Derivation. Pteron, a wing; karua, the common walnut. The fruit has wings; and, except in these, resembles that of the walnut.

1. P. CAUCA'SICA Kunth. The Caucasian Pterocarya.

Identification. Kunth in Annal. des Scien. Nat., 2. p. 346.

Synonymes. Juglans pterocarpa Michx. Fl. Bor. Amer., 2. p. 192., Bieb. Fl. Taur. Supp. 33. p. 622., Willd. Sp. Pl., 4. 455., Spreng. Syst., 3. p. 865.; Rhús obscurum Bieb. Fl. Taur. Cauc., no. 606.; J. fraxinif dlia Lamond MS., N. Du Ham., 4 p. 182.; Fraxinus lævigata Hort Par. Engravings. Our fig. 1276. from a seedling plant, and the plate of this tree in our last Volume Spec. Char., &c. Leaflets, in a leaf, about 19; ovate-oblong, acuminate, argutely serrate, glabrous; each with the lower or hinder side of its base attached to the petiole. (Lamarck MS., and Spreng. Syst. leg., iii. p. 865.) The following description is translated from that written by Poiret, published in the Encyclopédie Méthodique:-"A tree, about 40 ft. high, with an ample and tufted head. Young branches brownish green, very smooth, glossy. Pith disposed in thin membranes, placed transversely, and at about a line distant from one another: J. règia has its pith arranged in a similar manner. Leaves alternate, very large, commonly having 19 leaflets each, which are oblong, denticulate with blunt teeth; have their upper surface very smooth, almost glossy, and of a beautiful rather dark green, their under surface paler; and are disposed almost alternately. Buds, when bursting, of

1276

a rusty or brownish red colour. One remarkable character, and which serves to distinguish the species clearly, is, that each of the leaflets has one side of its base shorter than the other, and one of them attached, at least while the leaf is young, to the petiole. It occurs, in many instances, that, when the leaf gets old, the attached part of the leaflet becomes distinct from the petiole; but it is always the case that one side of the base is longer than the other. The petiole is round and very tumid at the base, smooth, and of a beautiful clear green." This tree is a native of moist woods at the foot of Caucasus, where it was discovered by Steven, and described by him in the Mém. Soc. Nat. Cur. Mos., iii. p. 247, and iv. p. 70.; as noticed by Bieberstein in the Supplement to his Flora Taur. Cauc, quoted above. It was introduced into England as J. fraxinifòlia, several years since, and there are specimens under that name in the Horticultural Society's Garden, and in the collection of Messrs. Loddiges, where they form broad bushy plants, not yet more than 8 ft. or 10 ft. high. At Croome, in Worcestershire, there is a tree, 15 years planted, which is 25 ft. high. This species appears to have been first brought into notice by the elder Michaux, who, on his return from Persia in 1782 (see p. 1411.), introduced into France a plant from the shores of the Caspian Sea; which, according to Bosc, was the first that had ever been seen in Europe, and which still exists at Versailles, flowering there every year. It is described as growing from 20 ft. to 30 ft. high; and, though affected by frost, is yet sufficiently hardy to be classed among ornamental trees of the third rank. It is readily propagated by layers. For small gardens, and diminutive arboretums, this tree may serve very well to exemplify the Juglandaceæ. Care should be taken to train it to a single stem, and not to plant it in soil so rich and moist as to prevent it from ripening its wood. Perhaps, also, something might be gained in point of hardiness by grafting it upon the common walnut, either on the collar of the stock, in order to form dwarf trees, or bushes; or standard high, in order to form trees that would from the first have clear straight stems, and as they would ripen their wood better, in consequence of growing slower than low trees or bushes, so they would perhaps show blossoms and ripen fruit. Some years ago, Messrs. Booth of the Floetbeck Nurseries reintroduced this species into Britain as a new tree (see Gard. Mag., vol. xi. p. 207.), under the name of Pterocàrya caucásica, being not aware of its identity with Juglans fraxinifòlia. Plants, in London, are 2s. 6d. each; and at Bollwyller, 3 francs.

CHAP. CIII.

OF THE HARDY LIGNEOUS PLANTS OF THE ORDER SALICA CEÆ.

ALL the plants of this order are ligneous, and included in the genera Salix L. and Pópulus L., which agree in having the flowers unisexual, and those of the two sexes situated upon distinct plants, disposed in catkins, and individually subtended in the catkins by a bractea, termed a scale by many botanical authors; in the seeds being contained in a capsule of one cell and two valves, and each seed bearing a tuft of longish white hairs; and in the leaves having stipules. The points of structure in which the genera differ will be found in the following characters; the essential distinction being in the number of stamens:

SALIX L. Bractea to the flower of each sex entire. Male flower consisting of 1-5 stamens, more in a few species, and of one or more glands inserted contiguously to the stamens. Female flower consisting of a pistil that is stalked or sessile, or nearly sessile; and one or more glands inserted contiguously to it. Leaves, in most, with the disk more or less lanceolate. (Smith Engl. Fl., and observation.)

