Text-book of botany : morphological and physiological / by Julius Sachs ; translated and annotated by Alfred W. Bennett ; assisted by W.T. Thiselton Dyer.

Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Text-book of botany : morphological and physiological / by Julius Sachs ; translated and annotated by Alfred W. Bennett ; assisted by W.T. Thiselton Dyer. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    834/880 (page 818)
    Verbascum1 and Digitalis, but not Pentstemon, Linaria, or Antirrhinum; among Rosacese, Geum, but not Potentilla. Hybridisation between species belonging to different genera has been observed between Lychnis and Silene, Rhododendron and Azalea, Rhododendron and Rhodora, Azalea and Rhodora, Rhododendron and Kalmia, Rhododendron and Menziesia2, iEgilops and Triticum, and between Echinocactus, Cereus, and Phyl- locactus, to which must be added a few wild forms which appear to be genus- hybrids. Besides the near genetic relationship, the possibility of the production of hybrids depends also on a certain relationship between the parent-plants, which is manifested only in the result of hybridisation, and which Nageli calls ‘ Sexual Affinity.’ This kind of affinity is not always concurrent with the external resemblance of the plants. Thus, for example, hybrids have never been obtained between the apple and pear3, Anagallis arvensis and car idea, Primula officinalis and elalior, or Nigella damascena and saliva, nor between many other pairs of species belonging to the same genus which are very nearly allied to one another; while in other cases very dis- similar forms unite, as jEgilops ovala with Triticum vulgarc, Lychnis diurna with L. Flos-cuculi, Cereus speciosissimus with Phyllocac/us Phyllanthus, the peach with the almond. A still more striking proof of the difference between sexual and genetic affinity is afforded by the fact that varieties of the same species will sometimes be partially or altogether infertile with one another, as e.g. Silene inflata var. alpina with var. angusli/olia, var. latifolia with var. littoralis, &c. When a sexual union is possible between two species A and B, A can usually produce hybrids when fertilised by the pollen of B, and B when fertilised by the pollen of A (reciprocal hybridisation). But there are cases in which A can only be the male and B only the female parent plant, the pollination of A by B yielding no result. Thus Thuret found, as has already been mentioned, that Fucus vesiculosus produces hybrids with the spermatozoids of F. serra/us, while the oospheres of the latter species could not be fertilised by the spermatozoids of the former. Gartner states that Nicotiana paniculala produces seeds when acted on by the pollen of N. Langsdorfii, while the latter does not under the influence of the pollen of the former. Kolreuter easily obtained seeds of Mirabilis Jalappa with the pollen of M. longiflora, while more than two hundred experiments on pollinating the latter by the former species extending over eight years produced no result. Sexual Affinity presents a great variety of gradations. At one extreme we have complete infertility under the influence of the pollen of another variety or species, the pollen-tubes not even entering the stigma, and the pollinated flower behaving pre- cisely as if no pollen had reached it; the other extreme is shown in the production 1 [On hybridity in the genus Verbascum, see Darwin, Journ. Linn. Soc. l868, p. 437.—Ed.] 2 [The history of the plant which is here intended is given in the Botanical Gazette, vol. Ill, p. 82. It was raised from seed of Bryanthus (Menziesia) empetriformis, supposed to be fertilised by the pollen of Rhodothamnus (Rhododendron) Chamcecistus. It is figured under the name of Bryanthus ereclus in Paxton’s Flower Garden, vol. I, t. 19 ; but it agrees well with specimens of its female parent from the Rocky Mountains, and is probably therefore not a hybrid at all.—Ed.] 3 [An instance to the contrary is recorded in the Proc. Acad. Philadelphia, 1871, vol. I, p. 10. —Ed.]