160 LABORATORY STUDIES OF CRYPTOGAMS 



362 (Compound). Bacteria. — With a needle transfer to a slide a 

 bit of the scum that gathers on water in which vegetable matter is 

 decaying. Cover with a cover glass and examine with a high power. 

 The Bacteria are glistening white (i.e. colorless) bodies of small size 

 often occurring in broad j)atches of gelatinous matter (the matter 

 which holds the " scum " together) in which they are more or less 

 evenly spaced ; or occurring in chains or threads. Some may be spiral 

 in form and exhibit very active motion. Having found the Bacteria, 

 remove the cover glass, sjDread the scum out thin on the slide, and 

 dry this preparation by holding it at some distance above a flame. 

 When the last bits of the spread scum are about to become dry, 

 remove from the heat and add drops of gentian violet stain. ^ After 

 a moment wash this off with a little water, cover, and reexamine. 

 The various forms, now more plainly seen, are to be drawn. 



For suggestions as to the biological study of Bacteria see Appendix. 



363 (Compound). Yeast. — Mount in water a small bit of yeast 

 cake, spreading the material out thin, and examine with a high power. 

 Are the yeast plants of uniform size? Have they any peculiarity of 

 form, common to all, or nearly all (i.e. are they uniformly spherical, 

 or elliptical, or ovate, etc.) ? Have they any common features of 

 internal structure ? Having determined these points in jour own 

 mind, make a drawing of a typical yeast plant of the species you have, 

 the drawing to be large enough to show easily any internal features.^ 



364 (Compound). From material that has been growing for a few 

 hours in sweetened water (a teaspoonful of sugar to a half glass of 

 water), study the method of multiplication. Do the buds — the new 

 individuals growing out from the bodies of the old plants — spring 

 from any particular region, as a rule ? Draw in outline three stages 

 in the budding process. 



365. Is any action of the yeast upon or in the sugar solution 

 to be seen? To test this, drop small pieces of yeast cake into tum- 

 blers of (1) sugar solution, (2) water alone. In fifteen minutes or 

 so the result should be observable, and within an hour very marked. 

 What bearing has the action observed upon the utility of yeast plants 

 in bread making? Answer this question in your notes on this 

 experiment. 



366 (Simple). Bread Mold (Rhizopus nigricans). — Use the hand 

 lens to examine the moldy bread without disturbing it, so as to see 



1 Strong eosin solution may be used, and it leaves the Bacteria with a 

 more lifelike appearance, though not so sharply detined. If the prepara- 

 tion is stained with gentian violet, washed, and thoroughly dried, Canada 

 balsam may be used upon it and the preparation thus be made permanent. 



2 The teacher should draw upon the board the characteristic form and 

 striations of starch grains to be found in the yeast caHe, so tnat they may 

 not be mistaken for the yeast plants. 



