=388. Asexual reproduction.=—On the decaying surface of the vegetable matter where the mucor is growing there will be seen numerous small rounded bodies borne on very slender stalks. These heads contain the gonidia, and if we sow some of them in nutrient gelatine or agar in a Petrie dish the material can be taken out very readily for examination under the microscope. Or we may place glass slips close to the growing fungus in the moist chamber, so that the fungus will develop on them, though cultures in a nutrient medium are much better. Or we may take the material directly from the substance on which it is growing. After mounting a small quantity of the mycelium bearing these heads, if we have been careful to take it where the heads appear quite young, it may be possible to study the early stages of their development. We shall probably note at once that the stalks or upright threads which support the heads are stouter than the threads of the mycelium. [Illustration: Fig. 190. Portion of banana with a mould (Rhizopus nigricans) growing on one end.] These upright threads soon have formed near the end a cross wall which separates the protoplasm in the end from the remainder. This end cell now enlarges into a vesicle of considerable size, the head as it appears, but to which is applied the name of _sporangium_ (sometimes called gonidangium), because it encloses the _gonidia_. At the same time that this end cell is enlarging the cross wall is arching up into the interior. This forms the _columella_. All the protoplasm in the sporangium now divides into gonidia. These are small-rounded or oval bodies. The wall of the sporangium becomes dissolved, except a small collar around the stalk which remains attached below the columella (fig. 192). By this means the gonidia are freed. These gonidia germinate and produce the mycelium again. [Illustration: Fig. 191. Group of sporangia of a mucor (Rhizopus nigricans) showing rhizoids and the stolon extending from an older group.] =389. Sexual stage.=—This stage is not so frequently found, but may sometimes be obtained by growing the fungus on bread.