PLATE I. 



THE YEAST PLANT. 



Fio. 1. Showing — 



C Cell-wall or sac. 

 A Ckm, J Protoplasm (Gr. protos, first; plaama, from pJasso, to mould). 

 ( Vacuole tilled with cell-sap (L. vacuum, an empty space). 

 Fu;s. 3, 3, and 4. Showing — 



Multiplication by Budding or Gemmation (L. gemma, a bud). 



The commencement of the process is seen in fig. 2. A bit of protoplasm is pushed out, 

 stretching the cell-wall and making it tliin. Pig. -i shows a cell aggregate or colony produced 

 by a repetition of the process of budding. 

 Fio. 5. Showing — 



Multiplication by Endogenous Division (Gr. ew.lon, within; gennao, I produce). 



The protoplasm collects usually into four round masses, each of which takes on a cell-wall. 

 Cells produced in that way are called Ascospores (Gr. a-slcos, a bag; spora, a seed) or Eudo- 

 conidia (Gr. endon, within; konis, dust). 

 Fio. n. Showing — 



As'cosPORES set free by rupture of the cell-wall of parent, and multiplying by gemmation. 

 Fig. 7. Effect of — 



Magenta — Stains protoplasm, leaving cell-wall comparatively unstained. 



Crushing — Ivuptures the cell-wall, and shows that the cell-wall is tougli and resisting, while the 



protoplasm is semi-fluid. 

 Potash (KHO) — Dissolves out the protoplasm. 

 Iodine — Stains protoplasm. 

 Fig. 8. Measurement by eyepiece micrometer. 



Diagram I. Physiology— 



a. Shows the composition of a fluid fit to nourish j'east (Pasteur's fluid). 



Elements which make cell-wall (C.O.II.). 



Elements which make protoplasm (C.O.H.N.). 



Elements which make ash (P.S.K.Mg.Ca.). 



h. Shows the composition of the fluid when acted upon b^' yeast. Process of fermentation 



{/erveo, I boil). 



/ Carbonic acid (CO.^). 



Sugar becomes I Alcohol. 



(. Small quantities of succinic acid and glycerine. 



About two per cent, of sugar is unaccounted for. 



Ammonium tartrate, etc., used up by the yeast. 



rp , , u { ^Nfauulacture of alcohol and carbonic acid. 



Total result ■ •' ^ ^ ^ ,, „ , 



{ .Manufacture of cell-wall and protojilasm. 



CLASSIFICATION OF YEAST. 



KbujiJom — Plantie, because it possesses a cell-wall made of cellulose, and can wianufacturc 



protojilasm. 

 Suh-Kingdom — Thallophyta, because it possesses neither root, stem, nor leaf. 

 Vldss — Protophytn, because it has no sexual process of multiplication (Gr. proion, first; phytoii, 



j)lant). 



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