Page:EB1911 - Volume 21.djvu/38

 and also keeps the stock from becoming hard or bark-bound. The fruit of the pear is produced on spurs, which appear on shoots more than one year old. The mode most commonly adopted of training wall pear-trees is the horizontal. For the slender twiggy sorts the fan form is to be preferred, while for strong growers the half-fan or the horizontal is more suitable. In the latter form old trees, the summer pruning of which has been neglected, are apt to acquire an undue projection from the wall and become scraggy, to avoid which a portion of the old spurs should be cut out annually.

The summer pruning of established wall or espalier-rail trees consists chiefly in the timely displacing, shortening back, or rubbing off of the superfluous shoots, so that the winter pruning, in horizontal training, is little more than adjusting the leading shoots and thinning out the spurs, which should be kept close to the wall and allowed to retain but two or at most three buds. In fan-training the subordinate branches must be regulated, the spurs thinned out, and the young laterals finally established in their places When horizontal trees have fallen into disorder, the branches may be cut back to within 9 in. of the vertical stem and branch, and trained in afresh, or they may be grafted with other sorts, if a variety of kinds is wanted.

Summer and autumn pears should be gathered before they are fully ripe, otherwise they will not in general keep more than a few days. The Jargonelle should be allowed to remain on the tree and be pulled daily as wanted, the fruit from standard trees thus succeeding the produce of the wall trees. In the case of the Crassane the crop should be gathered at three different times, the first a fortnight or more before it is ripe, the second a week or ten days after that, and the third when fully ripe. The first gathering will come into eating latest, and thus the season of the fruit may be considerably prolonged. It is evident that the same method may be followed with other sorts which continue only a short time in a mature state.

Diseases.—The pear is subject to several diseases caused by fungi. Gymnosporangium sabinae, one of the rusts (Uredineae) passes one stage o its life-histo on living pear leaves, forming large raised spots or patches whidlil are at first yellow but soon become red and are visible on both faces; on the lower face of each patch is a group of cluster-cups or aecidia containing spores which escape when ripe. This stage in the life-history was formerly regarded as a distinct fungus with the name Roestelia cancellata; it is now known, however, that the spores germinate on young juniper leaves, in which they give rise to this other stage in the plant's history known as Gymnosporangium. The gelatinous, generally reddish-brown masses of spores the teleutospores—formed on the juniper in the sprin germinate and form minute spores—sporidia—which give rise to the aecidium stage on the pear. Diseased pear leaves should be picked off and destroyed before the spores are scattered and the various species of juniper on which the alternate stage is developed should not be allowed near the pear trees.

(From a specimen in the British Museum)

Pear Scab (Fusicladium pyrinum).

1, Leaf showing diseased areas

2 Section of leaf surface showing the

spores or conidia, c, borne on long

stalks (conidiophores).

Pear scab is caused by a parasitic fungus, Fusicladium pyrinum, very closely allied and perhaps merely a form of the apple scab fungus, F. dendriticum. As in the case of the a le disease it forms large irregular blackish blotches on the fruit and leaves, the injury being often very severe especially in a cool, damp season. The fungus mycelium grows between the cuticle and the epidermis, the former being ultimately ruptured by numerous short branches bearing spore (conidia) by means of which the disease is spread. As a preventive, repeated spraying with dilute Bordeaux mixture is recommended, during the flowering season and early development of the fruit. Similar spraying is recommended for pear-leaf blister caused by Taphrina bullata, which forms swollen areas on the leaves. Pear trees may also be attacked by a great variety of insect pests. Thus the younger branches are often injured by the pearl oyster scale (Aspidiotus ostreaeformis), which may be removed by washing in winter with soft soap and hot water. A number of larvae of Lepidoptera feed on the leaves the remedy is to capture the mature insects when possible. The winter moth (Cheimatobia brumata) must be kept in check by putting greasy bands round the trunks from October till December or January, to catch the wingless females that crawl ug and deposit their eggs in the cracks and crevices in the bark. The caterpillars of the leopard moth (Zeuzera pyrina) and of the goat moth (Cossus ligniperda) sometimes bore their way into the trunks and destroy the sap channels. If badly bored, the trees are useless; but in

Pear-leaf Cluster-cups (Gymnosporangium sabinae).

1, Leaf showing groups of cups or aecidia. 2, Early stage of disease. 3, Cups

the early stages if the entrance of the caterpillars has been detected, a wire should be pushed into the hole. One of the worst pests of pear trees is the pear midge, known as Diplosis pyrivora or Cecidomyia nigra, the females of which lay their eggs in the flower buds before they open. The yellow maggots devour the seeds and thus ruin the crop. When deformed fruits are noticed they should be picked off and burned immediately. Species of aphides may be removed by tobacco infusion, soapsuds or other solutions. A gall mite (Phytoptus pyri) sometimes severely injures the leaves, on which it forms blisters—the best remedy is to cut off and burn the diseased leaves.

The Alligator or Avocado Pear is Persea gratissima, a member of the natural order Lauraceae, and a native of the West Indies and other parts of tropical America. It is a tree of 25 to go ft. high and bears large pear-shaped fruits, green or deep purple in colour, with a firm yellowish-green marrow-like pulp surrounding a large seed. The pulp is much esteemed in the West Indies and is eaten as a salad, usually with the addition of pepper, salt and vinegar. The pulp contains much oil, which is used for lighting and soap-making, and the seeds yield a deep indelible black stain which is used for marking linen. Prickly pear is the popular name for species of Opuntia (see ).

The name wooden pear is applied to the fruits of Xylomelum (nat. ord. Proteaceae), an Australian genus of trees with very thick, woody, inversely pear-shaped fruits which split into two parts when ripe.

PEARCE, CHARLES SPRAGUE (1851–), American artist, was born at Boston, Massachusetts, on the 13th of October 1851. In 1873 he became a pupil of Léon Bonnat in Paris, and after 1885 he lived in Paris and at Auvers-sur-Oise. He painted Egyptian and Algerian scenes, French peasants, and portraits, and also decorative work, notably for the Congressional Library at Washington. He received medals at the Paris Salon and elsewhere, and was decorated with the Legion of Honour, the order of Leopold, Belgium, the order of the Red Eagle, Prussia, and the order of Dannebrog, Denmark. Among his best known paintings are "The Decapitation of St John the Baptist" (1881), in the Art Institute of Chicago; "Prayer" (1884), owned by the Massachusetts Charitable Mechanic Association; "The Return of the Flock," in the Bohemiam Club, San Francisco; and "Meditation," in the New York Metropolitan Museum.

PEARL. Pearls are calcareous concretions of peculiar lustre, produced by certain molluscs, and valued as objects of personal ornament. The experience of pearl-fishers shows that those shells which are irregular in shape and stunted in growth, or