Schwache Exemplare geben immer unsichere Resultate, weil schon in der ersten Generation der Hybriden und noch mehr in der folgenden manche Abkömmlinge entweder gar nicht zur Blüthe gelangen, oder doch wenige und schlechte Samen bilden.
Weak specimens always give uncertain results, because already in the first generation of hybrids, and even more so in following ones, some descendants either come to flower not at all, or at least form few and poor seeds.
This statement is in the present tense, and hence rather summarises a general experience, rather than results from experiments that were carried out to ascertain the claim.
first generation = ersten Generation Refers to what we would call F2 today (see p. 12, s. 3).
offspring = Abkömmlinge Abkömmling has a slightly negative connotation of distant relationship and degeneration. In the early nineteenth century, it was also used for offshoots or scions by which fruit-trees in particular were reproduced vegetatively; see Jacob and Wilhelm Grimm, Deutsches Wörterbuch, online-edition, s.v. “abkömmling” (1852).