4 THE ORCHID REVIEW. [January, 1918. 
} 
z Eg 
NDER the title ‘‘ Recent developments in the Study of Endophytic 
Mycorhiza,” an interesting summary of the experiments of the late 
M. Noel Bernard with the Root-fungi of Orchids, by Miss M. Chevely Rayner, 
B.Sc., has recently appeared (New Phytol., 1916, pp. 161-175). The 
presence of endophytic fungi in the roots of certain Orchids had been 
described by several authors, but it is pointed out that when Bernard 
undertook his researches no information was available as to the time or 
mode of infection of the Orchid seedling, nor yet of the degree of 
dependence—if any—of the two organisms upon one another, or of the 
systematic position of the fungi concerned. Bernard was aware that great 
difficulty was experienced in germinating the seeds of certain Orchids—a 
source of much loss and inconvenience in this branch of horticulture—and 
he sagaciously assumed that the practical difficulty might have to do with 
a critical stage in infection by the appropriate fungus. He thus 
summarised the chief objects of his investigation :— 
1. To germinate seeds of the Orchids under aseptic conditions on 
sterilised media suitable for their culture. 
2. To isolate the root-fungi, grow them in pure culture and identify 
them with certainty. 
3. To compare—for each Orchid species—the behaviour of aseptic 
cultures with those of seeds infected by the endophyte. 
By using seeds removed aseptically from sterilised capsules and sown 
under aseptic conditions, Bernard demonstrated the impossibility of 
raising uninfected Orchid seedlings, and showed incidentally that infection 
takes place subsequent to seed-sowing. He then proceeded to isolate and 
cultivate the root-fungi from various species of Orchid, and was successful 
where all previous workers had failed. He tested the identity of the fungi 
isolated in this way by the inoculation of sterile seeds, induced successful 
germination of the most refractory species by this means, and so 
demonstrated conclusively the obligate nature of the association. 
In later papers he described the details of infection in various Orchids 
and the germination thereby effected, together with many interesting 
observations showing the delicacy of the physiological adjustment. For 
example, early experiments with Cattleya and Cypripedium showed that 
the fungus for Cattleya was effective in inducing germination of seeds of 
Cypripedium, and vice versa. With species of Phalznopsis, Vanda, and 
Odontoglossum, in which the seeds are notoriously difficult to germinate, 
the relation is more specialised, and each plant species has its specific 
endophytic which alone is effective in causing germination. This specificity 
ROOT-FUNGI OF ORCHIDS. 
