Physiology of the Genus C us cut a . 83 
defence they were forced to provide some means of elaborating 
organic substance for themselves. 
It is interesting to note also in this connexion that when 
plants of Cuscuta have, either in nature or in cultivation, 
fastened upon innutritious or deleterious hosts, they become 
green in colour just as the cuttings above described. Let 
branches of C. Epilinum , still attached to the mother-plant 
until they have developed numerous haustoria in the new 
host, be brought into contact with the stems of some Etiphorbia 
of much the same diameter as the stems of Flax. When the 
haustoria have developed well, say in five or more days after 
the contact was made, sever the branches from the parent 
stem. Even before the branches are cut off one can see 
a change of colour, the orange being paler and perhaps tinged 
with green ; but soon after they have been cut off they become 
quite green, and remain so as long as the parasite lives. The 
Dodder does not, however, flourish on a Euphorbia , and after 
growing weakly for a time, becoming thinner and thinner, it 
finally dies, and this generally before it has been able to 
bloom. That the green colour is not altogether, or indeed 
largely, due to severing the branches from their parent stem, 
is shown by the fact that branches still attached, which have 
struck their haustoria into plants of Euphorbia , are always 
weaker than those which have attacked other plants, and also 
differ from them in colour. That the former do not take on 
the same deep shade of green as those which are prevented 
by abscission from drawing any food from the parent is only 
what we should expect, knowing to how great distances and 
how abundantly the food secured by more fortunate and well- 
nourished parts is sent to others less well off. If, instead of 
letting a branch of Dodder wind about a Euphorbia , a Linum 
be used as the new host, abscission of the branch from its 
parent after the haustoria have well penetrated, causes 
absolutely no change in colour, for the new host supplies food 
suitable in quality and quantity. The point of the experi- 
ment with Euphorbia as host lies not all in the abscission of 
the branches, but in the development of chlorophyll because 
G 2 
