PLANT DISEASES. 



729 



particular way in which such infection occurs, and the duty of the 

 gardener to become acquainted with such discoveries to the extent neces- 

 sary for practically combating the infection. 



(2) If I have succeeded in demonstrating the presence of fungus myce- 

 lium in the tissues of plants under conditions where it would not be 

 suspected -by the gardener, it follows that a disease may be, is in fact, 

 often propagated unconsciously. For example, if a Pink showing smut 

 in the anthers is used for "layering," remembering that the mycelium 

 passes up from the root through the stem to the flower, the probability 

 is that every plant produced will be diseased. It is well to avoid using, 

 for vegetative modes of reproduction, portions of any plant showing an 



Fig. 306. — Orchid Leaf-kust {Gloeosjjorium cinctiim). . 



The mycelium is present in the leaf for some time before it appears in a fruiting 

 condition on the surface, as shown in fig. 1. 2. Pustules of fungus, slightly x . 

 3. Coniilia of fungus oozing out of the leaf in a tendril. 4. Section through a 

 fungus fruit imbedded in the leaf. 5. Conidia of fungus, x 400. 



outbreak of fungus fruit on its surface, as in many instances the myce- 

 lium extends far beyond the point where it bursts through the tissues, 

 and portions of the plant that might be considered sound may in reality 

 contain mycelium, and if so diseased plants would result. 



(3) Lack of cleanliness in matters of detail, as to dealing with frag- 

 ments of diseased plants. It is sometimes felt that a dead plant can do 

 no harm ; this, however, is not the case if the plant has been killed by a 

 fungus. In such instances spores are undoubtedly present, and do not 

 die when the host-plant dies, but are dispersed by wind and lodge in nooks 

 and crevices, and at the proper time commence to germinate and renew 

 the trouble. Burn all fungus-diseased plants as soon as they are realised 

 to be useless, and do not leave them in some corner indefinitely. 



