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Show 306 DARWINISM CH.\ 1'. by floating m. n.v crs and 1a 1 < :es, an d thu s reach. incbr other locali- 1 d ll ties Durin a- the elevation of land areas this met 10 ' 1 vou < be v• ery effecbti. ve, a.s t h e new 1a n d wou ld alwa. ys be at ha ofw e, r level than that alren,dy covered with vc?ctatwn, a~d t ~re ore in the best position for being stocked With plants ~fm ~~- The other moues of dispersal of seeds are so clear y a n,ptct 1 to thei. r spccw. l wants, t 11 :1 t we fe e 1 sure they must have b.e en ac uired by the process of variation and na.tural selectiOn. Tl{e hooked a.ncl sticky seeds arc a.lwa.ys_ th~se of such h _r-b 11nts as are likely from their s1ze, to come lll aceous p < • ' h · f ttl h ·1 contact with the wool of sheep or the aJr o ca e; w I .' seeds of this kind never occur on forest trees, ?n aqu;ttlc p 1a nts, or even On Very dwarf creer1crs or trmlcrs. 1T he wing cl seed-vessels or seeds, on the other hand, mostly be ong to trees a.n cl t o t a ll Shrubs or .c l.i mbe.r s · W c h· ave, theref1or e, af act a(la1)tation to conditwns m these different moe c. o very ex < · 'd · d' · 1 1 d1. sper, s a1 ., w h1'l e, when we come to cons1 or In IVf I<. uha · 1c ase1s , we find innumerable other adaptations, some o w _IC 1 t lC reader will find described in the little 'Work by Sn· J ohn Lubbock a.lready referred to. Edible or Attmctive F1·uits. It · s however when we come to true fruits (in a popular ) 1 sense t'h a. t we 'find varied colours evident1ly intended h ·t1o attract animals, in order that the fru~ts may )e eaten, w 1. c the seeds pass through the body un?1gested and are ~hen ~n the fittest stn,tc for germination. Th1s end has been gamed_ m a great variety of ways, and with so many corrcspondmg ooaptations as to leave no doubt as to the value of the resnlt. Fruits are pulpy or juicy, and usually sweet, and form the favourite food of innumerable birds and som.e mamm<.tls.. They are always coloured so as to contrast w1t~ .the fol~age nr surroundings, red being the most common as It 1s ccr ta.mly t!1e most conspicuous colour, but ye'llow, purple-, ~la.c_k, or wh1te being not uncommon. The edible portion of frmts IS develop~cl from different parts of the floral envelopes, or of the ovary, m the various orders and genera. Sometimes the cal y:'( becomes enlarged and fleshy, as in the apple and pear tn be; mo:·c often the integuments of the ovary itself arc. cnhrgccl, as m the plum, peach, grape, etc. ; the receptacle I. enlarged a.nu XI THE SPECIAL COLOURS OF PLANTS 307 forms the fruit of the strawberry; while the mulberry, pineapp. le, and fig are examples of compound fruits formed in vanous ways from a dense mass of flowers. In ~ll cases ~he seeds themselves are protected from injury by vanous deviCes. They are small and hard in the strawberry, raspberry, currant, etc., and are readily swallowed :among the copious pulp. In the grape they are hard and bi~ter; in t~e rose (hip) disagreeably hairy; in the orange tnbo. very ?1tter ; .. and all ~hese have a smooth, glutinous exterior wh10h fa01htates their being swallowed. When the seeds are larger and are eatable, they are enclosed in an excessively hard and thick covering, as in the various kinds of :'stone " fruit (plums, peaches, etc.), or in a very tough core, as m the appl~. In the ~utmeg o~ the Eastern Archipelago we have a curwus adaptatiOn to a smgle group of birds. The fruit is yellow, somewhat like an oval peach, but firm and hardly eat~ble. This splits open and shows the glossy black ?overmg of th~ seed or nut~cg, over which spreads the bnght scarlet anllus or "mace, an adventitious growth 'Of .no ~se to the plant except to attract attention. Large frmt pigeons pluck out this seed and swallow it entire for the sake of the mace, while the large nutmeg passes through their bodies and germinates; and this has led to the wide distribution of wild nutmegs over New Guinea and the surrounding islands. In the restriction of b:dght colour to those edible fruits the eating of which is beneficial to the plant, we see the undoubted result of natural selection ; and this is the more evident when we fir:d t~at the colour. ne.ve~ appears till the fruit is ripethat Is, till the seeds w1thm It are fully matured and in the best state for germination. Some brilliantly coloured fruits are pois~nous, as in our bitter-sweet (Solanum dulcamara), cuckoo-pmt (Arum) and the West Indian manchineel. Many 'Of these are, no. doubt, eaten by animals to whom they are harmless; and It has been suggested that even if some animals are poiso~ed by them the plant is benefited, since it not. onl! .gets d~spersed, but finds, in the decaying body of Its VICtim, a nch manure heap.I The particular colours <>f fruits are not, so far as we know, of any use to them other 1 Grant Allen's Colo~w Sense, p. 113. |