8 The Use of a Simple Microscoj^c. 



sources of plant health and strength are obtained by means of 

 the capsules or spongioles, the termini of every root and rootlet, 

 and also by the absorbent cells ever found at the extremities 

 of the numberless suckers ; for it is at these points that I find the 

 cell-structure very greedily taking in whatever foreign matter 

 1 have succeeded in introducing into the media in which 1 have 

 grown the plants. The action of anything placed in the medium 

 in which plants grow which is injurious to them, is at once 

 shown by its action upon their roots and lateral processes, the 

 capsules losing many of the characteristics of healthy action. . . . 

 There can be no doubt but that the plant requires not only 

 certain chemical constituents to secure its health, but that these 

 must be offered to it when growing in a medium, allowing the 

 utmost freedom to the capsules of the roots, rootlets, and to the 



suckers I am satisfied a highly pulverised poor soil 



would grow better plants than a close, hard, tenacious soil, 

 however fertilised." 



It is, then, to the terminal points of the roots and rootlets 

 that the inquirer's attention must be directed, and for this pur- 

 pose the microscope is invaluable, as affording at a cheap rate 

 that information which obtained in the field on a large scale 

 becomes a costly experiment.. 



The discovery of a patch of fungus upon the leaf or stem of a 

 plant must not be taken for a cause of injury to the plant; it 

 generally only indicates a want of vital action, and is the con- 

 sequence of decaying organic matter. Fungi are rarely, if ever, 

 found on healthy surfaces, but it is a law of nature that nothing 

 stands still ; if a plant be growing freely and healthily, it holds 

 its own, and no sporadic fungi find a location, but the moment 

 vital action flags or ceases, either from decreased vital energy, or 

 from local injury, a lower order of vegetation instantly com- 

 mences to obtain a sway. Mildew generally shows itself after a 

 season of active growth, followed by an inequality in the supply 

 of moisture from the soil and from the atmosphere. In other 

 words, when from drought but little moisture finds its way into 

 the system through the medium of the roots, such amount being 

 insufficient to maintain a full and active circulation icithin the 

 plant, and when the vital action thus becomes sluggish, the dews 

 and damp of the night air overbalance it, and the germination 

 and growth of fungi then commences. 



Fungi are known to be rapidly developed during and imme- 

 diately after a thunderstorm, owing, it is supposed, to the nitro- 

 genous compounds formed in the air, as a result of these elec- 

 trical discharges. Hence upon this hypothesis the application 

 of a stimulus to the roots should take place whenever any exces- 

 sive stimulus is being derived from the atmosphere. Growth 



