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Dissemination by ants of the seeds of Trillium grandiflorum

1940; New England Botanical Club; Volume: 42; Linguagem: Inglês

1938-3401

Burton N. Gates,

Potato Plant Research

The fruit of Trillium is three-celled, subglobose, varying around one-half inch in long diameter and contains numerous seeds. When ripe, separating at the calyx, the fruit falls to the ground without opening, but seeds are exposed at the base of the capsule where it is detached. The seeds are relatively large, easily seen, and change in color, on exposure to the air, from a whitish or light brown to a darker, reddish brown. On removal from the fruit, the ovate seeds appear to be coated with a viscous or gelatinous substance, which will dry. Moisture apparently revives this viscosity. (The viscous or gelatin ous quality suggests that there may be an adaptation for seed-dis persal by means of adhesion to animals.) At the hilum is a spongy caruncle, roughly one-fourth the bulk of the seed. Similar fleshy material forms the axis of the fruit. The capsule when quite empty is thin and papery. Apparently, the plant has no mechanical means of scattering its seeds. For experimentation on the germination of seeds of T. grandiflorum Salisb. we had received a request for all of the fresh seeds which could be procured from our plants. The first fruits ripened, falling readily into the hand, on July 13, 1939 (Worcester, Mass.), four fruits being collected that evening. The next morning a number of fruits had ripened and had fallen to the ground. Surprisingly, on examination not one of these had a seed remaining in it; after a prolonged search, not a seed could be found on the ground. Examination of empty capsules revealed that they had been thoroughly cleaned out, leaving only the thin, papery shell. It was far from apparent how these viscous seeds could have completely disappeared from the capsules and the ground in such a short time. There had been no rain. The next day more ripened fruits were collected; more emptied capsules were seen beneath the plants, all quite devoid of seeds. It was re called then, that on the previous day, two empty capsules each con tained a black ant. Instantly, a relationship between ants and the disappearance of the seeds was suspected. A test was made. A freshly harvested fruit was offered to a black ant (species undetermined) crawling on the ground. With apparent familiarity, she at once mounted the fruit, at the freshly-exposed end. Within a few seconds she dug out a seed, adjusted it in her mandibles,