THE MICROSCOPE AND CELL-STRUCTURE. 69 



we may use any aniline stain (e.g. aniline blue or violet) for lignified 

 walls, and carmine instead of haematoxylin. 



In any case, the stain, dissolved in water or alcohol, is applied in 

 drops to the specimen on the slide, or the specimen is dipped into the 

 staining solution in a watch-glass and lifted out after some minutes 

 with a brush ; the stained specimen is then washed with water or 

 alcohol, and if necessary placed in a second staining solution for double 

 staining, e.g. safranin and haematoxylin, or aniline blue and carmine, 

 and finally mounted. 



Ready-stained preparations (sections of stems, roots, leaves, etc.) 

 can be bought. The Plant Biology Collection of Microscopic Slides (see 

 Preface) contains a good selection of preparations. 



QUESTIONS ON CHAPTER III. 



1. Describe the parts of a compound microscope, with a sketch 

 showing the parts labelled. What is the use of a nosepiece, a cover- 

 glass, a concave mirror, a draw-tube ? 



2. Describe the structure of a young parenchymatous cell and 

 explain how it differs from that of a fully-grown cell of the same kind. 



3. How would you obtain a living green cell for examination with 

 the microscope? Describe, with sketch, the appearance of the cell, 

 mounted in water. 



4. How would you obtain, for mioroscopio examination, a living but 

 not green cell ? Sketch the cell as seen (a) in water, (6) in salt solu- 

 tion, (c) after treatment with iodine solution. 



5. Describe and sketch the cells seen in sections of (a) Bean cotyle- 

 don, (6) Date stone, 



6. Describe the circulation of protoplasm as seen in any living cells 

 you have examined ; name the plant used and sketch one of the cells. 



7. Describe and sketch the appearance of a cell of Spirogyra, (a) in 

 water, (6) in salt solution, (c) after treatment with iodine solution, 

 (d) after treatment with alcohol. 



8. Describe, with sketches, what you have seen (i) with naked eye 

 and lens, (ii) with the microscope, of (a) the structure of a grain of 

 Wheat or Maize, (6) the origin of a rootlet, (c) the structure of a young 

 stem, e.g. Sunflower. 



9. Make a drawing of some living green cell which you have your- 

 self observed. Name the various parts you figure, and state in a few 

 words the use of each in the life of the cell. How was the cell 

 obtained and prepared ? By how many diameters does your drawing 

 magnify the size of the original ? * 



