340 GEORGE MASSEE [NOVEMBER 
black rust—Puccinia graminis. No trace of yellow rust—Puccinia 
glumarum—was present. 
The following season the remaining half-pound of wheat was sown 
under conditions precisely similar to those described above. The 
plants protected by glass globes remained perfectly free from rust of 
any kind, whereas the seed sown on manure, and fully exposed to 
atmospheric conditions, showed at the expiration of thirteen weeks, 
twenty-eight per cent of rusted plants; the rust being Puccinia 
graminis. Not a trace of yellow rust—Puccinia glumarum — was 
present. 
Remembering the clause in Eriksson’s theory that the mycoplasma 
only assumes a visible form “if the conditions are favourable,” I am 
ready to admit that both my out-door and other experiments with 
“ Horsford Pearl” were not grown under the conditions necessary for 
the conversion of mycoplasma into mycelium, nevertheless my experi- 
ments are not unique in this respect. 
McAlpine of Melbourne records having received from Eriksson ten 
varieties of wheat showing in a marked degree powers of resistance to 
yellow rust—Puceinia glumarum. When sown in Australia all the 
varieties were attacked by one or other of the native rusts—Puccinia 
dispersa, or P. graminis. No trace of yellow rust—P. glumarum—was 
observed (8). 
These experiments corroborate at least what has previously been 
stated (9), that cereals especially susceptible to one form of rust in a 
particular country, may, if sown in another country, lose their suscep- 
tibility for the original kind of rust, and prove equally susceptible to 
another form. 
As to whether this also proves that mycoplasma does not in reality 
exist, or that a change of locality destroys a mycoplasma that 
previously existed, I am not at present prepared to say. 
Another set of experiments with wheat, commenced before the 
mycoplasma theory was published, were conducted for the purpose of 
endeavouring to ascertain whether mycelium passed into the seed in 
those cases where the mycelium of a parasitic fungus was undoubtedly 
present in the fruit. 
This line of research was suggested by a remark made by Collenette 
(10), who in writing on the Tomato disease in Guernsey, says :—“ My 
theory, then, is that the ‘sleeping’ disease is really primarily pro- 
pagated by the seed, and the first thing to be done is to refuse to save 
or use the seed derived from the diseased plants.” Collenette’s theory 
was founded on the discovery of delicate hyphae in the tissue of tomato 
seed produced by a diseased tomato. I also had an opportunity of 
examining some seed obtained from a diseased tomato, kindly furnished 
by Mr. Collenette, and succeeded in detecting slender, hyaline hyphae 
about 2m thick in the testa of the seed, but at the time was not able 
to demonstrate that these hyphae were genetically connected with 
