32 A HALF-HOUR WITH THE 



attached, and placed under the Microscope, it 

 will be found to consist of a number of sepa- 

 rate minute cells (Fig. 84, PL 4). This plant 

 belongs to the same family as the red-snow plant, 

 and there are a number of forms of these minute 

 organisms, which, on account of their rapid growth 

 and red colour, have given rise to alarming appre- 

 hensions, in former times, when their true nature 

 was imperfectly understood. One of them attacks 

 bread, and gives to it the appearance of having 

 been dipped in blood. Of the same simple structure, 

 but not having a red colour, is the yeast-plant, or 

 fungus (Fig. 85, PL 4). This plant abounds in 

 yeast, and may also be found in porter and ale. If 

 vinegar is allowed to stand for some time, a minute 

 plant is developed, called the vinegar-plant. In its 

 earlier stages of growth it exhibits elongated cells, 

 looking like broken pieces of thread (Fig. 86, PL 4). 

 Threads more fully developed are often seen in 

 decomposing fluids, and upon the surface of de- 

 composing animal and vegetable substances (Fig. 87, 

 PL 4). Such plant-like threads can be collected 

 from the air in damp and unwholesome cellars 

 and rooms, and were at one time supposed to be 

 connected with the production of that fearful 

 disease, the cholera. It has been rendered, how- 

 ever, exceedingly probable that all these appear- 

 ances are but different forms of the fungus which 

 produces common mould, and which is known by 

 the name of Penidllium glaucum (Fig. 90, PL 4). 

 This plant may be found on the surface of pre- 

 serves and jellies, and consists of a mass of fila- 

 ments or threads serving as its base, from the 

 surface of which filaments rise up, bearing a number 

 of minute cells which are the spores, or reproductive 

 organs (Fig. 91, PL 4). 



Plants such as these, and belonging to the family 



