The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom Part 57

Petunia violacea (Solanaceae).--Quite sterile, as far as I have observed.

Solanum tuberosum (Solanaceae).--Tinzmann says ('Gardeners' Chronicle'

1846 page 183) that some varieties are quite sterile unless fertilised by pollen from another variety.

Primula scotica (Primulaceae).--A non-dimorphic species, which is fertile with its own pollen, but is extremely sterile if insects are excluded. J. Scott in 'Journal of the Linnean Society Botany' volume 8 1864 page 119.

Cortusa matthioli (Primulaceae).--Protected plants completely sterile; artificially self-fertilised flowers perfectly fertile. J. Scott ibid.

page 84.

Cyclamen persic.u.m (Primulaceae).--During one season several covered-up plants did not produce a single seed.

Borago officinalis (Boraginaceae).--Protected plants produced about half as many seeds as the unprotected.

Salvia tenori (l.a.b.i.atae).--Quite sterile; but two or three flowers on the summits of three of the spikes, which touched the net when the wind blew, produced a few seeds. This sterility was not due to the injurious effects of the net, for I fertilised five flowers with pollen from an adjoining plant, and these all yielded fine seeds. I removed the net, whilst one little branch still bore a few not completely faded flowers, and these were visited by bees and yielded seeds.

Salvia coccinea.--Some covered-up plants produced a good many fruits, but not, I think, half as many as did the uncovered plants; twenty-eight of the fruits spontaneously produced by the protected plant contained on an average only 1.45 seeds, whilst some artificially self-fertilised fruits on the same plant contained more than twice as many, namely 3.3 seeds.

Bignonia (unnamed species) (Bignoniaceae).--Quite sterile: see my account of self-sterile plants.

Digitalis purpurea (Scrophulariaceae).--Extremely sterile, only a few poor capsules being produced.

Linaria vulgaris (Scrophulariaceae).--Extremely sterile.

Antirrhinum majus, red var. (Scrophulariaceae).--Fifty pods gathered from a large plant under a net contained 9.8 grains weight of seeds; but many (unfortunately not counted) of the fifty pods contained no seeds.

Fifty pods on a plant fully exposed to the visits of humble-bees contained 23.1 grains weight of seed, that is, more than twice the weight; but in this case again, several of the fifty pods contained no seeds.

Antirrhinum majus (white var., with a pink mouth to the corolla).--Fifty pods, of which only a very few were empty, on a covered-up plant contained 20 grains weight of seed; so that this variety seems to be much more self-fertile than the previous one. With Dr. W. Ogle ('Popular Science Review' January 1870 page 52) a plant of this species was much more sterile when protected from insects than with me, for it produced only two small capsules. As showing the efficiency of bees, I may add that Mr. Crocker castrated some young flowers and left them uncovered; and these produced as many seeds as the unmutilated flowers.

Antirrhinum majus (peloric var.).--This variety is quite fertile when artificially fertilised with its own pollen, but is utterly sterile when left to itself and uncovered, as humble-bees cannot crawl into the narrow tubular flowers.

Verbasc.u.m phoeniceum (Scrophulariaceae).--Quite sterile. See my account of self-sterile plants.

Verbasc.u.m nigrum.--Quite sterile. See my account of self-sterile plants.

Campanula carpathica (Lobeliaceae).--Quite sterile.

Lobelia ramosa (Lobeliaceae).--Quite sterile.

Lobelia fulgens.--This plant is never visited in my garden by bees, and is quite sterile; but in a nursery-garden at a few miles' distance I saw humble-bees visiting the flowers, and they produced some capsules.

Isotoma (a white-flowered var.) (Lobeliaceae).--Five plants left unprotected in my greenhouse produced twenty-four fine capsules, containing altogether 12.2 grains weight of seed, and thirteen other very poor capsules, which were rejected. Five plants protected from insects, but otherwise exposed to the same conditions as the above plants, produced sixteen fine capsules, and twenty other very poor and rejected ones. The sixteen fine capsules contained seeds by weight in such proportion that twenty-four would have yielded 4.66 grains. So that the unprotected plants produced nearly thrice as many seeds by weight as the protected plants.

