470 A MANUAL OF BACTERIOLOGY 



The Fungi are divided into the Phycomycetes, Ascomycetes, 

 Basidiomycetes, and Fungi Imperfecti. The Phycomycetes are 

 distinguished by non-septate or slightly septate hyphae and zygo- 

 spore-formation, as in the Mucors. The Ascomycetes are charac- 

 terised by the development of the cell resulting from fertilisation 

 into cells, some of which become spore sacs or asci containing several 

 spores. Asexual spores are usually produced as well. The Basidio- 

 mycetes have spore-bearing structures known as basidia ; the rusts, 

 smuts, toadstools, puff-balls, and mushrooms belong to this group. 

 All fungi which do not fall into one of these three groups are placed 

 among the Fungi Imperfecti ; most of them probably belong to the 

 Ascomycetes. Mucor muiedo, Penicillium glaucum, and Asper- 

 gillus niger may be taken as types and more fully described. 



Mucor mucedo 



The Mucoracice belong to the Phycomycetes, and are divided into 

 some eighteen genera. 



Mucor mucedo, the common white mould which appears like 

 tufts of cotton-wool on various substances, may be obtained by 

 exposing some moistened bread or horse-dung to the air for a short 

 time, and then keeping it moist under a bell- jar. It consists of a 

 mycelium composed of hyphae, and its fluffy appearance is caused 

 by aerial hyphas. The aerial hyphae are at first of even diameter 

 throughout, but later on their free ends become swollen and 

 ultimately form spherical bodies, which become filled with spores, 

 the sporangia. In the early stage the whole organism forms but 

 a single cell, the protoplasm of which is granular and contains 

 vacuoles and numerous small nuclei. As it grows, and the sporangia 

 form, these become separated by a septum from the hyphae, and 

 when it becomes older stil] the mycelial hyphae may be divided into 

 elongated cells. The development of a sporangium takes place as 

 follows : The distal end of an aerial hypha swells, and immediately 

 below the swollen part a division occurs in the protoplasm and a 

 cellulose septum is formed, so that the swollen part is separated 

 off from the rest of the hypha, forming the rudimentary sporangium. 

 The sporangium continues to grow, and its protoplasm undergoes 

 multiple fission into numerous ovoid masses, the spores, each of 

 which becomes surrounded with a cellulose capsule. The septum 

 separating the sporangium from the hypha projects upwards into 

 the interior of the sporangium as a club-shaped knob known as the 

 columella. When the sporangium is ripe the slightest touch causes 

 its wall to rupture, so liberating the spores. When placed under 



