After the crossed or the self-fertilised plants had once grown decidedly
taller than their opponents, a still increasing advantage would tend to
follow from the stronger plants robbing the weaker ones of nourishment
and overshadowing them. This was evidently the case with the crossed
plants of Viola tricolor, which ultimately quite overwhelmed the
self-fertilised. But that the crossed plants have an inherent
superiority, independently of competition, was sometimes well shown when
both lots were planted separately, not far distant from one another, in
good soil in the open ground. This was likewise shown in several cases,
even with plants growing in close competition with one another, by one
of the self-fertilised plants exceeding for a time its crossed opponent,
which had been injured by some accident or was at first sickly, but
being ultimately conquered by it. The plants of the eighth generation of
Ipomoea were raised from small seeds produced by unhealthy parents, and
the self-fertilised plants grew at first very rapidly, so that when the
plants of both lots were about three feet in height, the mean height of
the crossed to that of the self-fertilised was as 100 to 122; when they
were about six feet high the two lots were very nearly equal, but
ultimately when between eight and nine feet in height, the crossed
plants asserted their usually superiority, and were to the
self-fertilised in height as 100 to 85.
Pages:
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419