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Show 360 CUCURBITACEOUS PLANTS-TREES. CHAP. X'. of mclonA in which the fruit is so like that of tho cucumber, "both externally and 'internally, that it is hardly possible to distinguish the one from tho other except by tho leaves." 'rhe varieties of the melon seem to bo endless, for Naudin after six years' study l1as not como to the c~d .of i110~: ho divides them into ten sections, including numerous sub-vanetJes '~luch all intercross with perfect ease. 143 Of the forms considered by Naudm to be varieties botanists have made thirty distinct species ! " and they had not the sligl~tcst acquaintance with the multitude of new forms wh!ch ha~·o appeared since thci1· time." Nor is tho creation of so many spccJCs ~tall surprising when we consider bow strictly their characters a~·c tra11sm~ttcd by seed and how wonderfully they differ in appcar::mcc : "M1.ra Cl:it qmdcnn folioru~ ot habitus divcrsitas, sccl multo magis fructuum," says Naudin. Tho fruit is tho valuable part, and this, in accordance with the common rule, is the most modified part. Some melons arc only as largo as small plums, others weigh as much as sixty-six pounds. One variety ha~ a scarlet fruit! Another is not more than an inch in diameter, but somet1mcs more than a yard in length, "twisting about in all directions like a serpent." It is a singular fact that in this latter variety many parts of the plant, namely, the stems, tho footstalks of the female flowers, the middle lobe of the leaves, and especially tho ovarium, as well as tho mature fruit, all show a strong tendency to become elongated. Several varieties of the melon arc interesting from assuming tho characteristic features of distinct species and even of distinct though allied genera : thus tho serpent-melon bas some resemblance to the fruit of 'l'riclwsanthes cwguina ; wo have seen that otl1cr varieties closely rcscmblo cucumbers; some Egyptian varieties have their seeds attached to a portion of tho pulp, and this is characteristic of certain wild forms. Lastly, a variety of melon from Algiers is remarkable from announcing its maturity by "a spontaneous and almos,t sudden dislocation," when deep cracks suddenly appear, and the fruit falls to pieces; a11d this occurs with the wild 0 . n.omonlica. Finally,~'[. Naudin well remarks that this "extraordinary production of races and varieties by a single species, and their permanence when not interfered with by crossing, are ].Jltenomcna well calculated to cause reflection." UsEFUL AND 0nNA!IIEN1'AL TnEES. TnEES deserve a passing notice on account of the numerous varieties which they present, difl'cring in their precocity, in their manner of growth, foliage, and bark. Thus of the common ash (F·ra:rinus e:rcelsiur) tho catalogue of Messrs. Lawson of Edinburgh includes twenty-one varieties, some of which differ much in their bark; thoro is a yellow, a streaked reddishwhite, a purple, a wart-barked and a fungous-barked variety.144 Of hollies no less than eighty-four varieties are grown alongside each other in lVIr. Memoir on Cucumis in 'Annal. des Sc. Nat.,' 4th series, Bot. tom. xi. 1859, P· 5. 143 See also Sogcrel's 'l\femoi1·e,' p. 7. 14 1 Loudon's 'Arboretum et Fruticetum,' vol. ii. p. 1217. CHAP. X. TREES. 361 Paul's nurscry.14b In the case of trees, all the recorded varieties, as far as I can find OLlt, have been suddenly produced by one single act of variation. 'I'ho length of time required to raise many generations, and the little value sot on the fanciful varieties, explains how it is that successive modifications have not been accumulated by selection; hence, also it follows that we do not here meet with sub-varieties subordinate to varieties, and these again subordinate to higher groups. On tho Continent, however, where tho forests arc more carefully attended to than in England, Alp h. De Candollc Ha Rays that there is not a forester who docs not search for seeds from that variety which ho esteems tho most valuable. Our useful trees have seldom been exposed to any great change of conditions; they have not been richly manured, and the English kinds grow under tbcir proper climate. Yet in examining extensive beds of seedlings in nursery-gardens considerable ditlcrcnccs may be generally ob. ·crvcd in them; and whilst toming in England I have been surprised at the amount of difference in the appcamnco of the same species in our hedgerows aml woods. But as plants vary so much in a truly wild state, it would bo dillicult for even a skilful botanist to pronounce whether, as I believe to be the case, hedgerow trees vary more than those growing in a primeval forest. Trees when planted by man in woods or hedges do not grow whcro they would naturally be able to hold their place against a host of competitors, and arc therefore exposed to conditions not strictly natural: even this slight chango would probably suffice to cause seedlings raised from such trees to be variable. Whether or not our half-wild English trees, as a general rule, arc more variable than trees growing in their native forests, there can hardly be a doubt that they have yielded a greater number of strongly-marked and singular variations of structure. In manner of growth, we have weeping or pendulous varieties of the willo':', ash,. elm,. oak, and yew, and other trees ; and this weeping habit is sometJmcs mhcnted, though in a singularly capricious manner. In tho Lombardy poplar, and in certain fastigatc or pyramidal varieties of thorns, junipers, oaks, &c., we have an opposite kind of growth. The Hessian oak/47 which is famous from its fastigato habit and size, bears hardly any 1·csemblanco in general appearance to a common oak · "its acorns arc not sure to produce plants of tho same habit· some h~wever turn out the same as tho parent-tree." Another fastigat~ oak i; said to h~vo been found wild in the Pyrenees, and this is a surprising circumstance; it generally c?mcs so t~·uo ~y ~cod, that De Candollo considered it as specifically distmct. 1'18 The fasbgato Juniper (.J. suecica) likewise transmits its character by sccd.149 Dr. Falconer informs mo that in the Botanic Gardens at Calcutta the great heat causes apple-trees to become fastigate; and wo HS 'Gardener's Chronicle,' ISGG, . 1006. p H 6 'Gcoo-mph. Bot.,' p. IODG. H7 'Gardener's Clu·on.,' 1842, p. 3G. 148 Loudon's 'Arbor tum et Fruticctum,' vol. iii. p. 17::!1. 149 Ibid., vol. iv. p. 2489. |