Therefore in these several cases the crossing of plants, which had been
self-fertilised for several generations and which had been cultivated
all the time under as nearly as possible the same conditions, was not in
the least beneficial.
Another experiment was now tried. Firstly, plants of the eighth
self-fertilised generation were again self-fertilised, producing plants
of the ninth self-fertilised generation. Secondly, two of the plants of
the eighth self-fertilised generation were intercrossed 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 of self-fertilisation. Thirdly, the same plants of the
eighth self-fertilised generation were crossed with pollen from plants
of a fresh stock brought from a distant garden. Numerous plants were
raised from these three sets of seeds, and grown in competition with one
another. The plants derived from a cross between the self-fertilised
plants exceeded in height by a little the self-fertilised, namely, as
100 to 92; and in fertility in a greater degree, namely, as 100 to 73. I
do not know whether this difference in the result, compared with that in
the previous case, can be accounted for by the increased deterioration
of the self-fertilised plants from two additional generations of
self-fertilisation, and the consequent advantage of any cross whatever,
along merely between the self-fertilised plants.
Pages:
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386