Kesselfallenprinzip bei der Bestäubung des Aronstabs. Anthese und Welken der Infloreszenz; Schmetterlingsmücken (Psychoda spec.) als Bestäuber. Protogynie. Normalfrequenz und Zeitraffung.

In the film the interesting example of a trap plant, catching insects for pollination, as to be found in Arum maculatum L., the Fly Trap, is demonstrated. After introduction by outdoor pictures of a population of this species, just being in the flowering period, the whole of course of the anthesis of this monoecious and protoynous inflorescence is shown. Impressive close-up pictures of the fertile part of the inflorescence situated in the chamber, formed by the lower part of the spathe, follow. This part is constructed by revolving of the spathe, a large hypsophyll at the base of the inflorescence, and by tieing up form the upper part of the spathe, which unrolls before the anthesis starts. This chamber functions as a trap for small insects, which landing on the upper smooth part of the spathe hurl down into the trag. The chamber contains the spadix of the inflorescence, covered at the base with female flowers consisting of naked ovaries with hairy stigmas and above them with male floswers of only 3-4 stamens. Just beneath the corded part of the spathe some sterile female flowers act as bristles like a weir-basket. On the top of the spadix a smooth purplish appendix juts out of the chamber, standing before the unrolled upper part of the spathe and emanating an urine-like scent. the female flowers at first ripe in the afternoon and exudeduring the night small droplets of nectar by the stigma. if insects are missing, these droplets are resorbed, while otherwise trapped insectsmtake them up. During the following male period of the inflorscence, which starts on the next morning and runs quickly, the antheres open and discharge the pollen grains. These trinkle down to the insects, small midges of the genus Psychoda, enabling them to pollinate female flowers of an other inflorescenece, if they leave the trap after wilting of the bristles of the weirbasket about 24 hours later and hurling down to the chamber of the next plant being in anthesis. The film ends eith outdoor pictures of the infructescences of Arum maculatum in the autumn with red berries.