The best coverings are of netting, or of
canvas of sufficiently wide mesh, although after a long experience I
greatly prefer cages of fine iron-wire, which are put around and over
the whole plant or group of plants, and fastened securely and tightly to
the ground.
[160] Paper bags also may be made use of. They are slipped over the
flowering branches, and bound together around the twigs, thus enclosing
the flowers. It is necessary to use prepared papers, in order that they
may resist rain and wind. The best sort, and the one that I use almost
exclusively in my fertilization-experiments, is made of parchment-paper.
This is a wood-pulp preparation, freed artificially from the so-called
wood-substance or lignin. Having covered the flowers with care, and
having gathered the seeds free from intermixtures and if possible
separately for each single individual, it only remains to sow them in
quantities that will yield the greatest possible number of individuals.
Reversions are supposed to be rare and small groups of seedlings of
course would not suffice to bring them to light. Only sowings of many
hundreds or thousands of individuals are decisive. Such sowings can be
made in one year, or can be extended over a series of years and of
generations. Hildebrand and Hoffman have preferred the last method, and
so did Hofmeister and many others.
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