CLIMBING PARASITES. GREEN-LEAVED PARASITES. TOOTHWORT. 



181 



second series chiefly in their lack of chlorophyll. They all live underground on the 

 roots of trees and shrubs, develop deep down in the earth a number of flowerless 

 perennial shoots thickly covered with scales, and, in addition, push up annually into 

 the light temporary axes bearing flowers, which ripen their fruits and die after the 

 fall of the seed. 



As the best known representative of this series, we may take the Toothwort 

 (LathrcBa Squamaria), which is represented in fig. 37, and has been already 



Fig. 37. — Toothwort {Lathra:a Squamaria) witli suckers upon tlie roots of a Poplar. 



described on a previous occasion as an instance of a plant possessing in the 

 seclusion of its curious hollowed scale-leaves a special mechanism for the elimi- 

 nation of water from its system quite supplementary to the normal method of 

 surface transpiration. Formerly, the Toothwort used to be included in the 

 family of Broom -rapes (Orobanchefe) on account of the structure of its capsules, 

 but it is entirely different as regards the form of its seedling. For, whereas the 

 seedling of a Broom-rape is a thread without any trace of cotyledons, as will be seen 

 when we study its development and mode of attachment to the host in the next few 

 pages, that of the Toothwort is clearly differentiated into radicle, cotyledons, and 

 rudimentary stem, corresponding in this respect entirely with the Rhinanthacese. 

 Moreover, the Toothwort resembles Rhinanthacese much more than Broom-rapes in 

 the manner in which it attacks its hosts and withdraws nutriment from them. 



