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Show 260 SUMMARY OF MEASUREMENTS. CIIAP. VII. self-fertilised plants of the sixth generation had become 1nuch more fertile than the intercrossod plant ... , jU<lging Ly the number of capsules spontaneously produced, in the ratio of 147 to 100. This variety, which as we have seen appeared amongst the plants of the fourth self-fertilised generation, reseinblos in almost aH its constitutional peculiarities the vari ty called Hero which appeared in the sixth self-£ rtilised generation of Ipomooa. No other such case, with the partial exception of that of Nicotiana, occurred in my experiments, carried on during eleven y ars. Two plants of this variety of Mimulus, belonging to the sixth self-fertilised generation, and growing in separate pots, were in tercrossed ; and so1ne flowers on the same plants wore again se~f-fertilisecl. ~.,ron1 tho seeds thus obtained, plants derived from a cross Letween the self-fertilised plar.ts, and others of the seventh self-fertilised generation, were raised. But this cross did not do the least good, the intercrossed plants being inferior in height to the self-fertilised, in the ratio of 100 to 110. This case is exactly parallel with that given under Ipomcea, of the grandchildren of Hero, and apparently of its great-grandchildren; for the seedlings raised Ly intorcrossing these plants were not in any way superior to those of the corresponding generation raised from the self-fertilised flowers. ~rherefore in these several cases the crossing of plants, which had been self-fertilised for several generations and which had been cultivated all the ti1ne under as. nearly as possibl8 tho same conditions, was not in the least beneficial. Another experiment was now tried. Firstly, plan.ts of the eighth self-fertilised generation were agam self. fertilised, producing plants of the ninth selffer6lised generation. Secondly, two of the plants of the CHAP. VII. TABLE C. 2Gl eighth self-fertilised generation were intercrossecl one with another, as in the experiment above referred to; but this was now effected on plants which had been subjected to two additional generations o.f self-fertilisation. Thirdly, the same plants of the eighth selffertilised o-eneration were crossed with pollen from 0 . plants of a fresh stock brought fro1n a distant garden. Numerous plants wore raised fro In these three sets of seeds, and grown in competition with one another. The plants derived froin a cross between the self-fertilised plants exceeded in height by a little the selffertilised, viz., as 100 to 92; and in fertility in a greater degree, viz., as 100 to 73. I do not ~now w~ether this difference in the result, compared with that In the previous case, can be accounted for by the increasea deterioration of the self-fertilised plants fron1 two additional generations of self-fertilisation, and the consequent advantage of any cross whatever, although merely between the self-fertilised plants. But ho':~ver this rna y be, the effects of crossing the self-fert1hsecl Plants of the eio·hth generation with a fresh stock were extremely strik0i ng ; for the seedlings thus rai.s ecl wore to the self-fertilised of the ninth generation as 100 to 52 in height, and as 100 to 3 in fer~ility ! They w_cre also to the intercrossed plants ( denvecl from crossing two of the self-fertilised plants of the eighth generation) in height as 100 to 56, and in fert~lity as 100 to 4. Better evidence could hardly be desued of the potent influence of a cross with a fresh stock on plants which had been self-fertilised for eight. generations, and had been cultivated all the time under nearly unifonn conditions, in con1parison with plants self-fert~lisecl for nine generations continuously, ?r then once Intercrossed, na1nel y in the last generation. (3.) Brassica oleracea.-Some flowers on cabbage |