and its Mycorhiza,. 357 
to the host as a fungus-digesting plant ( pilzverdauende 
PJianze). 
Having dismissed the first part of Frank’s view as to the 
biological significance of endotrophic mycorhiza, the second 
question arises, ‘ Is there any sufficient reason for his assump- 
tion that the physiological meaning of the endotrophic is 
different from that of the ectotrophic mycorhiza ? 5 Three 
series of facts all point in the same direction in answer. First, 
all known holosaprophytes (with one exception ?) possess 
mycorhiza ; but it may be either ectotrophic ( Monotropa , &c.), 
or endotrophic (Orchids, &c.). Secondly, in Ericaceae, Epa- 
cridaceae, &c., though the mycorhiza is endotrophic, the 
hyphae do not penetrate deeper than the superficial cells 
of the root. This type may be regarded as affording a transi- 
tion-stage between the complete endotrophism of Orchids and 
Thismia , and the ectotrophic condition of Monotropa , forest- 
trees, &c. Thirdly, in endotrophic mycorhiza it is often the 
case that many hyphae radiate out into the substratum ; on 
the other hand, in the ectotrophic mycorhiza, hyphae frequently 
penetrate the superficial cells of the host’s root (at any rate in 
older parts of the root) ; and in the ectotrophic mycorhiza of 
Pinas roots, which is occasioned by Polysaccum 1 , some of the 
hyphae actually dip deep into the tissue of the root, at the 
same time absorbing so vigorously as to play havoc with the 
infected tissues. Thus in ectotrophic mycorhiza the hyphae 
are not always epiphytic, nor in endotrophic mycorhiza are 
they exclusively endophytic. 
Hence the distribution of the tivo forms of mycorhiza and 
the occurrence of transition-stages between their extreme forms 
militate against the view that the physiological significance is 
not the same in both . They both probably work in one general 
constant manner. Mycorhiza is, then, either a highly adapted 
and symbiotic community beneficial to both symbionts, or it 
is a pure matter of infection of a plant by a Fungus, and there 
is a constant struggle between host and the would-be parasite. 
1 E. Bruns, Beitrag zur Kenntniss der Gattung Polysaccum. Flora, 1894, 
pp. 67-75. 
