Excluding the seven cases
now referred to, there remain twenty-six in which the crossed plants
were manifestly much more fertile, sometimes to an extraordinary degree,
than the self-fertilised with which they grew in competition. The most
striking instances are those in which plants derived from a cross with a
fresh stock are compared with plants of one of the later self-fertilised
generations; yet there are some striking cases, as that of Viola,
between the intercrossed plants of the same stock and the
self-fertilised, even in the first generation. The results most to be
trusted are those in which the productiveness of the plants was
ascertained by the number of capsules produced by an equal number of
plants, together with the actual or average number of seeds in each
capsule. Of such cases there are twelve in the table, and the mean of
their mean fertility is as 100 for the crossed plants, to 59 for the
self-fertilised plants. The Primulaceae seem eminently liable to suffer
in fertility from self-fertilisation.
The following short table, Table 9/E, includes four cases which have
already been partly given in the last table.
TABLE 9/E.--INNATE FERTILITY OF PLANTS FROM A CROSS WITH A FRESH STOCK,
COMPARED WITH THAT OF INTERCROSSED PLANTS OF THE SAME STOCK, AND WITH
THAT OF SELF-FERTILISED PLANTS, ALL OF THE CORRESPONDING GENERATION.
FERTILITY JUDGED OF BY THE NUMBER OR WEIGHT OF SEEDS PRODUCED BY AN
EQUAL NUMBER OF PLANTS.
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