i6o MUCOR LESS. 



F, spores. 



G', g^, g', three stages in the germination of the spores. 

 H, a group of germinating spores forming a small mycelium, 

 i' — I**, five stages in conjugation, showing two gametes {gam) uniting 

 to form the zygote {zyg). 



k', k^ development of ferment cells from submerged hyphae. 

 (A, C^, D, E, F, G, and K, after Howes ; I, after De Bary.) 



ascertained to be connected with others {my) which form a 

 network ramifying through the substance of the bread or 

 horse-dung. This network is called a mycelium ; the threads 

 of which it is composed are mycelial hyphce ; and the fila- 

 ments which grow out into the air and give the characteristic 

 fluffy ajipearance to the growth are aerial hyphce. 



The aerial hyphse are somewhat thicker than those which 

 form the mycelium, and are at first of even diameter through- 

 out : they continue to grow until they attain a length, in M. 

 mucedo, of 6-8 cm. (two or three inches). As they grow 

 their ends are seen to become dilated, so that each is termi- 

 nated by a minute knob (a, spg) : this increases in size and 

 darkens in tint until it finally becomes dead black. In its 

 earlier stages the knobs may be touched gently without 

 injury, but when they have attained their full size the 

 slightest touch causes them to burst and apparently to dis- 

 appear — their actual fate being quite invisible to the naked 

 eye. As we shall see, the black knobs contain spores, and 

 are therefore called sporangia or spore-cases. 



Examined under the microscope, a hypha is found to be 

 a delicate, more or less branched, tube, with a clear trans- 

 parent wall (b, c. w) and slightly granular contents (plsm) : 

 its free end tapers slightly (h), and the wall is somewhat 

 thinner at the extremity than elsewhere. If a single hypha 

 could be obtained whole and unbroken, its opposite end 

 would be found to have much the same structure, and each 

 of its branches would also be seen to end in the same way. 



