30 Transactions British Mycological Society. 
noted this type in 1840 in the extremities of the rootlets of 
Pinus sylvestris although he mistook the hyphae for branched 
intercellular canals surrounding the internal cells such as are 
known to exist in the corky layer of the root cortex in Juniperus 
and Thwa. Rootlets so infected are most frequently coralloid 
in appearance. Gasparini in 1856 noted that such rootlets in 
Castanea and Corylus were surrounded by fungal hyphae. 
The term mycorrhiza was coined by Frank* in 1885 for the 
fungus-roots. Even at that date it was known that in some 
plants the fungus occurred in rhizomes as well as roots (e.g. 
Neottia), and since then many cases have been found for which 
the term is quite a misnomer (e.g. Liverworts). It is a con- 
venient term, however, and it is better to accept it with an 
extended meaning rather than to restrict it to those cases for 
which it is etymologically sound. Frank gave special names to 
the two types mentioned above. He used the term endotrophic 
mycorrhiza for those forms in which the fungus occurred within 
the tissues of the host, and the term ectotrophic mycorrhiza where 
the fungus hyphae surrounded the rootlet as a sheath. These 
are convenient general terms, but it is well to remember that 
the two types are not absolutely distinct, as is seen, for example, 
in Monotropa, which had been well described by Kamienski in 
1883. Mycorrhizas, mainly endotrophic, have been described, 
either as usual, or occasional, in various Liverworts, Mosses, 
Horsetails, Club Mosses, Adder’s Tongues, Ferns, Conifers and 
Flowering Plants: and in Algae apart from Lichens we have 
cases of constant association of fungi and seaweeds, as, for 
example, in Ascophyllum and Pelvetia, which each have their 
attendant Mycosphaerella. The antiquity of such associations 
is seen in the fact that they occur in the fossil plants Rhymnia, 
Hornea and Asteroxylon from the Lower (or Middle) Devonian 
—vascular cryptogams which from their simple structure and 
age are of the greatest theoretical importance. Weiss (1904) 
moreover recorded mycorrhiza in fossil roots from the Lower 
Coal Measures for which he proposed the name Mycorrhizonium, 
and Osborn (1909) found fungus mycelia in the inner cortex of 
Amyelon vadicans, the root of Cordaites. 
ORCHID Roots. 
As we have seen, fungi have been recognised in the roots of 
orchids since 1847. A transverse section of an infected root 
taken just above the root-cap shows the fungus in the cortical 
cells (Fig. 1). The distribution is more or less constant in the 
* A. B. Frank, Ueber die auf Wurzelsymbiose beruhende Ernahrung 
gewisser Baume durch unterirdische Pilze. Ber. d. deutsch. bot. Gesell. 111, 
pp. 128-145 (1885). Lehrbuch der Botanik, Bd. I (1892), p. 264. 
