New YORK AGRICULTURAL EXPERIMENT STATION. 231 
acterized by clusters of rootlets which spring from small knots 
or enlargements on the lateral roots. (Plate XXVII, figs. 1, 3, and 
4.) An examination of the surface of the knots with a hand lens 
reveals certain rounded elevations which are either whitish and 
plistening or else pale yellow and dull. These are pear-shaped, 
gravid female nematodes and they are so thoroughly imbedded in 
the root that they appear to be a part of it. However, with the 
aid of a dissecting needle they may be dislodged readily. Under 
the compound microscope they are seen to contain large numbers 
of eggs or of young larve. (Plate XX VII, figs. 3, 5 and 6.) 
The nematode in question is referable to the species Heterodera 
radicicola (Greeff) Mull. which is a common and often destruc- 
tive root parasite of many kinds of plants.5? In New York, it is 
injurious chiefly to plants grown under glass. We believe this to 
be the first published record of the occurrence of a nematode 
disease of alfalfa in the United States. However, Dr. Ernst Bessey 
of the University of Louisiana informs us that, according to his 
observations, alfalfa in this country is often attacked by nematodes. 
Its occurrence, in Germany has been reported by Frank,§* and in 
Egypt, by Mosseri. 
The root knots or enlargements caused by nematodes are readily 
distinguished from bacterial nodules by the fact that the former 
bear one to several short rootlets each, while the latter are entirely 
free from them. 
DISEASES OF UNKNOWN CAUSE. 
WHITE SPOT. 
In this disease the leaves are thickly covered with light-colored 
spots or areas which give the affected plants a whitish appearance. 
The white spots are irregular in shape, rather definite in outline, 
.5 to 1.5 millimeters across and usually distributed irregularly al- 
though sometimes the distal two-thirds of the leaflet is thickly cov- 
ered with spots while the proximal one-third is almost entirely free 
fron them. The affected plants are scattered here and there 
through the field. It is a common thing to find plants so much 
affected that almost every leaf shows the spots without a trace of 
disease appearing on any of the surrounding plants. 
This disease occurs in alfalfa fields all over the State, but we 
*® Atkinson (1); Stone and Smith (1or). 
meuranke (20), (31) (30,83 23). 
© Mosseri (71). 
