200 THE ORCHID REVIEW. [Juty, 1922. 
“There are other phases of the problem presented by Bernard, 
especially the loss by the fungus of its capacity to induce germination after 
prolonged culture in the laboratory. It is entirely possible that there has 
been no loss in the fungus, but that at.the time of inoculating the culture 
the physiological state of the embryos was such as to resist or permit of 
infection. Those in which the infection was confined to the lower cell 
could still germinate despite the fungus. Those invaded to a greater extent 
would be killed. These and and other experiments of Bernard and Burgeff 
suggest that one of the causes for the failure of germination is the parasitic 
character of the fungus. In other words, it is possible that the fungus, 
instead of being an aid in normal germination, is a factor in the death of 
the embryos, and consequently in the failure of germination.” 
It is stated finally that ‘‘the evidence for the necessity of the fungus 
for germination has not yet been conclusively proved. The evidence is 
conclusive that under conditions of pure culture employed by both Bernard 
and Burgeff germination of the seeds is dependent on the fungus.”” 2To many 
it will seem, as it does to the writer, that conclusive evidence in the one 
case would be equally conclusive in the other. What is the evidence 
upon which the usual theory is based? Whatever may be the theoretical 
explanation—and on this aspect experiments are still in progress—there 
are certain incontrovertible facts. 
1. The roots of all Orchids growing naturally have fungus mycelium 
in their cortical cells. (Hundreds of species have been examined, and in 
every case, except that of the saprophytic Wuhlschlagelia aphylla, fungi | 
have been recorded. Under cultural conditions fungi are sometimes absent). 
When these fungi are isolated and grown in culture, they can be arranged 
in certain groups or species—an ‘‘ Odontoglossum fungus,” for example, has _ 
a totally different facies from a “ Cattleya fungus.” 
2. The fungus present in Orchid roots is always the same genus 1.€.— 
Rhizoctonia of Bernard, Orcheomyces of Burgeff. The only known case 
where a different genus is concerned, is the Japanese species, Gastrodia 
elata, where the toadstool Armillaria mellea forms an association with the 
tuber. (The details of germination in this species are not yet’ known). 
3. When seeds of Odontoglossum, for example, are sown on a series. 
of root-fungus cultures, there is no germination in some cases, in others 
germination is very poor, while in others apparently every seed germinates, 
the mycelium spreading over the glass stimulates seeds which may happen 
to be there, and these frequently reach the stage of producing leaves. The 
fungus which brings about this last type of germination where, in a normal 
flask, the whole surface is covered with a green mat of germinating seeds, is 
the fungus isolated from the roots of the parent plant ? Any other fungus than an 
Orchid fungus, if it enters the seed, acts as a parasite and kills the seed. 
