Pedigree of the mutative products of _Oenothera lamarckiana_ in
the Botanical Garden at Amsterdam. Laws of mutability. Sudden and
repeated leaps from an unchanging main strain. Constancy of the new
forms. Mutations in all directions.

XX. Origin of wild species and varieties. 576
Problems to solve. _Capsella heegeri_. _Oenothera biennis cruciata_.
_Epilobium hirsutum cruciatum_. _Hibiscus Moscheutos_. Purple beech.
Monophyllous strawberries. Chances of success with new mutations.

XXI. Mutations in horticulture. 604
_Chelidonium majus lacinatum_. Dwarf and spineless varieties.
Laciniate leaves. Monophyllous and broom-like varieties. [xvi] Purple
leaves. _Celosia_. Italian poplar. Cactus dahlia. Mutative origin of
_Dahlia fistulosa_, and _Geranium praetense_ in the experiment-garden.

XXII. Systematic atavism. 630
Reappearance of ancestral characters. _Primula acaulis umbellata_.
Bracts of crucifers. _Zea Mays cryptosperma_. Equisetum, _Dipsacus
sylvestris torsus_. Tomatoes.

XXIII. Taxonomic anomalies. 658
Specific characters occurring in other cases as casual
anomalies. _Papaver bracteatum monopetalum_. _Desmodium gyrans_ and
monophyllous varieties. Peltate leaves and ascidia. Flowers on
leaves. Leaves. _Hordeum trifurcatum_.

XXIV. Hypothesis of periodical mutations. 686
Discovering mutable strains. Periods of mutability and constancy.
Periods of mutations. Genealogical trees. Limited life-time of the