[208]

Lotus Jacobaeus

[figure, data not transcribed]

[208v]

3  614

Chap. E 10

are either quite sterile or produce less than about half the full compliment of seeds, when insects are excluded; the & a second list including of plants which when thus treated are fully sterile fertile or produce at lease half the full compliment of seeds. (a) It should be understood observe that the sterility and fertility of the plants in these two lists depends on two wholly distinct causes, ─ the absence of the proper means by which pollen is applied carried to the stigma, and its greater or less efficiency when thus applied. As it is obvious that with plants, in which having the sexes are separated, pollen must be carried by some means from flower to flower, these are excluded from the lists; as are likewise dimorphic and trimorphic plants in which the same necessity occurs to a certain extent. Experience has proved to me that the fertility of a plant is not lessened by covering it while in flower under a thin net supported on a frame, and this might indeed have been inferred from the consideration of the two following lists, as

[Cross and self fertilisation, pp. 356-7: "I will in the first place give two lists: the first, of plants which are either quite sterile or produce less than about half the full complement of seeds, when insects are excluded; and a second list of plants which, when thus treated, are fully fertile or produce at least half the full complement of seeds. These lists have been compiled from the several previous tables, with some additional cases from my own observations and those of others. The species are arranged nearly in the order followed by Lindley in his 'Vegetable Kingdom.' The reader should observe that the sterility or fertility of the plants in these two lists depends on two wholly distinct causes; namely, the absence or presence of the proper means by which pollen is applied to the stigma, and its less or greater efficiency when thus applied. As it is obvious that with plants in which the sexes are separate, pollen must be carried by some means from flower to flower, such species are excluded from the lists; as are likewise dimorphic and trimorphic plants, in which the same necessity occurs to a limited extent. Experience has proved to me that, independently of the exclusion of insects, the seed-bearing power of a plant is not lessened by covering it while in flower under a thin net supported on a frame; and this might indeed have been inferred from the consideration of the two following lists, as they include a considerable number of species belonging to the same genera, some of which are quite sterile and others quite fertile when protected by a net from the access of insects."]