1887. | BOTANICAL GAZETTE. 177 
as yet, given satisfactory proof that the gonidia are produced 
from the hyphz or the hyphe from the gonidia; so that we 
are forced to regard them as two distinct entities. The 
strong point of the opponents of the algo-fungal theory has 
been that, if it is true that what is called a lichen is really a 
fungus parasitic on an alga, it is inconceivable ‘that the alga 
should not be injured, or even destroyed, by the fungus. It 
18 Certainly a fact that the gonidia, or alge, are not destroyed, 
and it has been assumed by both the advocates and oppo- 
nents of the theory that the gonidia are not injured by the 
Srowth of the hyphzw, while some even go so far as to say 
that their growth is aided thereby. To account for this state 
of things, the advocates of the theory have advanced the 
view that in lichens we have a sort of mutual parasitism ; 
and the statement has been made that ‘ the hyphz lie on the 
¥onidia, and carry to them crude nutritive fluids, in return 
for which they receive a part of the assimilated material in 
the gonidia.” But what good the gonidia can derive by 
having crude material brought to them by the hyphe., if they 
must give back a part of the assimilated material to them, is 
not. clear, since it is a well-known fact that the gonidia can, 
and very often do, live and flourish in a free condition, and 
are amply able to obtain all the nourishment they need with- 
out the help of the hyphez, and at the same time can use for — 
their own exclusive benefit all the assimilated material. On 
the other hand, it is known that the hyphe are dependent 
on the gonidia for their development. The advantage to the 
gonidia is quite hypothetical; the advantage to the hyphe 
's real; and it is, to speak mildly, a bad case of what the 
French call un auf pour un beuf. 
The alleged proof that the gonidia are benefited by con- 
