v.] . MOULDS. 35 



enlarge, become spheroidal, and then send out several 

 thick prolongations. Each of these elongates, by constant 

 growth at its free end, and becomes a hypha, from which 

 branches are given off, which grow and ramify in the same 

 way. As all the ramifying hyphse proceed from the spore 

 as a centre, their development gives rise, as in Penicillium, 

 to a delicate stellate mycelium. At first, no septa are deve- 

 loped in the hyphse, so that the whole mycelium may be 

 regarded as a single cell with long and ramified processes, 

 and the Mucor, at this stage, is an unicellular organism. 

 From near the centre of the mycelium a branch is given off 

 from a hypha, rises vertically, and after attaining a certain 

 length ceases to elongate. Its free end dilates into a 

 rounded head, which gradually increases in size, until it 

 attains the dimensions of a full-grown sporangium; and, at 

 the same time, the protoplasm contained in this head 

 becomes separated from that in the stalk by a septum, 

 which is curved towards the cavity of the sporangium, and 

 constitutes the columella. The wall of the sporangium, 

 thus formed, becomes covered externally with a coat of 

 oxalate of lime spines. As the sporangium increases in 

 size, its protoplasmic contents become marked out into a 

 large number of small oval masses, which are close together, 

 but not in actual contact. Each of these masses next 

 becomes completely separate from the rest, surrounds itself 

 with a cellulose coat, and becomes a spore; while the 

 protoplasm not thus used up in the formation of spores, 

 appears to give rise to the gelatinous intermediate sub- 

 stance, which swells up in water, referred to above. The 

 walls of the spores become coloured, and that of the spo- 

 rangium gradually thins, until it is reduced to little more' 

 than the outer crust of oxalate of lime. The sporangium 

 now readily bursts, and the spores are separated by the 



9 2 



