Page:Popular Science Monthly Volume 39.djvu/84

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74
THE POPULAR SCIENCE MONTHLY.

and, when I held a magnifying glass over them, it was like looking down on a fairy forest of brown-stemmed, branching trees covered with a luxuriant, silvery foliage. In this miniature tree I recognized a mold called Polyactis (many-branched), a fungus that is sure to show itself, sooner or later, on decaying vegetables. To remove one of the little trees and place it under the microscope required as much patient care as I could muster; for not only does the Polyactis take a firm hold of the leaf-base with its spreading, root-like hyphæ, but at the least jar it sheds its foliage, branches and all, and nothing remains but an uninteresting, pointed stem. Yet, if we could continuously watch this stem for a day

PSM V39 D084 Polyactis cinerea.jpg
Fig. 2. — Polyactis cinerea.

or so, it would prove anything but uninteresting. Almost at once the protoplasm stored within it begins to form other branches as luxuriant as those that fell. When each is furnished with a due amount, a partition cuts it off from the main supply. Henceforth it rests merely upon the parent stem. It sends out branches on its own account, and gradually gives over its protoplasm to them. These branches fork and fork again, until at last the protoplasm is all concentrated in the ends of tiny branchlets, which swell and sprout all over with little points or sterigmata. Each little point contracts and then swells at the end to form an oval, bladder-like body. It is these oval bodies that give the look of foliage to the Polyactis, and as soon as they have received the whole nourishment of the branchlets they cut themselves off from their sterigmata and hang together in a grape-like cluster. These are the conidia that it has been the business of the whole plant to produce, and, in order that more may be borne by the same stem, they must speedily fall and carry the empty branches with them.

The third crop appeared where I least expected to see it — on the heads of my Polyactis. First of all, fine, silvery lines ran from one Polyactis tree to another, looking, through the magnifying glass, like part of some complicated system of telegraph wires. In a day or two they formed a perfect network, on which pink dots began to appear. The dots increased in number, and soon the Polyactis was completely covered with a pinkish film. The