336 Ward. — Recent Publications bearing on the 
are as delicate as those inside ; they often stretch from the 
root to the neighbouring turf and humus remains. 
Although all plants investigated had the fungus somewhere 
at the roots, still branches of the roots here and there were 
devoid of mycelium inside or out. The fungus is to be re- 
garded as constantly present on Andromeda polifolia , Vac- 
cininm Oxy coccus, Ledum palustre , Vaccinium idiginosum , 
Empetrum nigrum , and also the American moor-plant Vac- 
cinium macrocarpum. Numerous other moor-plants showed 
no traces. 
Further research showed the presence of the fungus on 
Calluna vulgaris , Vaccinium Vitis idaea , V. myrtillus , and even 
on some specimens of Rhododendron ponticum and Azalea 
indica. On the other hand, the mycelium was not present 
at the roots of Pyrola — a statement which corrects Kerner’s 
short announcement (Sitzung. d. Akad. d. Wissensch. in Wien, 
4 Mar. 1886 : see footnote to Frank’s paper, p. 401) that he 
had found the fungus on all Pyrolaceae, Ericineae, and 
Vaccineae. 
The Mycorhiza of Monotropa is, as we have already seen, 
an ectotrophic form, agreeing with the typical form found 
on the Cupuliferae. 
Frank therefore claims to have established a case of root- 
symbiosis in the Ericaceae, of similar biological significance 
to that assumed for the Mycorhiza of Cupuliferae. The 
epidermis-cells filled with hyphae ‘ constitute the most 
important organ of the whole root, and the sole apparatus 
for the absorption of nutritive materials, and abut in- 
ternally directly on the conducting paths of the root.’ If 
we suppose the cell-walls of the epidermis away, then the 
fungus alone would remain as the medium for conveying 
nutritive substances to the root. 
Enough has been said to show how Frank has gradually 
been led to extend his original idea of a Mycorhiza, so as to 
include not only the type of shortened, thickened, coral-like 
Mycorhiza of the Cupuliferae, but also any root which has 
a fungus mycelium definitely associated with it, in such a way 
