Page:Popular Science Monthly Volume 39.djvu/85

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75
MY GARDEN ON AN ONION.

film was pretty in itself, and I was forced to admire it, although I regretted the untimely extinction of my Polyactis. Shortly, however, it turned a dingy brown and fell to the onion, crushing the Polyactis under it. The conidia of the Polyactis germinated, and sent up another crop of tiny trees; but they had not run their little cycle of changes long, before the fine white lines appeared among them. The pinkish film followed, and then, again, film and Polyactis fell to the onion in a dirty-looking mass. The Polyactis took a fresh part of the leaf-base; the pink film followed it. Polyactis tried the inner side of the leaf-base; the film found it even there. The Polyactis crept up the sprouts that had burst through the scales; the film still pursued it — in fact, the Polyactis could grow nowhere on this onion without being overrun by the silvery threads.

PSM V39 D085 Polyactis overrun by baryeidamia parasitica.jpg
Fig. 3. — Polyactis overrun by Baryeidamia parasitica.

For days I watched the strife with naked eye, magnifying glass, and microscope, and saw the Polyactis gradually succumb and the onion itself rot and blacken under the repeated attacks of the pink-dotted film.

The microscope showed the film to be a tangle of fine, transparent hyphæ, and the pink dots little balls containing spores. Very beautiful are these Baryeidamia spore-balls, changing, as they mature, from pink to a rich seal brown, and surrounded always with clear, scalloped edges. In such profusion, also, are they produced that hundreds of them may be taken up at once on the point of a needle.

Though the most successful, these were by no means all the crops that my onion bore; at least three other minute fungi struggled for existence, but could gain no headway against the pink-filmed Baryeidamia. These, like the Penicillium, Polyactis, and Baryeidamia itself, were all of a comparatively harmless kind. They were merely scavengers, seeking their living on parts of the onion already dead, and thriving on material that it no longer had power to use. The onion, however, had nourished at least one fungus of a very different nature. My microscope showed me its clear, crescent-shaped conidia, and in the tissues of the leaf-bases its hyphæ were creeping from cell to cell, stealing