Sterki, V.

The Ohio Journal of Science

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June, 1910.] Winter-Buds of Spirodela. 181WINTER-BUDS OF SPIRODELA POLYRHIZA (L.).V. STERKI.Last summer and fall, I brought home several kinds of"duckweeds," and kept them in aquaria, some of the latter beingsmall tumblers. During September and October it was noticedthat there were numerous small disks, or links, partly free, partlyconnected with Spirodela plants. They were flat, short-ellipticalor oblong, or nearly circular, of about one to two mm. diameter,of a deep green color (darker than the spirodela disks), alwaysrootless, without any visible venation and with a small, sharplydefined, crescent-shaped, whitish to brownish hilum at the margin.Microscopic examination, made in February, showed them tohave stomata on the upper surface and a slight but distinctpurplish hue on the lower, inside of the epidermis.With the approach of winter, the Spirodela plants fadedand died, but these small bodies kept fresh and green, and mostof them sank to the bottom. Some, however, were kept floatingby the dead disks, now little more than skeletons. Some wereseen as late as February, each being held between the two epi-dermal layers of its parent disk, near the hilum, partly emergingfrom the margin. Several score were in a small tumbler aqua-rium, near a window but not reached by direct sunlight until theend of winter. During the latter part of January, and up tothe present it was noticed that each had a small gas bubble onits upper surface, probably oxygen, and some were raised to thesurface by the same and kept floating. Many of them are nowsprouting, at the hilum, while others are still at the bottom,unchanged. Another such small aquarium, with Lemna tri-182 The Ohio Naturalist. [Vol. X, No. 8,sulea, etc., was kept close to the window, where the sun hadaccess for an hour or two on clear mornings. In that, the plantsdeveloped earlier, and at the present - writing, several of themare fully developed, unmistakable Spirodela polyrhiza, withtwo disks several times the size of the bud, bright green, withdistinct nervation, several roots and with the inferior sidearound the hilum purplish. On one of them, the bud is nowfading and withering.Thus the cycle is complete. The small bodies described wereseen developing on the Spirodela plants, in late summer and fall,then detached or held only mechanically, surviving the winterat the bottom, rising to the surface in spring (premature indoors),producing new plants, and then dying. The observations arecomplete so far as they go; but more details and further investi-gations will be in place. It has not been ascertained whetherone Spirodela disk produces only one bud or several, how early inthe season they are produced and eventually whether some ofthem grow out into new plants in the same season; also the micro-scopic structure especially of the hilum when dormant and at thetime of sprouting will be of interest. The buds should also betaken up from the bottom of ponds and pools in early springand their development observed..When the little bodies were first noticed, last fall, it was sup-posed that they might be "winter-buds," having the function ofbuds or bulbs, and the result sustained the diagnosis. Since theplant is rarely found blossoming and fruiting these buds are evi-dently the means of propagation of the species. But the term" b u d " is not adequate. They may be compared with the bulb-lets of some Pteridophyta. Their significance is possibly nearestto that of tubers, like those of the Dahlia and potato, but the factthat they are provided with chlorophyl and stomata again setsthem apart. Their configuration is in accordance with thesimple structure of the plant itself.It may be mentioned that a Lemna (trinervis Austin ?) broughtin and kept with the Spirodela showed nothing of the kind des-cribed; but it may have been overlooked; most of them diedearlier than the Spirodela. Lemna trisulca L. keeps well andgrows luxuriantly over winter, indoors, and is a very satisfactoryplant for small aquaria._ New Philadelphia, Ohio, March 12, 1910.

Winter-Buds of Spirodela Polyrhiza (L.)

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Winter-Buds of Spirodela Polyrhiza (L.)

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