MTJCOR. 291 



mycelium, treat preparations of fresh Mucor with (1) salt 

 solution, which will cause plasmolysis and make the pro- 

 toplasmic lining visible ; (2) iodine, which stains the 

 protoplasm brown note that the hyphae contain no 

 starch. 



(e) The numerous small nuclei in the hyphae can be 

 demonstrated on staining, with haematoxylin, material 

 that has been fixed with alcohol or picric acid or chromo- 

 acetic acid (1 gram chromic acid and 2 c.c. glacial acetic 

 to 200 c.c. water). 



420. Structure and Development of Gonidangium. 



Examine gonidiophores before their tips have begun to 

 turn black. Note that (1) the end of the gonidiophore 

 becomes swollen up and pear-shaped ; (2) a cross- wall is 

 formed below the swelling, cutting off the gonidangium ; 



(3) the latter now enlarges and becomes spherical; 



(4) the cross-wall bulges upwards into the cavity of the 

 gonidangium, forming the columella. 



Carefully seize with forceps a number of mature goni- 

 diophores, a little below the gonidangia themselves, cut 

 them off with scissors, and mount in alcohol. Note, in 

 an undamaged gonidangium, (1) the thin wall, often 

 covered externally by an incrustation of minute radiating 

 needle-like calcium oxalate crystals not always present ; 

 (2) the dense contents, consisting of the gonidia ; (3) the 

 clear place at the base of the gonidangium, corresponding 

 to the position of the columella. 



421. Dehiscence of Gonidangium. While watching 

 a gonidangium mounted in alcohol, place a drop of water 

 at one side of the cover-glass, and draw it through with 

 filter- or blotting-paper. Note the sudden dehiscence of 

 the gonidangium, the outer wall being broken into frag- 

 ments and the ovoid gonidia escaping along with mucilage. 

 Note also that the columella is left as an ovoid or nearly 

 spherical swelling of the top of the gonidiophore, often 

 surrounded at its base by a fringe representing the lowest 

 portion of the gonidangium wall. 



