MUCOR. . 199 



brown, or black globules may be distinguished by the naked 

 eye. Only the more commonly occurring species are described.* 



Mucor Mucedo (Fig. 35), one of the most beautiful mould 

 growths, and one which occurs very generally on the excreta 

 of herbivorous animals and especially on horse excreta, has 

 a transparent white mycelium, which develops numerous 

 and delicate ramifications both above and below the surface 

 of the substratum. In its earliest stages of development, and 

 until the sporangia begin to form, it is without transverse 

 septa, and, therefore, unicellular. Single vigorous branches, 

 the sporangiophores, rise from the mycelium ; the points of 

 these branches which, according to Zopf, contain a reddish- 

 yellow fatty colouring matter, swell greatly, the protoplasm 

 withdraws from the stalk into the enlarged heads, and below 

 the swelling a transverse septum is finally formed whereby 

 the sporangium is cut off from the sporangiophore. The 

 transverse wall arches upwards, and forms a short column 

 (columella) in the interior of the spherical head, whereby an 

 inner space of peculiar form (1) results. The protoplasm of 

 this space breaks up into a number of small portions, which 

 are gradually surrounded by a membrane and rounded off ; 

 these are the spores. At the same time the sporangium is 

 coated on its outer surface with small needle-shaped crystals 

 of calcium oxalate. As soon as the ripe greyish-brown spor- 

 angium takes up moisture, the wall dissolves, and the spores 

 with their yellowish contents are scattered on all sides along 

 with the swelling contents of the sporangium. The columella, 

 which projected upwards in the sporangium, still remains at 

 the end of the sporangiophore ; this is now surrounded at 

 its base by a collar (2), the remains of the outer wall of the 

 sporangium. When the refractive spores fall on a favourable 

 substratum, they swell very considerably, and send out one 

 or two germ tubes (3, 4), which quickly develop to a vigorous 

 mycelium. The optimum for growth lies between 20 and 25 C. 



In addition to this mode of reproduction, Mucor Mucedo 

 and the other species possess a sexual method of reproduction, 

 wnich takes place by means of a conjugation of two branches 

 of the same mycelium. Two such short branches, filled with 



* A systematic description has been given by Fischer and von Schroeter. 



