196 



Methods in Plant Histology 



To show the structure of oospheres and antheridia, sections must 

 not be thicker than 5 ju. Sections as thick as 10 to 15 ju may be 

 cut to show the position of oogonia and antheridia, although such 

 sections are too thick to give satisfactory views of the nuclei. 



HEMIASCOMYCETES 



Saccharomyces. Formerly it was considered rather difficult to 

 demonstrate the nucleus of the yeast cell. With fresh growing yeast 



the following method by Wager should be 

 successful: Fix in a saturated aqueous 

 solution of corrosive sublimate for at least 

 12 hours. Wash successively in water, 30 

 per cent alcohol, 70 per cent alcohol, and 

 methyl alcohol. Place a few drops of 

 alcohol containing the cells on a cover, 

 and when nearly dry add a drop of water. 

 After the yeast cells settle, drain off the 

 water and allow the cells to dry up com- 

 pletely. Place the cover, or slide, with its 

 layer of ceils in water for a few seconds, 

 and then stain with a mixture of fuchsin 

 and methyl green, or fuchsin and methyliii 

 blue. Mount in glycerin or in balsam. 



ASCOMYCETES 



This group, popularly known as the 

 "sac fungi," contains an immense number 

 of saprophytic and parasitic forms. The 

 green mold on cheese and leather, the leaf 

 curl of peach, the black knot of cherry and 

 plum, and the powdery mildews are familiar 

 to everyone. The few objects selected will 

 enable the student to experiment, but he 

 must not be discouraged if success does 



not crown the first attempt, for some members of the group present 



real difficulties. 



FIG. 52. Peziza odorata: 

 three asci and many para- 

 physes; fixed in corrosive 

 sublimate, stained in bulk in 

 alum carmine, teased out, 

 and mounted in balsam. 

 X245. 