PO'PULUS L. Bractea to the flower of each sex laciniated in its terminal edge. Male flower consisting of a calyx, and 8 stamens at fewest; in many instances, many more. Female flower consisting of a calyx and a pistil. Leaves with the disk more or less oblate; and the petiole, in most, compressed in the part adjoining the disk. (T. Nees ab Esenbeck Gen. Pl. Fl. Germ. Ill., and observation.)

Consistently with Dr. Lindley's definition of a catkin, given in his Introduction to Botany, ed. 2., what, in the genus Salix, has been usually termed the scale or the calyx, and by Borrer, in the Supplement to English Botany, the calyx scale, is here denominated a bractea; and what used to be called the nectary is, agreeably with Dr. Lindley's definition, in his Synopsis of the British Flora, here termed a gland.

GENUS I.

SALIX L. THE WILLOW. Lin. Syst. Diœ'cia Diándria.

Identification. Lin. Gen., 514.; Juss., 408.; Smith in Rees's Cyclo., vol. 31.; Fl. Br., 1039.; Tourn., t. 34.; Lam., t. 802.; Gærtn., t. 90.

Synonymes. Harab, Hebrew; Itea, Gr. ; Sàlix, Lat.; Saule, Fr.; Weide and Felber, Ger,; salcio, Ital.; Sauze, Span.; Wide, Swed.; Wilge, Flem.; Withig, Anglo-Sax.; Willow, Withy, Sallow, Osier, Engl.; Saugh, Scotch.

Derivation. From sal, near, and lis, water, Celtic; in reference to its general habitat. According to others, from salire, to leap; on account of the extraordinary rapidity of its growth.

Description, &c. Trees and shrubs, mostly the latter, varying from 2 in. or 3 in., to 50 ft., 60 ft., and even to 80 ft. or 90 ft. in height. The branches are round and flexible. Leaves simple, undivided, stalked, generally alternate, deciduous. Stipules in pairs at the base of the footstalks, very variable in size, deciduous. The leaves are arranged spirally on the branches; those on which 3 complete the spiral have the epithet tripla applied to them; those which have 4, tétrapla, &c. In a very few species only are the leaves placed opposite, and not in a spiral order. In by far the greater number they are disposed in a hexaplous order. (Walker.) Catkins early, erect or drooping,

either from the same buds as the leaves, or, more commonly, from different ones. Their florets are almost invariably separated, being all barren on one plant, and fertile on another of the same species. The growth of the dwarfest species, such as S. herbàcea, is slow, and, in its native habitat, not above 1 in. a year, and often not so much; that of the larger shrubs, in their native habitats, varies from 5 in. or 6 in. to as many feet, especially when the plants are young, or newly cut down. The growth of some of the kinds cultivated for basket-making or hoops, in good soil, when cut down every year or every two years, is often from 8 ft. to 12 ft. in a single season. The growth of the tree kinds, more especially of S. álba and S. Russelliana, is equally rapid when young; so that in ten years, in the climate of London, in suitable soil, and within reach of water, these kinds will attain the height of 50 ft. or 60 ft. The branches of most of the tree kinds have an upward direction, and have a flame-like motion in the wind, as in S. álba; but in others they are spreading, as in S. càprea; and, in one instance, drooping in a very decided manner, as in S. babylónica.

