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Show 272 SUMMARY OF MEASUREMENTS. CHAP. VII. be crossed with intercrossed plants of the sa1ne stock with little or no advantage, although they profited to afl extraordinary degree by a cross with a fresh stock. With respect to the g~eater number of th: plants in Table A, nothing special need here be sa1d ; full particulars may be found under the heacl of each species by the aiel of the Index. The :6 gurcs in the rio·ht-hand column show the n1ean height of tho selffe~ tilised plants, that of the crossed plants wjth wh~ch they competed being represente~ by ~00. No notice is here taken of the few cases 1n w h1ch crossed and self-fertilised plants were grown in the open ground, so as not to co1npete together. The table includes, as we have seen, plants belonging to fifty-four species, but as soine of these were measured during several successive generations, there are eighty-throe cases in which crossed and self-fertilised plants wore compared. .A.s in each generation the nun1b r of plants which were 1neasured ( o·iven in the table) was never very large and sometimes 6 small, whenever in the right-hand column the mean heio·ht of the crossed and self-fertilised plants is the sa1ne ;ithin .five per cent., t~eir heights may be considered as practically oq nal. . Of such cases, that is, of self-fertilised plants of which tho mean hei()'ht is expressed by figures between 95 and 105, thetr<e are ei. ghteen, ei. th er I. n some one or. 'a ll tl1 ·0 oo· one-rations. rfhere arc eight cases in 'Which the ~elffertilised plants exceed the crossed by above five per cent., as shown by the figures in the right-hand column being above 105. Lastly, there are fifty-sev~~ cas:s in which tho crossed plants exceed tho solf-fort1hsed m a ratio of at least 100 to 95, and generally in a much higher degree. . T d If the relative heights of the erossed and self-forti 18e plants had been due to mere chance, there woulJ have CHAP. VII. TABLE A. 273 been about as many cases -of self-fertilised rlants exceeding the crossed in height by above five per CE}nt. as of the crossed thus exceeding the self-fertilised; but we see that of the latter there are fifty-seven cases, and of the former only eight cases; so that the cases in which the crossed plants exceed in height the selffertilised in the above proportion are more than seven tilnes as numerous as those in which the self-fertilised exceed the crossed in the same proportion. For our special purpose of comparing the powers of growth of crossed and self-fertilised plants, it may be said that in fifty-seven cases the crossed plants exceeded the self-fertilised by more than five per cent., and that in twenty-six cases (18 + 8) they did not thus exceed them. But we shall now show that in seveTal of these twenty-six cases the crossed plants h~d a decided advantage over the self-fertilised in other Tespects, though not in height; that in other cases the mean heights are not tTustworthy, owing to too few plants having been measured, or to their having grown unequally from being unhealthy, or to both causes con1Linod. Nevertheless, as these cases are opposed to 111 y general conclusion I have felt bound to give them. La ·tly, the cause of the crossed plants having no advantage over the self-fertilised can be explained in some other cases. Thus a very sn1all' residue is left in which tho selffertilised plants appear, a.· far as my experin1onts serve, to be really equal or superior to tho crosseJ plants. 'iV e will now consider in so1ne little detail the eighteen cases in which the self-fertilised plants equtt1Jed in average height tho crossed plants within five peT cent. ; and the eight cases in ·which the e]f-fertiJisod plants exceeded in average height the crossed plants by above five per cont.; n1aki11g altogether twenty-six 'l' |