VI The Web of Life 109 



matic information to the text-book of Cryptogamic Botany^ 

 by Bennett and Murray (Lond. 1889). As an easy intro- 

 duction to the subject, the writer's article " Fungi " in 

 Chambers' s Encyclopcsdia may in the first place be read. 



Bacteria. — Of all parasitic plants, the smallest — the 

 microscopic Bacteria — are the most important. It is true 

 that not all of them are parasitic, for many live in rotten- 

 ness, but they all agree in being minute colourless units 

 unable to live, as green plants do, on water, salts, carbonic 

 acid, and sunlight ; able to thrive only when they find 

 organic substances of some sort ready-made for them. 



We have already seen that their presence may help to 

 explain the disappearance of flies within the traps of some 

 of the insectivorous plants, and we can detect the work of 

 bacteria in a hundred ways all around us. If we leave a 

 piece of meat or fish (whether cooked or raw matters not) 

 in an open vessel filled with clear water, this becomes 

 turbid, and a scum gathers on the surface ; if we examine 

 this scum under a high power of the microscope we see 

 incalculable numbers of bacteria. On the other hand, if 

 the piece of meat be placed in a glass flask which is filled 

 with water, then boiled for a short time, and carefully 

 closed, while still boiling, with a plug of cotton-wool, the 

 water will remain quite clear, and the flesh will not decom- 

 pose. The only difference between the two cases is that 

 in the latter the bacteria in the water have been killed by 

 boiling, and are kept out of the flask by the cotton-wool, 

 therefore we may say that the decomposition observed in 

 the first case was due to bacteria. So it is always. As 

 Huxley in aphoristic style puts it, " Putrefaction is the result 

 not of death, but of life," 



It is more than two centuries since the keen - eyed 

 Leeuwenhoek — that early devotee of the microscope to 

 whom, despite his rude and feeble instruments, the most 



