140 TIMBERS AND THEIR USES 



There is an intermediate class of plants known 

 as partial or semi-parasites of which the Mistletoe 

 is a good example. These semi-parasites steal 

 some of their food from their hosts and, being 

 provided with green chlorophyll laden leaves, 

 elaborate the rest of their food from the air. 

 It is clear that as they contain chlorophyll they 

 are not fungi. We will consider them here, 

 however, for convenience' sake, just as we studied 

 the ship worm along with the insects. 



With saprophytes we are not immediately 

 concerned ; parasites are the organisms causing 

 disease. When present in small numbers they 

 may do no great harm, but there is always the 

 danger that they may increase rapidly and so 

 set up a condition of disease. 



The various forms of fungoid pests cannot be 

 described in a few words. In general it may be 

 said that they are either external or internal, 

 that is they either grow upon the surface of 

 their hosts or actually in their tissues ; they are, 

 in short, either ecto or endo-parasites. As a 

 rule the vegetative portion of the fungus con- 

 sists of a mycehum, that is a threadUke growth 

 forming at times a dense matted structure which 

 either chokes up the tissues of the host in the 

 case of an endo-parasite or ramifies over its 

 surface if it be an ecto-parasite. Reproduction 

 may take place vegetatively (i.e. portions of the 



