THE FUNGI 



159 



we may select the very common Mucor stolonifer (RJiizopus nigricans), 

 belonging to the family Mucoracese (Figs. 123, 124). This common 

 Mould forms a dense fleecy white mycelium upon the surface of many 

 articles of food,, and appears spontaneously upon bread exposed to a 

 moist warm atmosphere. The hyphae are thin- walled, colorless at first, 

 but turning dark with age. Slender rootlets are sent down into the 

 nutrient substratum, and from this point, branches of two kinds are 

 produced, upright ones (sporangiophores) and horizontal slender 

 runners, or stolons, which strike root, and produce a new crop of 

 sporangiophores. The protoplasmic contents are quite colorless, 



D 



FIG. 123. Mucor stolonifer. A, sporangiophores connected by stolon, and sending 

 down roots, r, slightly enlarged. B, young sporangiophores, more highly magni- 

 fied. C-E, development of sporangium (X 200). 



densely granular in the growing branches, and often containing con- 

 spicuous granules. Sometimes, as in the Water-moulds, streaming 

 movements are visible. 



Sporangium. Each sporangiophore becomes enlarged at the end, which 

 finally is cut off as a globular sporangium. The partition wall is convex, and 

 grows into the sporangium in the form of a dome, leaving only a narrow space 

 between it and the outer sporangium-wall. The protoplasm within this space 

 becomes divided by deep clefts into a number of parts which divide further until 

 a large number of small bodies (spores) are produced. Each of these becomes 

 surrounded by a thick wall, which assumes a smoky black color, this being also 



