90 West . — On Stigeosporium Marattiacearum and 
was sterilized by immersion for varying short periods in very dilute solutions 
of formalin, mercuric chloride, or hydrogen peroxide, followed by thorough 
washing in running water. Failing this preliminary superficial sterilization 
of the host-root, a number of forms appeared in the cultures. The numerous 
genera represented in such cultures obviously constitute the epiphytic 
mycoflora of the roots in question and have no necessary connexion with the 
mycorrhizal fungus. 
Bearing these results in mind, it is only reasonable to suppose that the 
fungal growths which Kuhn (28, p. 493, Taf. XX, Fig. 40) succeeded in 
isolating from roots of Marattia alata , Sm., were of a similar nature, for 
they were obtained from roots which apparently had not been previously 
sterilized. 
In this connexion it is interesting to find that Gallaud (1. c.) invariably 
failed to obtain cultures of the numerous mycorrhizal fungi which were inves- 
tigated by him. This observer suggests that the mycelium of the endophyte 
undergoes some vital change during its sojourn within the tissues of the 
host-plant. The present writer is of the opinion that Gallaud’s explanation 
is correct. 
Noel Bernard (1, 3, 4, 5, 6, 7, 8, 9), however, in the course of a series 
of cultural experiments extending over a number of years, succeeded in 
isolating a number of mycorrhizal fungi from the roots of various genera of 
Orchidaceae and brought to light the remarkable degree of specialization 
which obtains in these plants. This botanist proved that the germination 
of the seeds of certain Orchids and the subsequent development of the root- 
system of the seedlings depended upon their association with their particular 
fungal symbiont, and in this way solved the problem which in the past had 
puzzled Orchid growers, namely, the apparent impossibility of raising 
certain genera of Orchidaceae from seed. 
An ingenious theory that tuberization in a number of higher plants 
depended upon their infection with a fungal endophyte, which brought about 
an increase in the concentration of the cell-sap, was advanced by this 
observer (2, 9, 10). Many of these experiments were afterwards repeated 
and confirmed by Burgeff (11). 
Rayner (1. c., p. 1 30) succeeded in isolating an endotrophic fungus from 
seeds and from pieces of ovary tissue of Calluna vidgaris and in effecting the 
synthesis of sterile seedlings of the higher plant with this fungus, thereby 
inducing development of the root-system and vigorous growth under 
aseptic conditions in closed tubes. 
There is good reason to believe that the only parts of our fungus 
capable of an independent existence outside the tissues of the host are the 
resting spores and germ-hyphae ; hence it was unfortunate that in the only 
living material available for investigation the vegetative structures of the 
endophyte were alone represented. On this account no experimental work 
