40 THE BIOLOGY OF THE CELL 



buildings, on the outside of damp flower-pots, etc. They 

 will be most easily found after a few days of rain ; at 

 other times their bright green color is likely to be dingy 

 and not so noticeable. If the plants be found on a tree, 

 cut off pieces of the bark and put them in a saucer with 

 a little water to moisten the bark, cover with a tumbler, 

 and set them in a window where they will have the 

 sunlight. In this manner a supply of fresh specimens 

 may be kept for a long time and the various stages of 

 growth studied from time to time. This method of 

 procedure is advisable, as it is sometimes impossible to 

 And material showing both the vegetative and the re- 

 productive stages of the plant. Besides the specimens, 

 the student Avill need strong iodine, alcohol, seventy-five 

 per cent, sulphuric acid, dilute chlor-iodide of zinc, and 

 a compound microscope ; also some cotton fibres, which 

 are best obtained from a cotton-boll, as they have then 

 passed through none of the processes incident to manu- 

 facture, and are in a perfectly natural condition. If the 

 boll cannot be obtained, fibres from a thread or from a 

 piece of cotton cloth may be used. 



Method of Examination. — Before resorting to the 

 microscope examine, as directed on page 41, the naked- 

 eye characters. If the material be obtained from a very 

 damp situation, a small piece of the mud or of the film 

 of slime may be put upon the slide, in a drop of water, 

 and torn to pieces with the dissecting needles, so as 

 to separate the cells of the plant from the tangle of 

 thread -shaped algge and fungi, associated with which 

 the green slime almost always grows. If the material 

 be dry and powdery, as it is likely to be if obtained 

 from bark in dry weather, a little of the film may be 

 scraped into a drop of water on a slide by means of 



