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Show 320 FERTILITY OF CROSSED CtrAP. IX. These cases show us how greatly superior i~. innate fertility tho seedlings from p~ants solf-fert1hsed or · tercrossecl for several gen rations and then crossed Iblyl a fresh stock are, in compan.s ~n w.i t.h t h e sec dl'm gs from plants of the old stock, either 1ntor~rosse~ or self-fertilised for the same nunlber of generatiOns. rhe three lots of plants in each ca e we:o loft free~y ex-osed to the visits of insects, anJ thou flowers Without Xoubt w8re cross-fertilis d by th n1. This table furth r shows u that in all four cases the intercrossed plants of th same .stock . s~ill have a decided though small a lvantage 1n fertility over the self-fertilise<l plants. 'Vith respect to the state of the reproductive organs in the self-f rtilis d plants of the two last tables, only a few obs rvations were macl . In the s~venth and eiahth o·enoration of Ipon1 a, tho anthers In the flowersbof th b solf-f rtilisoclr lants wore plainly smaller than those in th flower of th intcrcrossed plants. The tendency to sterility in th . ·o sainc plants was also shown by the first-form d flow r , after th~y had been carefully f rtilis d, fton dropping off, In the same manner as fr quently o curs with hybrids. The flowers likewi e tended to be 1nonstrous. In the fourth gen rati.o n of I) etuni.a , th e Po llcn produced by the self-f rtilis d and intorcr s eel plan~s wads compared, and th re were f.a r 1nor' e mnp t Y(o .~ nd shnvelle grains in the former. Relative Fe?"tility of Flowers cross d with Pollen frod~ a . . . 1 · 1J zz This hea wg d~st~nct Plant and wdh t w~r own o en. d includes flowers on the Pcwent-plants, an d on thed .c rossGee · and seljjertil,isecl Seedlings of the jiTst m· ct s·uccee tngh. h nerat~. on.-I WI' ll fi rst tr a t of ' th o p·(.1 rent-plants, w IC CHAP. IX. AND SELF-FERTILISED FLOWERS. 321 were raised from seeds purchased from nursery-gardens, or taken from plants growing in 1ny garden, or growing wild, and surrounded in very case by many individuals of the same Hpecies. Plants thus circuinstanced will co1nmonl y have been in tercrossecl by insects; so that the ~oedlings which were first experimented on will generally have been the product of a cross. Consequently any difference in the fertility of their flo\vers, when crossed and self-fer. tilised, will have been eaused by the nature of the pollen employed; that is, whether it was taken fron1 a distinct plant or fro1n the same flower. The cl - grees of fertility shown in the followinO' table F were determined in each case by the averab ge num' ber' of seeds per capsule, ascertained either by countino' or weighing. Another ele1nent ought properly to have been taken into account, namely, the proportion of flowers which yielded capsules when they were crossed and self-fertilised; and as crossed ·flowers generally produee a l?1:ger proportion of capsules, their superiority in fertility, 1f this ele1nent had been taken into account, would have been n1uch more strongly marked than appears in Tab]e F. But had I thus acted, there woul.d have been greater liability to error, as pollen apphed to the stig1na ·at the wrong time fails to produce any effect, independently of its greater or less potency. A good illustration of the great differencp I~ the results which sometimes follo,vs, if the number of c~~sules produced relatively to the nuiuber of flower fert1hsed be included in the calculation, was afforded ~[ N_olana prostrata. Thirty flowers on some plants tins species were crosseu and prod need twenty -seven capsules, each containing iive seeds; thirty-two flowers on the Saine plants were self-fertili~ecl and produeed y |