ECONOinC MTCOLOGY. 289 



introduced boiled grape juice into a series of thirty flasks ; of these ten 

 were immediately sealed up ; into a second ten he di-opped a minute 

 quantity of hquid prepared by washing the sui-face of some ripe 

 untouched grapes ; into the third ten he passed some of the same hquid 

 boiled. In forty-eight hours the fii'st ten were unaltered, the second ten 

 were in full f fermentation and filled with flakes of myceUum, the third 

 ten were unaffected. There is reason for beheving that all saccharine 

 fruits have on their surface spores which remain quiescent till a con- 

 currence of circumstances brings them into contact with the enclosed 

 juices, then subaqueous growth commences accompanied by the decompos- 

 ition of the sugar. So long as the subaqueous growth contuiues propaga. 

 tion of the fungus takes place by budding, but as soon as the sugar is 

 exhausted thefungus comes to the surface and forms spores. Saccharoimjces 

 cerevisUv, or common yeast, is seen under the microscope to consist of a 

 multitude of gi-auular cells, diffused thi-ough a turbid hquid called yeast 

 water. The cells ai-e about 1-3,000 of an inch in diameter, and, hke all 

 other vegetable cells in their simplest stage, consist of a speck of jelly 

 called protoplasm, enclosed in a non -nitrogenous envelope. Yeast is 

 composed principally of albuminous and amylaceous matter, but it 

 contains a large proportion of phosphates of potash and magnesia. The 

 remai'kable feature in its composition is its richness in nitrogen. 

 Funguses contain more nitrogen than any other class of plants. The 

 Chantarelle contains 3-62 per cent., Boletus edulis 4-2.5, Lactarius deliciosus 

 4"60, mushroom, 7"26, and yeast 10, so that it closely approaches animal 

 matter. These Agarics have been selected for comparison because they 

 have been often set before us at our Fungus Foray dinners. Knowing 

 the chemical composition of yeast, we should expect the medium in 

 which it flourishes to contain the nitrogenous and mineral matters which 

 it requires. It has been proved by experiment that yeast %\ill not exert 

 its pecuhar action on sugar unless these matters are present in solution. 



"We all know that if yeast be added to a hquor at a suitable 

 temperature in which malt or some saccharine fi-uit has been digested, 

 certain occurrences will ensue. The hquor will shortly become turbid 

 effervescence will take place from the escape of free carbonic acid, the 

 sweetness will disappear, alcohol will become evident to the taste and 

 smell, and a large increase will take place in the bulk of the fungus. 



There are several varieties of sugar much alike in their chemical 

 composition and properties. The two principal are saccharose and 

 glucose. Yeast acts differently on each, so that it will be well to trace 

 back their relation to, and formation from, starch. Starch, chemically, 

 is nothing more than carbon, combined with the elements that comj)ose 

 water in the proportion of six to five. It appears to be the first product 

 of that decomposition of carbonic acid and assimilation of the cai'bon, 

 which, under the influence of the sun's rays, is continually going on in. 

 growing plants. Starch is the basis from which most other vegetable 

 secretions are formed. It is either used up at once by the plant that 

 secretes it, or it may be laid by for futmre use ; sometimes in the tuber 

 as in the potato, in the seed as in com, or in pith as sago. Saccharose, 



