288 VINEGAR PLANT. PAET n. 



develop themselves into rows of four or five globes, which 

 remain in contact while the plant is growing, but sepa- 

 rate if anything checks the fermentation. The full 

 development of the plant only takes place when the 

 fermentation is allowed to continue for some time, and 

 then it is capable of producing a variety of forms, which 

 show that it has other modes of reproduction besides 

 budding. 3 In fact, when the fermentation is active in 

 the upper parts of the liquid it appears in chaplets of 

 from four to twelve articulations, or sometimes it rami- 

 fies into little branches. 



More recent observations show that yeast is a peculiar 

 state of the mycelium of various fungi, of which, as 

 already stated, a large proportion is believed to consist 

 of Penicillium glaucum, though it is known that other 

 kinds of mould also enter into its composition. These 

 plants grow naturally in a state of exposure to the 

 atmosphere, but they have the property of also develop- 

 ing themselves when submerged ; and as in this un- 

 natural condition, which they bear when developed as 

 yeast, they cannot produce their proper fruit, they pro- 

 pagate themselves by means of shoots from the altered 

 mycelium. It has been observed that mechanical injury 

 destroys the vitality of German yeast, which consists of 

 yeast globules in a dried state. Thus a fall on the 

 ground, or a bruise caused by a blow or by careless 

 handling, will kill the plant, and such dead yeast 

 becomes dark-coloured and glutinous, and soon ac- 

 quires an offensive smell. 



The form of Penicillium glaucum which produces 

 acetic fermentation, known as the vinegar plant, has a 

 filaniental submerged instead of a vesicular mycelium. 



Ferments may be formed in the wort of beer, in the 

 solutions of grape and cane sugar, in the juice of goose- 

 berries, currants, &c., by means of the submerged spores 



8 ' The Microscope,' by Dr. Carpenter. 



