BPIPETTES, PARASITJSS AND SAPROPHTTES 407 



as the branch of the host increases in diameter, 

 the woody tissue is piled up about the imbedded 

 stem {S) of the mistletoe (Fig. 427). The para- 

 site is not entirely helpless, 

 however, for it has green 

 leaves and twigs, and is there- 

 by able to elaborate materials 

 taken from the air. 



515. The dodder (Fig. 428) 

 spreads its blanched orange and 

 yellow threads over 

 the weeds in low 

 places, often cov- 

 ering them al- 

 most completely 

 by August or 

 September ; and 

 certain kinds 



smother the clover 

 and flax. They 

 are complete par 

 asites, having no leaf -green with which to help 

 themselves. The dodders are closely allied to the 

 morning-glories (and to the sweet potato!) and 

 are twiners. The seeds fall to the ground and 

 germinate tardily in the spring, a slender root 

 enters the ground, and a very slender top, 

 supported chiefly by the nourishment in the seed, 



Fig. 426. 



American mistletoe growing 

 on a walnut branch. 



Pio. 427. 



Attachment of 



the mistletoe to 



its host. 



