races of tricotyls and syncotyls. Selection by the hereditary
percentage among the offspring.

XV. Double adaptations. 430
Analogy between double adaptations and anomalous middle races.
_Polygonum amphibium_. Alpine plants. _Othonna crassifolia_. Leaves
in sunshine and shadow. Giants and dwarfs. Figs and ivy. Leaves of
seedlings.

E. MUTATIONS.

XVI. Origin of the peloric toad-flax. 459
Sudden and frequent origin in the wild state. Origin in the
experiment-garden. Law of repeated mutations. Probable origin of
other pelories.

[xv]
XVII. The production of double flowers. 488
Sudden appearance of double flowers in horticulture. Historical
evidence. Experimental origin of _Chrysanthemum segetum plenum_.
Dependency upon nourishment. Petalody of stamens.

XVIII New species of _Oenothera_. 516
Mutations of _Oenothera lamarckiana_ in the wild state near
Hilversum. New varieties of _O. laevifolia_, _O. brevistylis_, and
_O. nanella_. New elementary species, _O. gigas_, _O. rubrinervis_,
_albida_, and _oblonga_. _O. lata_, a pistillate form.
Inconstancy of _O. scintillans_.

XIX. Experimental pedigree-cultures. 547