Leschenaultia formosa (Goodeniaceae).--Quite sterile. My experiments on this plant, showing the necessity of insect aid, are given in the 'Gardeners' Chronicle' 1871 page 1166.

Senecio cruentus (Compositae).--Quite sterile: see my account of self-sterile plants.

Heterocentron mexicanum (Malastomaceae).--Quite sterile; but this species and the following members of the group produce plenty of seed when artificially self-fertilised.

Rhexia glandulosa (Melastomaceae).--Set spontaneously only two or three capsules.

Centradenia floribunda (Melastomaceae).--During some years produced spontaneously two or three capsules, sometimes none.

Pleroma (unnamed species from Kew) (Melastomaceae).--During some years produced spontaneously two or three capsules, sometimes none.

Monochaetum ensiferum (Melastomaceae).--During some years produced spontaneously two or three capsules, sometimes none.

Hedychium (unnamed species) (Marantaceae).--Almost self-sterile without aid.

Orchideae.--An immense proportion of the species sterile, if insects are excluded.

LIST OF PLANTS, WHICH WHEN PROTECTED FROM INSECTS ARE EITHER QUITE FERTILE, OR YIELD MORE THAN HALF THE NUMBER OF SEEDS PRODUCED BY UNPROTECTED PLANTS.

Pa.s.siflora gracilis (Pa.s.sifloraceae).--Produces many fruits, but these contain fewer seeds than fruits from intercrossed flowers.

Bra.s.sica oleracea (Cruciferae).--Produces many capsules, but these generally not so rich in seed as those on uncovered plants.

Rapha.n.u.s sativus (Cruciferae).--Half of a large branching plant was covered by a net, and was as thickly covered with capsules as the other and unprotected half; but twenty of the capsules on the latter contained on an average 3.5 seeds, whilst twenty of the protected capsules contained only 1.85 seeds, that is, only a little more than half the number. This plant might perhaps have been more properly included in the former list.

Iberis umbellata (Cruciferae).--Highly fertile.

Iberis amara.--Highly fertile.

Reseda odorata and lutea (Resedaceae).--Certain individuals completely self-fertile.

Euryale ferox (Nymphaeaceae).--Professor Caspary informs me that this plant is highly self-fertile when insects are excluded. He remarks in the paper before referred to, that his plants (as well as those of the Victoria regia) produce only one flower at a time; and that as this species is an annual, and was introduced in 1809, it must have been self-fertilised for the last fifty-six generations; but Dr. Hooker a.s.sures me that to his knowledge it has been repeatedly introduced, and that at Kew the same plant both of the Euryale and of the Victoria produce several flowers at the same time.

Nymphaea (Nymphaeaceae).--Some species, as I am informed by Professor Caspary, are quite self-fertile when insects are excluded.

Adonis aestivalis (Ranunculaceae).--Produces, according to Professor H.

Hoffmann ('Speciesfrage' page 11), plenty of seeds when protected from insects.

Ranunculus acris (Ranunculaceae).--Produces plenty of seeds under a net.

Papaver somniferum (Papaveraceae).--Thirty capsules from uncovered plants yielded 15.6 grains weight of seed, and thirty capsules from covered-up plants, growing in the same bed, yielded 16.5 grains weight; so that the latter plants were more productive than the uncovered.

Professor H. Hoffmann ('Speciesfrage' 1875 page 53) also found this species self-fertile when protected from insects.

Papaver vagum.--Produced late in the summer plenty of seeds, which germinated well.

Papaver argemonoides.--According to Hildebrand ('Jahrbuch fur w. Bot.'

B.7 page 466), spontaneously self-fertilised flowers are by no means sterile.

Glaucium luteum (Papaveraceae).--According to Hildebrand ('Jahrbuch fur w. Bot.' B.7 page 466), spontaneously self-fertilised flowers are by no means sterile.

Argemone ochroleuca (Papaveraceae).--According to Hildebrand ('Jahrbuch fur w. Bot.' B.7 page 466), spontaneously self-fertilised flowers are by no means sterile.

Adlumia cirrhosa (Fumariaceae).--Sets an abundance of capsules.

Hypecoum proc.u.mbens (Fumariaceae).--Hildebrand says (idem), with respect to protected flowers, that "eine gute Fruchtbildung eintrete."