230 REPORT OF THE DEPARTMENT OF BOTANY OF THE 
ously by Noack.8* The writers have observed it in New York, fre- 
quently. 
About April 1, 1907, at Geneva, there were a few days of unsea- 
sonably warm weather during which alfalfa started into growth and 
put out new leaves. Then there came a hard freeze. Some of the 
new leaves were kilied outright. Many others were seemingly unin- 
jured; but an examination of them showed that over large areas 
on the lower surface the epidermis was separated from the paren- 
chyma so that it could be removed readily. Sometimes the loosened 
epidermis was shiny, but more often it was simply a lighter shade 
of green than normal. 
After heavy frosts (28° F.) occurring May 11 and 12, 1907, 
alfalfa showed no material injury on May 13. However, many of 
the leaves were partially wilted, somewhat wrinkled and gray-green, 
with the epidermis on the lower surface plainly separated from the 
parenchyma. In some cases the loosened epidermis was ruptured. 
By May 4, 1908, alfalfa on the Station farm had made a new 
growth about five inches high. Although the plants were not 
materially injured almost every leaf showed large frost blisters 
on the lower surface. The younger leaves were gray-green and 
slightly wilted as a result of the light frosts of May 1 and 4 when 
the minimum temperature was 30° F, in both cases. The older 
leaves were considerably wrinkled and distorted and often showed 
ruptures in the loosened epidermis. Their injury was due probably 
to the hard freeze of April 21 when the temperature went down 
tO. 20" ek 
INSECT ENEMIES. 
The insect enemies of alfalfa have not been included in this in- 
vestigation. All that can be said on the subject is that we have 
seen in New York no instance of serious injury to alfalfa caused by 
insects. 
ROOT-KNOT. 
Alfalfa root-knot disease caused by nematodes is of frequent 
occurrence in New York. This first came to our attention in Au- 
gust, 1907, when a newly-seeded field of alfalfa near Geneva was 
found to be thoroughly infested. Subsequently, the same trouble 
was observed in many fields in various parts of the State. How- 
ever, the damage done by it seems to be small. 
Root-knot is a very appropriate name for the trouble. It is char- 
” Noack (72). 
