6 BOTAJST. 



they may differ in external appearance, we shall always 

 find that they are made up of cells alike in all essential fea- 

 tures. Thus the simple Green Slime of the rocks is com- 

 posed of a single cell, the homologue of which is repeated 

 millions of times in the giant oak of the forests. 



Practical Studies.— {a) Mount a leaf of a moss for a good exam- 

 ple of cells showing their walls. The sections of root-tips previously 

 mentioned (p. 3) may be studied again with profit. 



(6) For thickened cell-walls make sections of the shell of the 

 hickory-nut or cocoa-nut. 



(c) Make longitudinal and also cross sections of apple-twigs; some 

 of the pith-cells show thickened walls marked by dots and pits. 



{d) Make longitudinal sections of a stem of Indian corn, so as to 

 obtain very thin slices of some of the threads which run lengthwise 

 through it. Cell-walls showing rings, spirals, and reticulations may 

 be readily found (Fig. 3). 



(«) Mount spores of the "black rust " of wheat or oats (by carefully 

 scraping off one of llie blackish spots on the stem or leaves) for ex- 

 amples of thickened cell-wall for protection. 



(/) Mount pollen-grains of mallows or squashes for thickened 

 wall which has developed projections externally. 



{g) Make longitudinal sections of the young part of a root or stem, 

 stain with carmine, and after a little time note that the nucleus shows 

 distinctly in each cell. 



Qi) For large cells examine the parts (leaves and stems) of water- 

 plants. In the Water-net (Hydrodictyon) they may be seen with the 

 naked eye. 



(j) For very small cells mount a minute drop of putrid water and 

 examine with the highest power of the microscope available. Myri- 

 ads of minute cells, each a single plant, will be seen darting hither 

 and thither in the water. These are the Bacteria, to be more fully 

 noticed in Chapter VII. A. tumbler in which leaves and twigs have 

 been allowed to begin to decay will furnish good material. 



(J) Slime-Moulds may frequently be found on rotten logs, on de- 

 caying planks of wooden walks, or on the "spent bark" of tan-yards. 

 The common one is a yellowish mass, often ten to twenty centimetres 

 long. 



(k) For Green Slime scrape off a little of the green slimy growth 

 to be found on damp walls, rocks, etc. Under a high power many 

 little green balls of protoplasm may be observed. Each has a cell- 

 wall. 



