C. NIGRA (syn C. Celsiana).—­A tree 20 feet high, with stout branches, and downy, spineless shoots.  Leaves large, ovate-acute, deeply incised, glossy green above and downy beneath.  Flowers large and fragrant, pure white, and produced in close heads in June.  Fruit large, oval, downy, and yellow when fully ripe.  A native of Sicily, and known under the names of C. incisa and C. Leeana.  This species must not be confused with a variety of our common Thorn bearing a similar name.

C. OXYACANTHA.—­Common Hawthorn.  This is, perhaps, the most ornamental species in cultivation, and certainly the commonest.  The common wild species needs no description, the fragrant flowers varying in colour from pure white to pink, being produced in the richest profusion.  Under cultivation, however, it has produced some very distinct and desirable forms, far superior to the parent, including amongst others those with double-white, pink, and scarlet flowers.

C. OXYACANTHA PUNICEA flore-pleno (Paul’s double-scarlet Thorn), is one of, if not the handsomest variety, with large double flowers that are of the richest crimson.  Other good flowering kinds include C. Oxyacantha praecox (Glastonbury Thorn); C. Oxyacantha Oliveriana; C. Oxyacantha punicea, with deep scarlet flowers; C. Oxyacantha rosea, rose-coloured and abundantly-produced flowers; C. Oxyacantha foliis aureis, with yellow fruit; C. Oxyacantha laciniata, cut leaves; C. Oxyacantha multiplex, double-white flowers; C. Oxyacantha foliis argenteis, having silvery-variegated leaves:  C. Oxyacantha pendula, of semi-weeping habit; C. Oxyacantha stricta, with an upright and stiff habit of growth; C. Oxyacantha Leeana, a good form; and C. Oxyacantha leucocarpa.

C. PARVIFOLIA.—­North America, 1704.  This is a miniature Thorn, of slow growth, with leaves about an inch long, and solitary pure-white flowers of large size.  The flowers open late in the season, and are succeeded by yellowish-green fruit.

C. PYRACANTHA.—­Fiery Thorn.  South Europe, 1629.  This is a very distinct species, with lanceolate serrated leaves, and pinkish or nearly white flowers.  The berries of this species are, however, the principal attraction, being orange-scarlet, and produced in dense clusters.  C. Pyracantha crenulata and C. Pyracantha Lelandi are worthy varieties of the above, the latter especially being one of the most ornamental-berried shrubs in cultivation.

C. TANACETIFOLIA.—­Tansy-leaved Thorn.  Greece, 1789.  This is a very late-flowering species, and remarkable for its Tansy-like foliage.  It is of unusually free growth, and in almost any class of soil, and is undoubtedly, in so far at least as neatly divided leaves and wealth of fruit are concerned, one of the most distinct and desirable species of Thorn.

Other good species and varieties that may just be mentioned as being worthy of cultivation are C. apiifolia, C. Crus-galli horrida, C. orientalis, and C. tomentosum (syn C. punctata).  To a lesser or greater extent, the various species and varieties of Thorn are of great value for the wealth and beauty of flowers they produce, but the above are, perhaps, the most desirable in that particular respect.  They are all of free growth, and, except in waterlogged soils, thrive well and flower freely.