I 9 6 TEXT-BOOK OF FUNGI 



growing members of the Ustilagineae in nutrient media 

 under special conditions. On the other hand, I have 

 succeeded in inducing fungi only known in nature as pure 

 saprophytes to become true parasites. Notwithstanding 

 the above and much more evidence in existence on the 

 same subject, I am more than doubtful as to whether such 

 evidence is in reality as convincing as it appears to be at 

 first sight. 



It is always the outcome of so-called pure cultures, and 

 this fact alone suggests to my mind when dealing with 

 fungi a suspicion of doubt, not doubt as to the fact of its 

 being a pure culture ; this point with present day appliances 

 can be assured. The doubt arises from the conditions 

 under which pure cultures are at present necessarily 

 conducted. Suppose an infection experiment on a given 

 plant is the object in view, to secure an uncontaminated 

 host, the seed is sown in sterilised soil and placed under a 

 bell-jar, which is never removed except fora moment when 

 the spores of the fungus are placed on the young plant. 

 Is such a host normal in every respect? Would a gardener 

 desiring healthy, hardy plants, of the kind experimented 

 with, grow them under those conditions ? It is very 

 doubtful whether the physiological condition of the host- 

 plant under such abnormal conditions can be similar to 

 those of a plant of the same kind grown under normal 

 conditions, and if this be true, to what extent does the 

 experiment teach us as to what taes place under natural 

 conditions ? 



The result must necessarily be less convincing when 

 detached parts of plants or even isolated leaves are used 

 for pure cultures. Under such conditions it is difficult to 

 conceive that the varied constituents of the cells continue 



