Page:Popular Science Monthly Volume 9.djvu/427

Rh is one of the few moulds which grow on oil or oily substances, and is so filthy in its habits as to flourish in the sewers and cesspools of cities. It is so much like Fig. 2 in structure and manner of fruiting, though many times larger, that it must pass without an illustration.

The pulp of oranges is an especially favorable diet for some of the most delicate moulds. A culture made of it will show decided signs of mouldiness in twenty-four hours, and after thirty-six hours of growth there is a fine crop for study. Those which we have seen on the bread are invariably the first to appear here, though followed in a short time by others, one of the most common of which is given in Fig. 5. At the base a are some mycelial threads which penetrate the tissue of the pulp, and from them, as they come to the surface, arise the fruit-stalks which branch near the top into a loose head with the spore capsules borne on the ends of the branches. At c is one of the Sporangia more highly magnified, showing the spores to be larger and few in number as compared with the Mucor. This species is a member of the same family with those already mentioned, and has its similar zygaspores.



Corn-starch pudding, when placed in a bell-jar, remained unchanged until the fourth week, when its surface became coated with a peculiar yellow-colored substance, and a day or so after black specks began to appear. When viewed with the microscope, this mould exhibited the structure seen in Fig. 6. There arises from the unbranched and imbedded filaments a very much swollen end (a and b) filled with protoplasm, yellow globules of oil, and crystals (d). As this end increases in size, a contraction takes place near the upper end, and soon a distinct spore capsule is formed of the end thus separated. When the plant is ripe a black elastic coat covers the spore-case, which slips partly off when the spores are discharged from below. There are several