FUNGI. 55 



bell jar or tumbler in a warm room, in the course of twenty- 

 four hours or so it will be covered with a film of fine white 

 threads, and a little later will produce a crop of little globular 

 bodies mounted on upright stalks. These are at first white, 

 but soon become black, and the filaments bearing them also 

 grow dark-colored. 



These are moulds, and have grown from spores that are in 

 the atmosphere falling on the bread, which offers the proper 

 conditions for their growth and multiplication. 



One of the commonest moulds is the one here figured (Fig. 

 32), and named Mucor stolonifer, from the runners, or "stolons," 

 by which it spreads from one point to another. As it grows 

 it sends out these runners along the surface of the bread, or 

 even along the inner surface of the glass covering it. They 

 fasten themselves at intervals to the substratum, and send up 

 from these points clusters of short filaments, each one tipped 

 with a spore case, or " sporangium." 



For microscopical study they are best mounted in dilute glycerine 

 (about one-quarter glycerine to three-quarters pure water). After care- 

 fully spreading out the specimens in this mixture, allow a drop of alcohol 

 to fall upon the preparation, and then put on the cover glass. The alcohol 

 drives out the air, which otherwise interferes badly with the examina- 

 tion. 



The whole plant consists of a very long, much-branched, but undivided 

 tubular filament. Where it is in contact with the substratum, root-like 

 outgrowths are formed, not unlike those observed in Vaucheria. At first 

 the walls are colorless, but later become dark smoky brown in color. 

 A layer of colorless granular protoplasm lines the wall, becoming more 

 abundant toward the growing tips of the branches. The spore cases, 

 "sporangia," arise at the ends of upright branches (Fig. 32, O), which at 

 first are cylindrical (a), but later enlarge at the end (6), and become cut 

 off by a convex wall (c). This wall pushes up into the young sporangium, 

 forming a structure called the "columella." When fully grown, the 

 sporangium is globular, and appears quite opaque, owing to the numerous 

 granules in the protoplasm filling the space between the columella and 

 its outer wall. This protoplasm now divides into a great number of small 

 oval cells (spores), which rapidly darken, owing to a thick, black wall 



