Chapter 10 - Page 2

[LIST OF PLANTS WHICH, WHEN INSECTS ARE EXCLUDED, ARE EITHER QUITE STERILE, OR PRODUCE, AS FAR AS I COULD JUDGE, LESS THAN HALF THE NUMBER OF SEEDS PRODUCED BY UNPROTECTED PLANTS.

Passiflora alata, racemosa, coerulea, edulis, laurifolia, and some individuals of P. quadrangularis (Passifloraceae), are quite sterile under these conditions: see 'Variation of Animals and Plants under Domestication' chapter 17 2nd edition volume 2 page 118.

Viola canina (Violaceae).--Perfect flowers quite sterile unless fertilised by bees, or artificially fertilised.

Viola tricolor.--Sets very few and poor capsules.

Reseda odorata (Resedaceae).--Some individuals quite sterile.

Reseda lutea.--Some individuals produce very few and poor capsules.

Abutilon darwinii (Malvaceae).--Quite sterile in Brazil: see previous discussion on self-sterile plants.

Nymphaea (Nymphaeaceae).--Professor Caspary informs me that some of the species are quite sterile if insects are excluded.

Euryale amazonica (Nymphaeaceae).--Mr. J. Smith, of Kew, informs me that capsules from flowers left to themselves, and probably not visited by insects, contained from eight to fifteen seeds; those from flowers artificially fertilised with pollen from other flowers on the same plant contained from fifteen to thirty seeds; and that two flowers fertilised with pollen brought from another plant at Chatsworth contained respectively sixty and seventy-five seeds. I have given these statements because Professor Caspary advances this plant as a case opposed to the doctrine of the necessity or advantage of cross-fertilisation: see Sitzungsberichte der Phys.-okon. Gesell.zu Konigsberg, B.6 page 20.)

Delphinium consolida (Ranunculaceae).--Produces many capsules, but these contain only about half the number of seeds compared with capsules from flowers naturally fertilised by bees.

Eschscholtzia californica (Papaveraceae).--Brazilian plants quite sterile: English plants produce a few capsules.

Papaver vagum (Papaveraceae).--In the early part of the summer produced very few capsules, and these contained very few seeds.

Papaver alpinum.--H. Hoffmann ('Speciesfrage' 1875 page 47) states that this species produced seeds capable of germination only on one occasion.

Corydalis cava (Fumariaceae).--Sterile: see the previous discussion on self-sterile plants.

Corydalis solida.--I had a single plant in my garden (1863), and saw many hive-bees sucking the flowers, but not a single seed was produced. I was much surprised at this fact, as Professor Hildebrand's discovery that C. cava is sterile with its own pollen had not then been made. He likewise concludes from the few experiments which he made on the present species that it is self-sterile. The two foregoing cases are interesting, because botanists formerly thought (see, for instance, Lecoq, 'De la Fecondation et de