200 REPORT OF THE DEPARTMENT OF BOTANY OF THE 
germinate at about the same time. Apparently, conditions favor- 
able to the germination and growth of alfalfa are also favorable to 
dodder. The dodder seedlings are slender, unbranched threads, 
yellowish toward the tip and lighter colored below. (See Plate 
XVIII.) At first they stand upright, attaining a height of about 
an inch. Frequently, the tip is bent over to one side. If the dod- 
der seedling comes in contact with an alfalfa seedling it twines 
around it and fastens onto it by means of haustoria. Then the 
lower portion of the seedling withers and connection with the soil 
is severed. (See Plate XVIII, fig. 2.) Unless the seedling comes 
in contact with some congenial host plant it lives only a few days. 
It soon becomes decumbent then commences to wither in the lower 
portion. Almost invariably seedlings become brown and shriveled 
at the surface of the soil while their tips are yet turgid and of 
normal yellow color. Dodder seedlings have no roots. Ten seed- 
lings which had reached the limit of their growth and commenced 
to wither gave the following measurements respectively: 16, 17, 
20, 20, 20, 20.5, 20.5, 22.5, 25 and 25 millimeters. On another occa- 
sion a seedling was found which measured 31 mm. in length. The 
writers have observed nothing indicating that dodder seedlings are 
attracted by alfalfa. It seems that contact is brought about purely 
by accident. In the field, the beating of the rain is probably one 
of the most important factors in bringing the dodder seedlings into 
contact with the host plant. As soon as the dodder has established 
itself on the alfalfa plant and begins to draw nourishment from 
it, the dodder threads become much larger in diameter and increase 
in length rapidly. The plant attacked soon stops growing and then 
gradually dies. 
PROPAGATION AND DISSEMINATION. 
Where alfalfa seed is grown, dodder produces seeds which, in 
threshing, became mingled with the alfalfa seed. Through the use 
of such alfalfa seed dodder is disseminated far and wide. It is in 
this way, mainly, that New York alfalfa fields become infested with 
dodder. Impure seed is at the bottom of nearly all of the trouble. 
The original dodder spots increase in size from year to year and 
new spots appear occasionally, but dodder does not spread rapidly 
like most weeds. It may exist for years in one corner of a field 
without showing in other parts of it and it rarely spreads to neigh- 
boring fields. 
One reason why dodder does not spread more rapidly is that :t 
does not commonly produce seed here. In many infested fields no 
