PENICILLIUM 471 



favourable conditions the spore germinates, and the buds increase 

 in length and ultimately form hyphse. 



Occasionally a process of conjugation occurs. Two adjacent 

 hyphse send out lateral branches which come in contact with one 

 another, and a septum forms in each, separating a small portion of 

 protoplasm from the rest of the hypha. The apposed walls of the 

 two cells become absorbed and the contents mingle. The mass of 

 protoplasm so formed becomes surrounded with a thick cell-wall, 

 giving rise to an inactive spore-like body, the zygospore, which 

 under favourable conditions develops like an ordinary spore. Some 

 Mucors form thick-walled resting cells, known as chlamydospores, 

 in the vegetative mycelium. 



Certain Mucors form appreciable amounts of alcohol from carbo- 

 hydrates, and M. rouxii has been used for the commercial production 

 of alcohol. 



Penicillium glaucum 



Penicillium belongs to the Ascomycetes, and bears conidiophores. 

 Penicillium glaucum forms the bluish-green mouldy patches familiar 

 to every one. It is by far the commonest of all species, and may 

 be obtained from moist bread or jam or by exposing a gelatin plate 

 to the air for a short time. If the mouldy patch be rubbed a fine 

 greenish dust comes away. This dust consists of myriads of spores ; 

 if a little of it be transferred with a moistened needle to a gelatin 

 plate, or, better still, to a hanging-drop preparation, the growth of 

 the organism can be studied. After two or three days little white 

 specks will be observed, which microscopically are found to consist 

 of tufts of delicate interlacing hyphse ; these, becoming interwoven, 

 ultimately form a tough mycelium. The patches of growth are 

 circular, and the hyphse will be found to radiate from the centre. 

 As the patch increases in size it changes in colour, becoming bluish- 

 green, though the margin for some time still remains white. From 

 the upper surface of the mycelium delicate aerial hyphse grow 

 upwards, and from the under surface short submerged ones project 

 downwards. 



The hyphse are composed of elongated cells arranged end to end, 

 the cell-walls of which consist of cellulose enclosing a more or less 

 vacuolated protoplasm containing several nuclei. 



The aerial hyphse are unbranched filaments, but as development 

 proceeds the distal ends branch dichotomously, the branches 

 remaining short and nearly parallel to one another, so that a kind 

 of brush is produced. The ultimate branches are known as sterig- 

 mata. The ends of the sterigmata become constricted so that little 



