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 hyphae 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 



32 