Anomalies in the Flowers. The flowers have been observed in various cases of anomaly, as to the manner in which they are disposed, or as to the constituent parts of themselves. A collection of cases and instances is here presented. Male flowers and female ones have been observed to occur in the same catkin in the following instances: S. Hoppeana Willd., as noticed in Willd. Sp. Pl., in Koch's Comm., and in Smith's Engl. Fl.; S. undulàta Ehrh., or else S. No. 37. of Treviranus's Obs. Bot.; S. mirábilis Host's Sal. Austr., i. t. 41.; and S. cinèrea, S. aurìta, and S. aquática, as noticed in Engl. Fl. Koch has noticed (Comm.) two instances under his S. cinèrea, which is more comprehensive than that of Engl. Fl.; S. càprea, as noticed by Koch, and taking the species as he views it; S. Humboldtiana, as noticed in Koch Comm.; S. tenuiflòra, as noticed in Host's Fl. Austr., ii. p. 633.; and S. Forbyàna, as noticed in Engl. Fl. The following cases are similar to the above, but some of the flowers are in a monstrous state : S. cinèrea, as noticed in Engl. Fl.; S. aquática, as noticed in Rees's Cyclo., No. 118.; and S. montàna Host Sal. Austr., i. t. 73. The appearance of stamens being changed into pistils has been observed in the following species:- S. hermaphrodítica L., as noticed in Koch's Comm.; S. Croweana, as elucidated in Sal. Wob.; S. polymorpha of Host's Sal. Austr., as shown there; S. oleifòlia Sm., as noticed in Engl. Fl.; and S. bicolor Ehrh., as cited by Borr. in Engl. Bot. Suppl. S. Hoppeȧna, besides having the majority of its catkins constituted partly of male flowers and partly of female ones, has, in some instances, in the upper flowers of a catkin, the middle one of the three stamens of a flower changed into a perfect ovary; and, hence, the flower seems as if comprising two stamens and an Ovary. (Koch's Comm.) Smith has noticed what may be a distinct case; viz. that in S. frágilis the stamens are not unfrequently accompanied by an imperfect pistil. (Engl. Fl.) The combination of the filaments, in some kinds, is a relative subject. Mr. Borrer considers the instance observed in S. Croweana a monstrosity. (Engl. Bot. Suppl., t. 2655.) He adds that the stamens are represented as changing into " ovaries, " as those of S. bicolor Ehrh., and of some of the common sallows, have been observed to do." It is likely that Mr. Borrer would apply the same remark to every instance of the filaments occurring in a state of combination. The following is a list of kinds in which the filaments have been observed in this state; and the practical cultivator may instruct himself by investigating, relatively to the above remark, as many of the following species as may come under his notice when in flower: S. rùbra Huds., noticed in Eng. Fl.; S. cóncolor of Host's Sal. Austr. (whether this be the same as the S. rùbra Huds., as the synonyme cited under it indicates, or different); S. Croweana in Eng. Fl.; S. ripària, as shown in Host's Sal. Austr., i. t. 58.; S. lineàris Forbes, as depicted in Sal. Wob.; S. intermèdia of Host's Sal. Austr., i. t. 56., as shown there; S. parviflòra Ibid., i. t. 49.; S. díscolor Ibid., i. t. 60.; S montàna Ibid., i. t. 73. f. 4.; S. lanàta L., as shown in Eng. Bot. Suppl.; and S. cladostémma of

Hayne Dendr., as cited in Koch Comm. It seems that Koch (Comm.) and Lindley (Synops. Brit. Fl.) view the kinds of the group Purpurea which have only 1 stamen to a flower, as having that stamen constituted of 2 combined. Besides the kinds of that group treated of in our work, exclusively of S. rubra, which may be examined as to the testing of this view, S. oppositifolia of Host's Sal. Austr., i. t. 38.; S. austriaca Ibid., i. t. 64.; S. montana Ibid., i. t. 73. f. 5.; and S. monandra Ibid., i. t. 71., may also be inspected.

The Sexes. Botanists seem to differ in opinion, as to the influence which the sex has upon the character, or appearance, of the plants. Dr. Walker says that "the male and female, of the same species, often differ remarkably from each other in their foliage;" and he instances the S. álba L., in the female of which, he says, "the leaves are much larger, greener, and not so white, silvery, and pubescent, as those of the male. This makes the difference in their aspect so great, he says, that, when standing together, they might, at first view, be presumed to be different species. In general," he adds, "the female of most plants is of more vigorous growth, of larger size, and less brittle, than the male; and," therefore, "the female ought always to be preferred when the species is to be cultivated for economical purposes that require strength; and the male for those which require delicacy." (Essays, p. 420.) Sir J. E. Smith is of a very different opinion from Dr. Walker, asserting that between a male and a female plant of the same species "there is not the slightest possible difference in the character or appearance of the two individuals, in any other respect" than in their flowers. (Eng. Flor., vol. iv. p. 163.) Most other botanists seem to incline more to the opinion of Dr. Walker, than to that of Sir J. E. Smith (see Desfontaines's Histoire, &c., vol. ii. p. 460; N. Du Ham., vol. iii. p. 104., &c.); and it is only necessary to turn over the figures of the splendid work of Host, in which engravings, a foot or two in length, are given of the male and female of every species, to be convinced that the view taken by Dr. Walker is correct. The importance, then, of knowing to what sex any species of willow belongs that we intend to cultivate for use is obvious. It appears, also, from Dr. Host's work, that the colour of the young wood, in the one sex, often differs from that of the other; for example, the young shoots of S. álba, female, are not only stronger, and the leaves broader, than those of the male, but the bark is of a dark red; while the young wood of the male is of a whitish green.

