6 BOTANY. 
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. 8) may be studied again with profit. 
(0) 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, 
(@) 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 the blackish spots on the stem or leaves) for ex- 
amples of thickened cell-wall for protection. 
(f) 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. 
(A) 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. 
() 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, ete. Under a high power many 
little green balls of protoplasm may be observed. Each has a cell- 
wall. 
