ON SOME APPARENT AND REAL CAUSES OF ERROR IN MY EXPERIMENTS.
It has been objected to such experiments as mine, that covering plants
with a net, although only for a short time whilst in flower, may affect
their health and fertility. I have seen no such effect except in one
instance with a Myosotis, and the covering may not then have been the
real cause of injury. But even if the net were slightly injurious, and
certainly it was not so in any high degree, as I could judge by the
appearance of the plants and by comparing their fertility with that of
neighbouring uncovered plants, it would not have vitiated my
experiments; for in all the more important cases the flowers were
crossed as well as self-fertilised under a net, so that they were
treated in this respect exactly alike.
As it is impossible to exclude such minute pollen-carrying insects as
Thrips, flowers which it was intended to fertilise with their own pollen
may sometimes have been afterwards crossed with pollen brought by these
insects from another flower on the same plant; but as we shall hereafter
see, a cross of this kind does not produce any effect, or at most only a
slight one. When two or more plants were placed near one another under
the same net, as was often done, there is some real though not great
danger of the flowers which were believed to be self-fertilised being
afterwards crossed with pollen brought by Thrips from a distinct plant.
Pages:
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57