80 
The disease attaeks the young seedlings and generally shows itself 
in from three to live weeks. It is lirst indicated externally by the so- 
called “flagging” of the leaves. The chlorophyll no longer shows the 
dark green color characteristic of perfectly healthy plants, but a lighter 
and yellowish tinge. Upon examining the roots of the plants thus 
affected there are found tubercular outgrowths or excrescences vary¬ 
ing in size, according to age, from those scarcely distinguishable to 
those ten or twelve times the diameter of the normal root. These 
swellings seem to be confined exclusively to roots, never occurring on 
the stem or leaves. 
Under the various names by which the disease is known probably 
many tubercular swellings have been described which bear no relation 
to true club-root. Buckman 7 ,* for example, says: “Every field, 
whether of parsnips, carrots, or turnips, will contain roots affected with 
finger-and-toe,” and claims this to be a reversion to their original wild 
form, but he has evidently given a description of the digitate appear¬ 
ance as distinguished from the smooth unbranched condition of well- 
developed specimens. 
So closely do the characteristics resemble those present on the roots 
of the potato, tomato, and parsnip caused by a nematode that one 
would consider them, from a mere casual examination, to be identical. 
In speaking of these galls Atkinson 3 says: “In external appearance 
the enlargements of the roots of the Crucifer*, which are called club¬ 
foot, very much resemble the root galls. Unless one was pretty cer¬ 
tain of the locality from which the diseased specimens came, it would 
be venturesome to undertake to say whether it was root gall or club¬ 
foot.” 
Another form of tubercular swelling is that found on various speci¬ 
mens of Leguminos* (clover, beans, peas, vetches, etc.) described by 
Ward 32 , Brunchorst 6 , Schindler 28 , Tschirch 3 , Prazmowski 23 , Beijerinck 4 , 
and others. Since there i s coi 1 siderable variation on the roots of different 
species, there might arise some difficulty in distinguishing these from 
club-root. Seignette has recently described swellings probably due to 
variation of temperature. The fact that various forms of excrescences 
on roots are plainly due to widely different causes indicates the neces¬ 
sity of discrimination in order to avoid confusion. 
Careful examination of the outgrowths occurring on the roots and 
rootlets of the genus Brassica show the elongated, fusiform swelling to 
be more characteristic of those occurring on the cabbage (Plate xv, 
Eig. 1), while those on the turnip are round or oval (Plate xv, Fig. 2). 
Extended comparison of diseased turnips and cabbages give no sup¬ 
port to the view of W. G. Smith that the cause of the disease can be 
predicted from the form of the swellings. To the unaided eye these out¬ 
growths, especially in the earlier stages, do not seem to differ either 
-V rp 
Hie numbers given after authorities refer to tlie bibliography at the end of the 
paper. 
