12 Reproductive Organs. 



If the loose spores are examined as to their individual structure, whether 

 aecidio uredo or teleutospores, it is simply necessary to mount them 

 direct, and 1 lind the most convenient mounting medium to be glycerine 

 and water in equal proportions. For permanent preparations glycerine 

 jelly may be preferable; but for the rapid examination of material the 

 above serves very well, and where desirable the mount can be preserved. 

 The surface markings of the spores are often obscured in mounting, and have 

 sometimes been overlooked by otherwise good observers. As a general 

 rule, they are best seen in the dry condition and without any special pre- 

 paration, but they are usually also seen in glycerine and water, especially 

 if examined when freshly mounted. 



The number and position of the germ-pores require to be carefully 

 studied, since they are often of specific value, and there are various re*- 

 agents which show them up with great clearness. Among these, I have 

 successfully used lactic acid and Bismarck brown. 



A 50 per cent, solution of lactic acid was used as a mounting medium, 

 then the spores were added, and the slide was heated over a spirit-lamp 

 just until the liquid reached the boiling point. Sometimes it is necessary 

 to boil for a little in order to get the best results, taking care, not to 

 burst the spores, but as a rule bringing it to the boil is sufficient. After 

 the preparation has cooled, the cover-slip is placed over it. Some, use a 

 mixture of equal parts of glycerine and alcohol for mounting the spores 

 before adding the acid. 



Boiling in lactic acid not only drives out the air and makes the, spores 

 more transparent, but it swells them to their normal shape and size, and 

 not only brings out the germ-pores, but the surface markings as well. Por 

 pale-coloured spores or spores which have partially lost their colour 

 through age, I have found nothing to surpass Bismarck brown. The 

 clear germ-pores show up well against the brown stain. The spores are 

 simply laid in the smallest possible amount of water or water and glycerine 

 on a slide, then thoroughly separated by stirring with a needle. Sufficient 

 of the stain is next applied, covered, and after gentle boiling the spores 

 are ready to be examined. It stains quickly, but does not overstain, and 

 is fairly permanent. 



Soaking hard tissues for twenty-four hours in a solution of caustic 

 potash or caustic soda softens them wonderfully, and mounts made from 

 minute pieces of the material thus treated are often extraordinarily beauti- 

 ful, and the relation of the parts to one another is preserved in a surpris- 

 ing manner. Though soaking for several days nearly always destroys the 

 colour of the spores, yet details may sometimes be distinguished with a 

 certainty not obtainable by any other method. 



For determining the average size and shape of the spores I know 



nothing better than photography. Numbers of spores are photooraphed 



ier, and the general shape can be determined by comparison while 



size is deduced from the exact measurement of individuals in large 



In this way the average size has been obtained for the teleu/to- 



res chiefly, of all the species accessible for observation. At the same 



ge number were measured direct by an eye-piece micrometer 



and I the results compared. All the microscopic investigations were irade 



