OCR Text |
Show 304: SILK-MOTIIS. CHAP. Vlll. moths, but tho disuse of thor. r wm. gs d un.·n g s0 many generations has, it may be suspected, likewise come into play. . to the surface on Tho moths of many breeds fail to gluo thou·d~ggs t C t Hutton 7>~ which they aro laid,77 but this proceeds, accor mg o ap . ' merely from the gland s o f· th0 ovi·p o sito. r being we·a k·et'n ecdt.s of the silk-moth As with other long-domesticated ammals, thde ms mm~lborry-tree often fii d Tl t . ·uars when place on a ' have su ere · 10 ~a orpi ·' .· h base of tho loaf on which they commit tho strange mistake of dovounng. t b~t tho aro capable, according arc feeding, and consequently fa~ down' th t . Jc Evon this capacity to M Robinot,19 of again crawlmg up 0 ru · . t. d •• • • • 80 laced somo caterpillars on a roo, an somot1mos fmls, for M. Mar tms P d . · h d of hunger · they those which fell woro not able to remount an pens o ' wore oven m· oapa blo . 0 f ssing from loaf to loaf. P~ . ilk- th has undergone stand in Some of tho moclificatwns which tho s m~ th oths which produce correlation with eo.ch other. Thus tho eggs 0 0 m difli . 1. btl l hi h produce yellow cocoons or s 1g y white cocoons and of t lose w c ·u hi h . ld h't in tint Tho abdomino.l feet also of tho caterpi ars w 0 Y10 w ~ e · h't h'l t those which give yellow cocoons arc m-cocoons arc always w I 0• w I s t . 'll ith dark tiger-like vario.bly yollow.s1 We havo soon that tho ca erpi ars w . d tl h. h . moro darkly shaded than other moths. stnpos pro ulclo mt obl:shwd~~ tharaot in France tho catorpillo.rs of tho races It seems we os a IS o · . h . .. t d whw· h pro d uco wh 't 'Jk d certo.in black caterpillars, o.vo ros1s o , I e Sl , an d t t d th better than other races, the disease which ~as. recently ovas a 0 0 silk-districts. Lastly, tho races differ constitutiOnally, for some ~o not succeed so well under a temperate climate as others ; and a damp sml docs not equally injure all tho races. 83 From these various facts we learn that silk-moths, l~ke :be higher animals, vary greatly unuer long-continu~d .domestiCation~ We learn also the more important fact that vanatwns may oc~ur at various periods of life, and be inherited at correspondmg periods. And finally we see that insects are amenable to the great principle of Selection. 77 Quatrcfagcs, 'Etudes,' &c., p. 214. 78 'Transact, Ent. Soc.,' ut supra, p. 151. 79 'Mnnuel de l'Educatcur,' &c., p. 26. ao Godron, 'De l'Espccc,' p. 4G2. 81 Quatrefagcs, 'Etudes,' &c., PP· 12, 209, 211. s2 Robinet, 'Manuel,' &c., p. 303. 8~ Robinet, idem, p. 15. CHAP. IX. CULTIVATED PLANTS. 305 CHAPTER IX. CULTIVATED PLANTS: CEREAL AND CULINARY PLANTS. PRELIMINARY REMARKS ON TilE NUMBER AND PARENTAGE OF CULTIVATED PLANTS - FIRST STEPS IN CULTIVATION - GEOGRAPHICAL DISTRIDU1.'ION OF CULTIVATED PLANTS. CEREALIA.- DOUBTS ON 'l'TIE NUMBER OF SPECIES. -- WHEAT: VARIETIES OF -INDIVIDUAL VARIABILITY- OllANGED llADITS- SELJ!!CTION- ANCIENT lliSTOUY 01<' TIIE VARIETlE ',--MAIZE: GREAT VARIATION OF- DIREC'£ ACTION OF CLIMATE ON. CULINARY PLANTS.- CABBAGES : VARIETIES OF, IN FOLIAGE AND STEMS, BUT NOT lN OTIIER !'ARTS- PARENTAGE OF- OTllER SPECIES OF BRASSICA. -PEAS: Ali10UNT OF DIFFERENCE IN 1.'HE SEVERAL KINDS, CHIEFLY IN TilE PODS AND SEED- SOUE VARIETIES CONSTAN1.', SOME HIGHLY VARIADLE .-DO NOT lNTEUCROSS. --DEANS. --l'OTATOES : NUMEROUS VARIETIES OF- DIFFERING Ll'l'TLE, EXCEP'l' IN THE TUBERS- CllABAOTERS INllERITED. I SHALL not enter into so much detail on the variability of cultivated plants, as in the case of domesticated animals. The subject is involved in much difficulty. Botanists have generally neglected cultivated varieties, as beneath their notice. In several cases the wild prototype is unknown or doubtfully known; and in other cases it is hardly possible to distinguish between escaped seedlings and truly wild plants, so that there is no safe standard of comparison by which to judge of any supposed amount of change. Not a few botanists believe that several of our anciently cultivated plants have become so profoundly modified that it is not possible now to recognise their aboriginal parent-forms. Equally perplexing are the doubts whether some of them are desoenrled from one species, or from several inextricably commingled by crossing and variation. Variations often pass into, and cannot be distinguished from, monstrosities; and monstrosities are of little significance for our purpose. Many varieties are propagated solely by grafts, buds, layers, bulbs, &c., and frequently it is not known how far their peculiarities can be transmitted by seminal generation. Nevertheless some facts of value can be gleaned ; and other facts will hereafter be incident- VOL. I. X |