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of the tube being rendered germ-tight by a cotton-wool filter. 
The whole apparatus is, of course, previously sterilised by heat, 
and is so arranged that air may either be allowed merely to 
diffuse slowly in and out of the tube through the cotton-wool 
filter, or a supply of moist air, deprived of germs, be slowly and 
steadily drawn through the whole apparatus by means of an 
aspirator. 
The “seed” soon germinates, and if the tube is properly ex- 
posed to suitable light, temperature, &c., the resulting seedling 
—a pure culture of the host-plant—will go on growing and un- 
folding new leaves for several weeks. | Now I have recently 
succeeded in showing that if such a seedling is infected with a 
Uredine, normally parasitic on it, spore pustules of the latter re- 
sult in due course, and if some of these spores be carefully removed 
from such a pustule and transferred to a second pure seedling 
of the grass, we have a pure culture of both host and parasite. 
For, although in the first infection a foreign spore or two may 
have been conveyed to the seedling, because we have at the 
outset to take our spores from an infected plant in the open, it 1s 
extremely unlikely that any contamination occurs in the second 
transference. At any rate, it is found in practice that very valu- 
able results bearing on certain vexed questions of infection can 
be attacked by this method from new points of view. 
As will readily be seen the method can also be employed 
with seedlings of Cress, Beech, Capsella, as well as various 
grasses and other plants, and infections of Pythium, 
Phytophthora, Cystopus, various Ustilagineaw and so forth, and 
I do not despair of extending it even to cases of perennial plants 
and to other parasitic fungi. 
Here, however, it is time to bring to an end this sketch, and 
I have only to say in conclusion that it is in the application ot 
the method and not in the apparatus that success lies. | Methods 
are means, not ends, and to further point the moral we might 
travesty an old saying and declare that—It is men and _ not 
methods that are wanted. 

