176 BOTANICAL GAZETTF. [ August, 
sight a parasite would seem to be purely destructive in its 
action; and that this is really the case is evident in the great 
majority of instances. When a piece of bread is attacked 
by the mould, Mucor stolonifer, its substance continually 
diminishes with the growth of the mould. We need not stop 
to consider the saprophytes, for the case of the true para- 
sites is still stronger. There is a constant struggle between 
the rots, rusts and other true parasites and the hosts om 
which they are growing. Just so far as the fungus flourishes, 
so does the host suffer; and, if the conditions of temperature 
and moisture are favorable to the fungus, the host may De 
uite destroyed. If the conditions are not favorable to the 
An instance of the sudden and complete destruction of the 
host is seen in the case of the bad epidemics of the potato 
young seedlings, some of which are-destroyed, while others 
~ 
parasites which are less virulent and whose action is more 
local. e have all grades of injury done to the host, from 
the destruction of the leaves and consequent diminution 
the assimilating power, which may entail seriou 
results; from the formation of circumscribed Knots and 
tumors, which may cause destruction of the branches and, 
Site is destructive. We can not conceive that it 18 0b d 
“ere host. It robs the plant of the foot 
Which it needs for itself, and gives back nothing good 1 
return, : : 
; We have, on the other hand, instances of parasitism Ne 
which it is claimed that the relation of parasite and host* 38 
0s asec prareee ns 
t organ 
2 The word * symbi Py . 
s osis’”’ was ori ll lied here differen 
w ‘ ‘ ginally applied to all cases whe 
The, ‘aot «pony together in a community, aon in this sense included the true . 
ally muidoees a has atadibally been modified until vi biosnimals, 
suc : “an | oe n nts with 
hoi ol ee between them is one of mutual benefit, or in Wile 
¢ on of one o is r. this sens 
with true barasitism, the word is here — dates Pete usiae 
rast 
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