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Show 324 DARWINISM CHAP. - . se is to a.ttract insects, they could and as the chwf us~ of .th?. . flowers 1 vV e know, moreover, hardly ha.ve existed m prlmltlveb i~·ed for the a.ttraction of h th etals cease to e requ that w en e p . . 0 0 ° if }'/oml .Stmctw·es, :says : H ·l v m his ngtn o d t' 1 The Rev. George ens O\ l'l . l fertilised ·mcriosperms are degra a lOlls "There is little doubt but that a wm~; t . '1t?n s~nfjltisorbct is ancmophilo.uR ; from insect-fertilised _flo,~er . .. ··u·m·abl o~; s so formerly, but has reacqun·ell and Sangnisorba offw~?utl~s p1 e~ l trfbe Poteriere being, in fnet, a .degradctl an entomophilous habit; the" lO e t'llere Plantains retain thetr (;Orolla. ~roup which has des ended from Potet~ I aded Lilies. while Cyperaccc' :uHl but in a degraded form. Juncero are e~ anked with Ameniiferre amollg Graminere among monocot~ledo~s ~~a~hi~l rhave retrograded very far from dicotyledons, a. representmg or~l~l ~ they wei·e possibly and ]Jrohably \lethe entomophilous forms from w uc l scemled" (p. 266). . l lictnt?n minus Poterium, and others, well "'rhe genus Plantago, like T ~a 1 .1 us 'to the anemoplulous st ate. i1lustrate the change f rom. 'a n entomopd ni ov isited by pollen-seek.m g m. scc·L s, P la?tceolata ha. polymorphtc Hower:, ant . tlle 'vind P. meclict illu strates . ']' 1 'tl e by 111 ec s or . I so that it can be fertl I ·cc et 1 r tl filaments are pink, the an tlers transitions in point of struct~rc, as ~:ted and it is regularly vi ·ite\l hy motionle s, and the pollen grat·nls a~grt~ge .le:tder filaments, v •rsatilc an t h e~·~, Bombus terrestris. On the othei 1atnt' 1 s style are feature . of other spct:tes l)owdery l)Ollen, allC1 e Io n",,' \ted. pro oc0 rynou f n <d egraded COI'Ol l a i'l lO W:>. I' lS· 1 .1 . h 'le the presence o •• ' . indicating anemop 11 Y ' w 1 1 .1 p medict therefore, tllustrates, no · ance tors to have beet.l entomo}J~~ o~t\ut ~ returt~ to it; just as is the cast> a primitive entomOJ~h.llou~ cond~~~i~ Caprect; ])ut these show no capac tty ol with Sanrmisorba oj}wmal~s and. c " t res having to be borne by the l'aly-x, restoring "t he c?ro1 1. a, t.l1 e att.r actbi Veb 1 eat hue p· ink' ftlaments of Plantago, ancl 1> y which is purpltsh Ill angm. or a, 'll " (p 271) the yellow anthers i~ the Sallo:t . Wl l ~w lfer ~f inc~nspicuousness and all !duels "The interpretatwn, then, wot~ c ot tl t of couspicuousues aiHl great of degradations is the exact oppost~e o ith1aminute liowers, rarely or Jlever differentiations ; namely, ~hat spe~~~~fe~\ilisecl, have priwarily arisen through visited by insects, and habttually .s Jence assumed their present llural the neglect of insects, and have m conseqt .. structures " (p. 282). . . Renslow he gives a few aclchlwnal In a letter ju~t r~cetvetl frott lM~l~e followit~g are the most import:mt; illustrations of Ius vtews, of '\.:~~;s known collectively a . '. Cyclospcm.IIC·~" . "Passin" to Incomplet::e, the o . 'n<l arc decrradatwns from Jt, of ' 0 I j ll ' and tO my Ill! ' O < l ]' are related to ~aryop 1Y ~re ' ' C uliferro lJavc an inferior ovary anc .n1' 1 which Orache IS anemophtlous. Tulp "'S fat· as I know cannot J,e llllt·r- . b th top 1ese, ... , • . ' t • mentary calyx-ltm on ~ · 1 h 1 of Monocotylcclons appear 0 lllt preted except as degradatwns .. T Je ~o ob: degradations from Dicotyledous, (from anatomical reasons especJally)f rowth in water. Many subsequently and primarily through the .ager·: oeff~cts of their primitive habitat t h.rough became terrestrial, but retam~c tl e f ·ses the l)arts of the flower belllg Ill · Th 3 rous penant 1 o gra. · ' . . , herecltty e -me . f· m a sub-liliaceous colHhtwn. . whorls, point to a tlegradattol~ Itol ,h. long held the ·e views, but, as frtr ~~~ Mr. Henslow informs met a 1e as . t forth a similar theory in ln$ he knows alone. Mr. Grant Allen, howeverf, lsl . "'he Colmt'l'S nl FluwcJw ) ( 15) and more u y 111 J L ' r Vignettes j'l'O?n Ncttttre p. ·t f 11 and uses similar arguweuts to those o (chap. v.), where he clevelops 1 u Y Mr. Renslow. xr THE SPECIAL COLOURS OF PLANTS 325 insect , they rapidly diminish in size, lose their bright colour or a.lmo t wholly disa.ppear.1 Difficulties and Contmdict'ions. The very bare summary that has now been given of the main fa.cts rela.ting to the fertilisation of flowers, will have served to show the vast extent and complexity of the inquiry, and the extraordinary contradictions and difficulties which it presents. We ha.ve direct proof of the beneficial results of intercrossing in a great number of cases; we have an overwhelming rna. s of facts as to the va.ried and complex structure of flowers evidently adapted to secure this intercrossing by insect agency ; yet we see many of the most vigorous plants which spread widely over the globe, with none of these adaptations, and evidently depending on self-fertilisation for their continued existence and success in the battle of life. Yet more extraordinary is it to find numerous cases in which the special armngements for cross-fertilisation appear to have been a failure, since they have either been supplemented by special mea.ns for self-fertilisation, or have reverted back in various degrees to simpler forms in which self-fertilisa.tion becomes the rule. There is al o a further difficulty in the highly complex modes by which cross-fertilisation is o(ten brought about; for we have seen that there are several very effective yet very simple modes of securing intercrossing, involving a minimum of cha.nge in the form and structure of the flower ; and when we consider that the result attained with so much cost of structural modification is by no means an unmixed good, and is far less certain in securing the perpetuation of the species than is self-fertilisation, it is most puzzling to find such complex methods resorted to, sometimes to the extent of special precautions against the possibility of self-fertilisation ever taking place. Let us now see whether any light can be thrown on these various anomalies .and contradictions. Intetc1·ossing not necessa1·ily Advantageous. No one was more fully impressed than Mr. Darwin with the beneficial effects of intercrossing on the vigour and fertility 1 H. Mi.iller gives ample proof of this in his Fertilisation of Flowe?"S. |
