The Use of a Simple Microscope. 9 



accelerated by means of artificial stimulants should be gradually 

 attained, and as gradually reduced, care being taken to maintain 

 a healthy action during- the season of comparative rest, and 

 to maintain an even balance of root action and atmospheric 

 stimulus. 



The cell-structure of vegetable growth should be carefully 

 studied, as the "cell" is the fundamental unit, by a repetition 

 of which even the largest forms are constructed, and hence the 

 life of the cell is the life of the plant, and death of a part may 

 be followed by the death of the whole, unless a sufficient amount 

 of reaction can be started. 



The " mycelium " of a fungus may sometimes be traced 

 running through every part of a plant, and under these circum- 

 stances the death of the plant invariably follows. It may some- 

 times be traced only in the bark, or the epidermis, and then be 

 of less consequence. In these investigations the higher powers 

 of the microscope, as well as some acquaintance with the cha- 

 racter and habits of the parasitic fungi are indispensable.* 



But the roughness or scabbiness of roots and stems is often 

 caused by other than fungous growths ; it sometimes arises 

 from injuries inflicted by the puncture or 'presence of insects 

 — the larvae of flies and beetles ; at other times it may be 

 produced by some injurious and irritating cause connected 

 with the soil. A small transverse slice cut very thin by 

 means of a sharp razor, and examined in water between two 

 pieces of glass, will show the disposition of the cells both 

 healthy and injured, and how far the latter extend, or are con- 

 nected with the general structure. Transverse sections of the 

 leaves taken through a diseased spot, and examined edgewise, 

 show also to what extent the cells of a leaf may be affected by 

 disease. 



The leaf itself is an important study, and requires some little 

 amount of patient investigation to be thoroughly understood, but 

 without this knowledge it is utterly impossible for any one to 

 appreciate the exquisitely beautiful and delicate offices it has to 

 perform, and the means by which its functions are carried on. 



StauCH-CELLS. — If a very thin slice from the interior of a 

 healthy potato be placed between two pieces of glass, squeezed 

 out, and then examined with a magnifying glass, there will be 

 seen an infinite number of little oval shining bodies of many 

 different sizes. These are starch-cells, and should form almost 



* A knowledge of these may be acquired by the aid of M. C. Cooke's ' Plain 

 and Easy Guide to the Study of Microscopic Fungi.' 8vo., coloured figures, 

 piiee G.S. Hardwicke. 



