112 REPRODUCTION. [CH. VIII 



convenient. Mucor like other fungi is devoid of chloro- 

 phyll, it does not earn its own living, but depends, like 

 yeast, on the material previously built up by some other 

 organism. Ripe fruit, jam, bread and other similar things, 

 when left to themselves and kept warm and damp, become 

 covered with a crop of some kind of mould. Such a result 

 is practically universal, because the reproductive cells or 

 spores of the mould, being small and light, float in the 

 air and are universally distributed; they settle like dust 

 on everything, and thus chance on the organic materials 

 which can support them. The spore germinates, that is, 

 it begins to grow and to take on the form of a delicate tube 

 known as a hypha. The hypha grows, branching as it 

 elongates, and covers the substratum with a delicate 

 colourless web or fluff made up of countless interwoven 

 tubes, sending other branches like roots into the sub- 

 stance on which it lives. This irregular web of branching 

 tubes constitutes the whole of the absorptive part of the 

 plant and is collectively described by the term mycelium. 

 The most remarkable point in its structure is that it is not 

 made up of a regular series of cells; it has occasional 

 cross-walls, but it is not divided into the numerous small 

 compartments or cells seen in the plants previously 

 studied. There is little to be seen in the hypha except 

 oily protoplasm containing vacuoles: by the use of 

 staining reagents numerous small nuclei can be seen. 



After a time other structures make their appearance : 

 minute rods grow vertically up in the air, each crowned 

 with a little ball, and looking like small round-headed 

 pins. These are called spore-bearing hyphce, and the pin 



