In most of the fungi which concern us we shall find that there is a mass of minute, thread-like structures forming the main body of the fungus and that, here and there, portions grow erect and bear spores. The spores, it is important to remember, serve the same purpose to the fungus as seeds to the flowering plants. They are blown or carried by insects or other agencies to suitable situations for growth, they germinate and form new fungi. They are smaller and lighter than the most minute and dust-like seeds, so that the slightest breeze scatters them far and wide. Let us compare the white mould with a mushroom; at first sight the two plants appear very dissimilar, in reality they are very similar to one another. The mould forms a thick felt of its threads over the substance on which it grows and mushroom spawn if carefully examined under a microscope will be found to consist of very similar threads, sealed together to form thicker root-like structures. The fungi, however, have no roots and these threads are strictly comparable with those of the mould. Here and there the mould sends a single thread into the air and each of these threads is terminated by a little ball which bursts eventually and sets free its contained spores. The same thing occurs with the mushroom; we have the upright growth, not of a single thread it is true but of a number, welded together to form a fleshy stalk; at the top there is, not a ball containing spores but an umbrella-shaped structure whose under surface is composed of a number of “gills” on which the spores grow at the ends of little stalks. If a piece of the mushroom stem be torn into its separate components and examined under the microscope, its similarity to the more simple fungus is evident. One of the gills also may be carefully cut away and examined; the spores will be seen at the end of small forked stalks. Having progressed thus far in our study of fungus structure, we may examine a few of those which cause damage in farm and garden. For the most part, the thread-like portion of the fungus grows within the plant attacked and only the spore bearing portions appear on the surface. There is one class of fungus, however, the Mildews in which practically all the structure grows on the surface, only a few small, unbranched suckers penetrate the plant attacked, for the purpose of obtaining nourishment.