives in any common garden 

 soil, and is readily increased by layers. 



P. trifoliata (three-leaved). Hop-tree ; Swamp 

 Dogwood, <fcc. tl., filaments four or five, 

 densely villous below the middle, longer than 

 the style in the sterile flowers, shorter in 

 the fertile ones. May and June. 1. long, 

 stalked; leaflets oval or oblong, mostly 

 acute, obscurely crenulated, paler beneath, 

 the lateral ones unequal-sided, h. 4ft. to 8ft. 

 1704. (G. C. n. s., xiii. 369.) 



P. t. anrea (golden). This only differs from 

 the type in the golden-yellow colour of the 

 VOUUK foliage. 



PTELIDIUM (so named from its similarity to 

 Ptelea). SYN. Seringia. OBD. Celastrinece. A mono- 

 typic genus, the species being an ornamental, stove 

 shrub. It thrives best in a compost of loam, peat, and 

 sand. Cuttings of the ripened wood will root readily, 

 if inserted in sand, under a glass, in heat. 

 P. ovatum (ovate-leaved). /. green, minute, in axillary and ter- 

 minal cymes, which are shorter than the leaves ; calyx segments 

 and petals four. June. I. opposite, coriaceous, petiolate, ovate, 

 entire, h. 3ft. Madagascar, 1818. 



PTERJS. A Fern; the term is also used in Greek 

 compounds to signify a wing, e.g., Pterocarpous, wing- 

 fruited. 



PTERIS (the old Greek name for a fern, used by 

 Dioscorides, so called from pteron, a feather; in allusion 

 to the shape of the fronds). Brake or Bracken. Includ- 

 ing Amphiblestra, Campteria, Doryopteris, Heterophlebium, 

 Litobrochia, Ornithopteris, Pcesia, Pycnodoria, &c. OBD. 

 Filices. A rather large, cosmopolitan genus (upwards of 

 seventy species) of stove, greenhouse, or hardy ferns, in- 

 cluding plants of almost every kind of venation and divi- 

 sion. Sori marginal, linear, continuous, occupying a 

 slender, filiform receptacle in the axis of the involucre ; 

 involucre the same shape as the sorns, usually mem- 

 branous, at first quite covering it, at length more or less 

 spreading. Except where otherwise indicated, the under- 

 mentioned species require stove treatment. For culture, 

 &c., see Ferns. 

 P. albo-llneata (white-lined). A form of P. cretica. 



P. aquiltna (eagle-like). Adder-spit ; Common Bracken or Brake 

 Fern ; Eagle Fern. rhiz. wide-creeping, stout, subterraneous. 

 sti. 1ft. or more long, strong, erect, straw or pale chestnut- 

 coloured, fronds 2ft. to 4ft. or more long, 1ft. to 2ft. broad, sub- 

 deltoid ; uppermost pinnse simple ; those next in order lanceolate, 

 cut nearly or quite to the rachis into triangular or linear 

 pinnules ; the lowest pinnae long-stalked, 1ft. or more long, with 

 ample, lanceolate pinnules, the latter cut down to the rachis into 

 numerous lanceolate segments, which are again fully pinnate ; 

 largest entire ultimate divisions lin. long, in. broad ; rachis and 

 both surfaces sometimes pubescent. Involucre double, or the 



FIG. 306. PTERIS ASFERICAULIS TRICOLOO. 



