Page:Popular Science Monthly Volume 9.djvu/426

402 top assumes a very regular, semicircular outline, as shown in Fig. 4, a, where the filaments are represented by single lines; the whole of the branch b is a more highly-magnified view of a dark tip at the end of one of the branches in a and at c is shown, on a still higher scale, one of the ultimate branches in b, with the spores arranged in rows of four around the enlarged end; while d is one of those tips after the spores have fallen away.

The reader will please bear in mind that this figure, and all the others, with the single exception of the first one, represent the object as greatly enlarged—the microscope used for most of the work magnifying 650 diameters. An entire plant of the one in question (Piptocephalis Fresœniana) is scarcely visible to the naked eye when prepared on a glass slide for investigation with the microscope.



That which makes this mould of particular interest is the fact that it is a parasite, and cannot live unless it has some other mould upon which to grow. This easily explains why it does not make its appearance until the Mucor is well established. Here we have a true parasite growing on a saprophyte; or one mould which steals its substance from another which derives its living from the bread. We will not stop to reason upon the matter, or wonder how this strange state of things came about, but will leave the fact as it exists to those who would know the cause of all things both great and small.

There were two or three other members of the Mucor genus which grew on various cultures, but, as they differ only in minor points of structure from the one treated, space will not permit of their being further mentioned.

The bones of a recently-killed dog proved to be very well adapted for the growth of the largest-known species of mould. Those who have a passion for scientific names may call it Phycomyces nitens. It