289 



THE ORIGIN AND TENDENCIES OF 

 PARASITISM IN FUNGI.* 



G. MASSEE, F.L.S., V.M.H., etc. 



It is now generally admitted that parasitism in an acquired 

 habit on the part of fungi. One of the accepted proofs is the 

 fact that fungi that are only known as pure saprophytes, can 

 by a judicious course of training, be taught to become rampant 

 parasites, and can afterwards be coaxed back to their original 

 condition of saprophytism. On the other hand, fungi that at 

 the present day are only known as parasites, can be educated 

 to live on dead organic matter, or in other words to change their 

 mode of life and settle down as saprophytes. From the stand- 

 point of food or nutrition, fungi at the present day may be 

 arranged under three groups, i. — Pure saprophytes, or those 

 fungi that obtain their food from dead organic matter, as dead 

 wood, humus, etc. The common mushroom, and many toad- 

 stools that grow on rotton wood, dead leaves, etc., are examples. 

 2. — Compulsory parasites, that can only obtain their food from 

 living plants or animals, as the rusts and smuts of cereals, 

 ringworm, and the white fungus that forms a halo round a dead 

 fly on a window-pane, are representatives of this group. 3. — 

 A whole host of fungi that occupy a transition stage between 

 groups I and 2, and are capable of living as saprophytes 

 or as parasites respectively, depending on circumstances. 

 Such fungi are considered as not having as yet perfected the 

 various methods necessary to enable them to lead a truly 

 parasitic life. A typical example of this group is furnished by 

 the universally distributed, mouse-coloured mould called 

 Botrytis chierea, which is in reality the conidial condition of a 

 Peziza or cup-shaped fungus. 



The following experiments in the education of fungi, or 

 weaning them from one habit, and teaching them to take up 

 another, were conducted in the Jodrell Laboratory at Kew. 

 The spores of certain fungi known only as saprophytes, of 

 which Trichothecium roseum, may be given as an example, were 

 mixed with a solution of the substance on which they normally 

 grow. This solution with its contained spores, was injected, 

 by means of a hypodermic syringe, into the living leaf of an 



* Abstract of an Address given at the Annual Fungus Foray of the 

 Yorkshire NaturaUsts' Union at Castle Howard. 



1910 Aug. I. 