Hybrids. The production of hybrids in this genus was observed by Scopoli in 1760, and has since been confirmed or admitted by most other botanists. "The great number of hybrids in this genus," Koch observes, “no one can deny." (p. 9.) Sir J. E. Smith, however, formed quite a different opinion. During the thirty years that he studied the willows in Mr. Crowe's garden, along with that botanist, "seedlings innumerable," he says, "springing up all over the ground, were never destroyed till their specics were determined, and the immutability of each verified by our joint inspection. This was the more material, to set aside the gratuitous suppositions of the mixture of species, or the production of new or hybrid ones, of which, no more than of any change in established species, I have never met with an instance. Strange alterations in the shapes and sizes of leaves, and their stipules, have, indeed, been seen on young radical shoots, from a tree or bush that has been filled; but not more than usually happens in poplars, limes, elms, and others." (Eng. Fl., iv. p. 165.) It is much to be wished that some cultivator of willows would endeavour to originate, scientifically, some hybrids between species with opposite characters of foliage, which would set this question

at rest.

Geography. The willows are chiefly natives of the colder parts of the temperate regions of the northern hemisphere. They are generally found in cold moist soil, or by water; the trees on plains, and the creeping or trailing sorts on heaths and mountains. A few species are natives of the arctic circle; and S. herbacea and S. árctica approach nearer to the pole than any other ligneous plants. S. baby lónica is a native of Armenia, and also of China and Japan;

and Royle mentions several species as indigenous both to the lowlands and mountainous regions of Northern India. S. pedicellata Desf. and S. babylónica are found wild in the north of Africa; and S. Humboldtiana and S. Bonplandiana on the mountains of Peru and Columbia. The species indigenous to North America are not very numerous; but Pursh has described 37 sorts, as either wild or in a state of cultivation there. The number of species in different countries, however, cannot at present be determined with anything like accuracy, since what are considered as species by some botanists are looked upon as only varieties by others. Thus, Schleicher finds 119 species within the narrow limits of Switzerland; Host, 60 species natives of Austria; and Smith, and other British botanists, 71 species indigenous to Britain. Koch, however, the latest, and, as it appears to us, the most judicious, writer on the genus Salix, considers that all the alleged species, natives of Europe, may be reduced to 48. Perhaps, in addition to these, there may be a dozen natives of North America, which are not natives of Europe; and half that number natives of Asia. Of 182 species described by botanists, Koch observes, 17 only are extra-European.

History. Theophrastus and Pliny speak of different sorts of willows; the latter describing 8 species, as among the most useful of aquatic trees, not even excepting the poplar and the alder. The willow, Pliny says, furnishes long props for supporting vines, and the bark may be employed for tying up the shoots; and the young shoots, he adds, are much employed in basket-making. The kinds which the Romans used for this purpose appear, from Pliny's descriptions, to have been the S. álba, S. vitellina, S. viminalis, and the S. amerina of Pliny and Dalechamp, which was probably, as Dr. Walker thinks, the white willow of Theophrastus, and is certainly the S. decipiens L. These kinds formed the osier holts of the Romans, and are still those principally cultivated for basket-making, throughout Europe and North America, in the present day. Among modern botanists, the Bauhins, in 1650, first began to distinguish willows by their magnitude, the shape of their leaves, and by the nature of their flowers and fruit: and these authors were also the first to recognise in each species a fertile and an unfertile individual; and, with Tragus, to assert that willows could be propagated from seed, like other plants; a fact that had been denied since the days of Aristotle. Scopoli, in his Flora Carniolica, published in 1760, relates that he had often observed female willows fecundated by males which are accounted of a different species; and, if this observation is correct, it will help to account for the great number of kinds which compose this genus. The scientific botanical history of the willow may be considered as commencing with Ray's Synopsis, in 1660, in which he describes 10 species as growing in the neighbourhood of Cambridge. Linnæus, in 1737, described, in the Flora Lapponica, 19 species, chiefly alpine kinds; and in the second edition of his Species Plantarum, published in 1753, 31 species. Haller, in 1758, described 21 species as natives of Switzerland; and Villars, in 1789, 30 species as natives of Dauphiné. Willdenow, in his edition of Linnæus's Species Plantarum, published in 1797, describes 116 species. Smith, in Rees's Cyclopædia, published in 1819, describes 141 species; to which Willdenow and other botanists have since added, according to Koch, 41 species more, making in all 182; adding to these Schleicher's 119 new species, the total number is 254! In 1785, Hoffmann published the first fasciculus of his elaborate History of Willows, the last fasciculus of which came out in 1791; but the work was never completed. In so far as it goes, it is a splendid work; and one which can scarcely be surpassed either for accuracy or beauty. In 1828, Professor Koch, director of the botanic garden at Erlangen, published his De Salicibus Europæis Commentatio, an admirable work, of which a more particular account will be given here after; in which he has reduced all the European sorts, amounting, as we have just seen, to 237 (17 of the 254 being extra-European), to 48 species, belonging to 10 groups. Subsequently to the appearance of Koch's work, Dr. Host, director of the Flora Austriaca Botanic Garden at Vienna, published his Salir; of which only the first volume ap