The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom | Page 4

of
plants.--Benefits derived from cross-fertilisation.--Self-fertilisation
favourable to the propagation of the species.--Brief history of the
subject.--Object of the experiments, and the manner in which they were
tried.--Statistical value of the measurements.--The experiments carried
on during several successive generations.--Nature of the relationship of
the plants in the later generations.--Uniformity of the conditions to
which the plants were subjected.--Some apparent and some real causes
of error.--Amount of pollen employed.--Arrangement of the
work.--Importance of the conclusions.

CHAPTER II.
CONVOLVULACEAE.
Ipomoea purpurea, comparison of the height and fertility of the crossed
and self-fertilised plants during ten successive generations.--Greater
constitutional vigour of the crossed plants.--The effects on the offspring
of crossing different flowers on the same plant, instead of crossing
distinct individuals.--The effects of a cross with a fresh stock.--The
descendants of the self-fertilised plant named Hero.--Summary on the
growth, vigour, and fertility of the successive crossed and self-fertilised
generations.--Small amount of pollen in the anthers of the self-fertilised
plants of the later generations, and the sterility of their first-produced
flowers.--Uniform colour of the flowers produced by the self-fertilised
plants.--The advantage from a cross between two distinct plants
depends on their differing in constitution.

CHAPTER III.
SCROPHULARIACEAE, GESNERIACEAE, LABIATAE, ETC.

Mimulus luteus; height, vigour, and fertility of the crossed and
self-fertilised plants of the first four generations.--Appearance of a new,
tall, and highly self-fertile variety.--Offspring from a cross between
self-fertilised plants.--Effects of a cross with a fresh stock.--Effects of
crossing flowers on the same plant.--Summary on Mimulus
luteus.--Digitalis purpurea, superiority of the crossed plants.--Effects of
crossing flowers on the same plant.--Calceolaria.--Linaria
vulgaris.--Verbascum thapsus.--Vandellia
nummularifolia.--Cleistogene flowers.--Gesneria pendulina.--Salvia
coccinea.--Origanum vulgare, great increase of the crossed plants by
stolons.--Thunbergia alata.

CHAPTER IV.
CRUCIFERAE, PAPAVERACEAE, RESEDACEAE, ETC.
Brassica oleracea, crossed and self-fertilised plants.--Great effect of a
cross with a fresh stock on the weight of the offspring.--Iberis
umbellata.--Papaver vagum.--Eschscholtzia californica, seedlings from
a cross with a fresh stock not more vigorous, but more fertile than the
self-fertilised seedlings.--Reseda lutea and odorata, many individuals
sterile with their own pollen.--Viola tricolor, wonderful effects of a
cross.--Adonis aestivalis.--Delphinium consolida.--Viscaria oculata,
crossed plants hardly taller, but more fertile than the
self-fertilised.--Dianthus caryophyllus, crossed and self-fertilised plants
compared for four generations.--Great effects of a cross with a fresh
stock.--Uniform colour of the flowers on the self-fertilised
plants.--Hibiscus africanus.

CHAPTER V.
GERANIACEAE, LEGUMINOSAE, ONAGRACEAE, ETC.
Pelargonium zonale, a cross between plants propagated by cuttings

does no good.--Tropaeolum minus.--Limnanthes douglasii.--Lupinus
luteus and pilosus.--Phaseolus multiflorus and vulgaris.--Lathyrus
odoratus, varieties of, never naturally intercross in England.--Pisum
sativum, varieties of, rarely intercross, but a cross between them highly
beneficial.--Sarothamnus scoparius, wonderful effects of a
cross.--Ononis minutissima, cleistogene flowers of.--Summary on the
Leguminosae.--Clarkia elegans.--Bartonia aurea.--Passiflora
gracilis.--Apium petroselinum.--Scabiosa atropurpurea.--Lactuca
sativa.--Specularia speculum.--Lobelia ramosa, advantages of a cross
during two generations.--Lobelia fulgens.--Nemophila insignis, great
advantages of a cross.--Borago officinalis.--Nolana prostrata.

CHAPTER VI.
SOLANACEAE, PRIMULACEAE, POLYGONEAE, ETC.
Petunia violacea, crossed and self-fertilised plants compared for four
generations.--Effects of a cross with a fresh stock.--Uniform colour of
the flowers on the self-fertilised plants of the fourth
generation.--Nicotiana tabacum, crossed and self-fertilised plants of
equal height.--Great effects of a cross with a distinct sub-variety on the
height, but not on the fertility, of the offspring.--Cyclamen persicum,
crossed seedlings greatly superior to the self-fertilised.--Anagallis
collina.--Primula veris.--Equal-styled variety of Primula veris, fertility
of, greatly increased by a cross with a fresh stock.--Fagopyrum
esculentum.--Beta vulgaris.--Canna warscewiczi, crossed and
self-fertilised plants of equal height.--Zea mays.--Phalaris canariensis.

CHAPTER VII.
SUMMARY OF THE HEIGHTS AND WEIGHTS OF THE
CROSSED AND SELF-FERTILISED PLANTS.
Number of species and plants measured.--Tables given.--Preliminary

remarks on the offspring of plants crossed by a fresh stock.--Thirteen
cases specially considered.--The effects of crossing a self-fertilised
plant either by another self-fertilised plant or by an intercrossed plant of
the old stock.--Summary of the results.--Preliminary remarks on the
crossed and self-fertilised plants of the same stock.--The twenty-six
exceptional cases considered, in which the crossed plants did not
exceed greatly in height the self-fertilised.--Most of these cases shown
not to be real exceptions to the rule that cross-fertilisation is
beneficial.--Summary of results.--Relative weights of the crossed and
self-fertilised plants.

CHAPTER VIII.
DIFFERENCE BETWEEN CROSSED AND SELF-FERTILISED
PLANTS IN CONSTITUTIONAL VIGOUR AND IN OTHER
RESPECTS.
Greater constitutional vigour of crossed plants.--The effects of great
crowding.--Competition with other kinds of plants.--Self-fertilised
plants more liable to premature death.--Crossed plants generally flower
before the self-fertilised.--Negative effects of intercrossing flowers on
the same plant.--Cases described.--Transmission of the good effects of
a cross to later generations.--Effects of crossing plants of closely
related parentage.--Uniform colour of the flowers on plants
self-fertilised during several generations and cultivated under similar
conditions.

CHAPTER IX.
THE EFFECTS OF CROSS-FERTILISATION AND
SELF-FERTILISATION ON THE PRODUCTION OF SEEDS.
Fertility of plants of crossed and self-fertilised parentage, both lots
being fertilised in the same manner.--Fertility of the parent-plants when

first crossed and self-fertilised, and of their crossed and self-fertilised
offspring when again