Solche Merkmale waren für die Einzel-Versuche nicht verwendbar, diese konnten sich nur auf Charactere beschränken, die an den Pflanzen deutlich und entschieden hervortreten.
Such traits were unsuitable for the individual trials; these had to confine themselves to those characteristics that emerge clearly and decisively in the plants.
The sentence in the German original consists of two full sentences, separated by a comma. This was probably done to emphasise that the second sentence explains the strong statement of the first. Like Bateson and Sherwood, we have chosen to replace the comma by a semicolon.
characteristics = Charactere The sentence shows that Mendel is using Merkmal and Character synonymously; here, he chooses Character to avoid repetition. We translate this as “characteristics”, following Sherwood; for a different use of the term Character see p. 14, s. 1.
trial = Versuch See p. 3, s. 6.
had to = konnten … nur Literally this means “could … only”, and Bateson translates it like this. The expression is commonly used in German to express that something is without alternative, however, so we have followed Sherwood’s more elegant translation.