A Metaxenia-like Phenomenon found in some Plants of Solanaceae. (Preliminary Report.)

Abstract

Xenia which occurs in the endosperm is commonly found in maize, rice and other plants. But metaxenia is a curious phenomenon. This is caused by the direct action of pollen on the character of the fruit which consists of the ovarial tissues of the mother plant. SWINGLE and NIXON discovered this phenomenon in fruits of the date-plam and the former named it“metaxenia”.
We have observed a sort of metaxenia of Swingle or some such phenomenon in some plants of solanaceae.
The materials used in this experiment were the following three kinds of plants of genus Solanum.
S. citrullifouliun: The fruit is 7.8mm. in diameter on the average. It contains about 42 seeds, and turns red, becoming transparent when it matures
S. Delilei: The diameter of the fruit measures 6.7mm. on the average. Single fruit containing about 43 seeds becomes intransparently black-purple when mature.
S. aggregatum: The fruit is 14mm. in diameter on the average. It containes about 56 seeds, and becomes intransparently deep purple when it matures.
When the pistils of S. citrullifolium were pollinated with the pollen grains of S. Delilei, the fruits grew larger than those of the parents, containing no or very few filled seeds but many unfilled ones, and became, when matured, dark red colour, which was almost intermediate between that of their parents.
When the pistils of S. citrullifolium were pollinated with the pollen grains of S. aggregatum, the fruits became smaller than those of the parents and contained many uufilled seeds but no filled ones. The colour they assumed when ripe was intermediate of the fruits of their parents.
Xenia in the endosperm is easily explained by the double fertilization. But the explanation of metaxenia is still sought for. Swingle says that the embryo or endosperm or both of them secrete hormones, or some such substances, which biffuse out into the tissues of the ovary and affect them according to the particular male parent used to fecundate the embryo and endosperm. This is an interesting and clever explanation. In fact, the fruits grown by cross pollinating in our experiments were bluish in the center or near the seeds. As these fruits are observed through the red juice of the outer side, their colour seems intermediate one. Therefore it seems as though the seeds secrete some substances which change the colour of the fruit. But it must be added here that in all our cases the seeds in the fruits were nearly always unfilled or abortive ones. This fact makes the explanation difficult.
PH value of the juice of all kinds of these fruits were measured, but the results did not bring our cases to light.
Thus we shall reserve the discussion on this problem to still later work.