3i ELEMENTARY BIOLOGY. [V. 



stellate mycelmm. At first, no septa are developed in the 

 hyphse, so that the whole mycelium may be regarded as 

 a single cell with long and ramified processes, and the 

 Miicor, 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 proto- 

 plasm 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- 

 iacreases 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 celkdar coat, and becomes a spore ; while the pro- 

 toplasm not thus used up in the formation of spores, appears 

 to give rise to the gelatinous intermediate substance, which 

 swells up in water, referred to above. The walls of the spores 

 become coloured, and that of the sporangium gradually thins, 

 imtil 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 swelling and eventual dissolution 

 of the gelatinous intermediate matter. Sporangia, in which 

 spores are produced by division of the protoplasm, are com- 

 monly termed asci, and the spores receive the name of asco- 

 spores. 



There appears to be no limit to the extent to which the 

 Mucar may be reproduced by this process of asexual develop- 

 ment of spores, by the fission of the contents of the sporang- 

 ium; nor does any other mode of multiplication become 



