514 The American Naturalist. [Tune, 
Frank also claims that the fungus exhausts the protoplasm 
of algal cells without entirely destroying them. If by this 
is meant that it does not always entirely destroy the cells it 
attacks, it is probably so, but if anything more is meant, it 
seems, like some other theories of Frank, which I shall have 
occasion to mention presently, if I may say so, decidedly 
“fishy.” Such a thing is not necessary to mutualism. The 
alga can purchase the protection of the thallus only by the 
sacrifice of a large number of individual cells. If it gets quid 
pro quo, why should it not prefer to sacrifice them to the fungus 
in return for the shelter of the thallus rather than to leave 
them victims to natural conditions without compensating 
advantage. To put the matter in another way, if the energy 
spent by the alga in producing cells to be destroyed by the 
fungus were put to making a shelter of its own, could it effect 
as much as it does by taking advantage of the thallus? 
Two other cases in the vegetable kingdom where mutualism 
is thought to exist remain to be examined. These are the 
cases of “ Pilzsymbiosis” or “ Wurzelsymbiosis” of the roots of 
anthophytes and certain fungi. The first noticed was what is 
termed “ Mycorhiza,’ and of this first. 
T. Hartig, in 1840, and others since, had noticed mycelia, 
apparently parasitic on the roots of trees. In 1885, Frank 
published the results of investigations of mycelia growing upon 
the roots of various Cupulifere in which he claimed that the 
sustenance of these trees depends upon fungi symbiotic with 
their roots. The title of his paper indicates his claim: “ Ueber 
die auf Wurzelsymbiose beruhende Ernaehrung gewisser Baewme 
durch unterirdische Pilze.” To begin with, Frank found that 
certain Cupulifere have almost the whole of their root system 
covered with mycelium associated symbiotically with the root 
and he claimed that these fungi took the place of root hairs, 
and were the only means of absorbing water, etc., possessed by | 
the roots, though, of course, like the gonidia of lichens, the 
roots could be grown independently in water cultures for years. 
The mycelia, of the existence of which there is no doubt, 
are probably connected with some of the Gasteromycetes OF — A 
Tuberacez. But Frank observes that the presence of a my eb oy 
