66 
Seedling cabbages, which show by the nodular swell- 
ings that they are attacked by Club-Root, are often 
exposed for sale. Of course it is inadvisable to plant 
such seedlings, for not only is it extremely unlikely that 
they will produce healthy plants, but when they decay in 
the ground they will infect the soil. If any plants of the 
cabbage family are grow in the same soil within two or 
three years of this infection, thev will almost certainly 
suffer from the disease to an even greater extent. 
The disease with which we are dealing should not be 
confused with the gall-like swellings on the roots of 
cabbages and turnips, sometimes caused by the larva of a 
beetle that lives within the cavity .of the swollen tissue. 
Eelworms, as well as certain bacteria, are also able to 
produce small swellings on the roots of many plants, in- 
cluding Crucifers. It is a little unfortunate that fequently 
any swellings on roots of cruciferous plants are spoken of 
as Club-Root without reference to the causal organism. 
Since, however, in the vast majority of such cases the slime 
fungus, Plasmodiophora Brassicae, is the cause, I am re- 
stricting the name Club-Root or Fuingers-and-Toes to 
the disease of which it is the cause. Whilst the life history 
of Pythium and of the other fungi mentioned in the last 
chapter is typical the Club-Root fungus differs somewhat 
im life story and mode of nutrition. 
When one of the diseased roots, say of turnip, is cut 
across and examined under a microscope it is found that 
the tissues of the root are altogether abnormal, many of 
the cells being strangely altered. In the healthv root of 
the turnip we can distinguish an outer band of softer 
tissues surrounding a central core containing a certain 
number of woody elements arranged like the spokes of a 
wheel. Between the last-named are broad wedges of 
softer cells which are packed with the reserve food material 
that is stored in the root of the turnip in the form of 
sugar. The root increases in thickness by the growth and 
division of a layer of cells near the outer part of the 
central core. When attacked by the fungus of which we 
‘are speaking, the whole machinery for the growth of the 
root 1s, as it were, thrown out of gear; cells which normally 
would produce woody tissue simplv give rise to giant thin- 
walled cells, and the result is an excessive production of 
thin-walled tissues. This also occurs in the position of 
the tissues which normally serve for the conveyance and 
