Note 4 — PHYSIOGNOMY OF PLANTS.

p. 5.—“Winged insects.”

Formerly the fertilization of flowers in which the sexes are separated was ascribed principally to the action of the wind: it has been shown by Kölreuter, and with great ingenuity by Sprengel, that bees, wasps, and a host of smaller winged insects, are the chief agents. I say the chief agents, because to assert that no fertilization is possible without the intervention of these little animals appears to me not to be in conformity with nature, as indeed has been shown in detail by Willdenow. (Grundriss der Kräuterkunde, 4te Aufl., Berl. 1805, S. 405-412.) On the other hand, Dichogamy, coloured spots or marks indicating honey-vessels (maculæ indicantes), and fertilization by insects, are, in much the greater number of cases, inseparably associated. (Compare Auguste de St. Hilaire, Leçons de Botanique, 1840, p. 565-571.)

The statement which has been often repeated since Spallanzani, that the diœcious common hemp (Cannabis sativa) yields perfect seeds without the neighbourhood of pollen-bearing vessels, has been refuted by later experiments. When seeds have been obtained, anthers in a rudimentary state, capable of furnishing some grains of fertilizing dust, have been discovered near the ovarium. Such hermaphroditism is frequent in the entire family of Urticeæ, but a peculiar and still unexplained phenomenon has been presented in the forcing-houses at Kew by a small New Holland shrub, the Cœlebogyne of Smith. This phænogamous plant produces in England perfect seeds without trace of male organs, or the hybridising introduction of the pollen of other species. An ingenious botanist, Adrien de Jussieu, in his “Cours Elementaire de Botanique,” 1840, p. 463, expresses himself on the subject as follows:—“Un genre d’Euphorbiacées (?) assez nouvellement décrit mais cultivé depuis plusieurs années dans les serres d’Angleterre, le Cœlebogyne, y a plusieurs fois fructifié, et ses graines étaient évidemment parfaites, puisque non seulement on y a observé un embryon bien constitué, mais qu’en le semant cet embryon s’est développé en une plante semblable. Or les fleurs sont dioïques; on ne connait et ne possède pas (en Angleterre) de pieds mâles, et les recherches les plus minutieuses, faites par les meilleurs observateurs, n’ont pu jusqu’ici faire découvrir la moindre trace d’anthères ou seulement de pollen. L’embryon ne venait donc pas de ce pollen, qui manque entièrement: il a dû se former de toute pièce dans l’ovule.”

In order to obtain a fresh confirmation or elucidation of this highly important and isolated phenomenon, I addressed myself not long since to my young friend Dr. Joseph Hooker, who, after making the Antarctic voyage with Sir James Ross, has now joined the great Thibeto-Himalayan expedition. Dr. Hooker wrote to me in reply, on his arrival at Alexandria near the end of December 1847, before embarking at Suez: “Our Cœlebogyne still flowers with my father at Kew as well as in the Gardens of the Horticultural Society. It ripens its seeds regularly: I have examined it repeatedly very closely and carefully, and have never been able to discover a penetration of pollen-tubes either in the style or ovarium. In my herbarium the male blossoms are in small catkins.”