Journal of Heredity, 19(6): 257-268 (June 1928)
Possibly a Hormone Action by the Embryo or Endosperm


The pollen of the date palm. Phoenix dactylifera, and of other species of Phoenix, has been found to exert a direct influence on the size, shape and color of the seed, and also on the size of the fruit, on the speed of development of the fruit and on the time of ripening of the fruit of the vegetatively propagated female varieties of the date palm.

This direct influence of the male parent on the development of the date fruit is precise and definite and varies with the particular male used to fecundate the female flowers. each male exerting approximately the same effect on fruit of all varieties and exerting the same effect in different years. This direct effect of the pollen on the parts of the seed and fruit lying outside the embryo and endospermis called metaxenia.

Metaxenia, unlike xenia, cannot be explained by hereditary elements (chromesomes) brought in by the pollen as no such chromesomes occur in the tissues that show the direct effect of the pollen parent.

The simplest and most probable theory to esplain metaxenia is that the embryo or endosperm or both of them secrete hormones, or soluble substances analogous to them. which diffuse out into the tissues of the mother plant that constitute the seed and fruit and there exert a specific effect on these tissues varying according to the particular male parent used to fecundate the embryo and endosperm.

CybeRose note: Swingle is describing what Focke had originally described as Xenia. By the end of the 19th century, however, the word had come to include the effects of double fertilization; specifically alterations to the endosperm induced by the pollen. East and Hayes (1911) emphatically denied the possibility of Xenia in Focke's sense, and chose to limit the word to effects on the endosperm. Thus, Swingle could either contend against East and Hayes, or coin a new word for Focke's Xenia.