The Parasitism of Orthocarpus £urpurascens. 261 



Fig. 2. Orthocarpus purpurascens on 

 Astragalus nuttallianus, March 15 1908. 



connection with the Silene the main 

 root of Orthocarpus was broken 

 up into four relatively large roots, 

 and the laterals were few. 



Whatever may be the cause of 

 the modifications of the root sys- 

 tem of the parasite it is of interest 

 to note that the soil conditions 

 were as uniform as one would find 

 in a single habitat, and that the 

 root systems of the host plants had 

 specific differences which the root 

 system of Orthocarpus in some in- 

 stances at least and to a certain 

 degree reflected. Thus, the root 

 of Astragalus are coarse, and those 

 of Festuca and Eritrichium arc 

 filamentous, or relatively fine, and 

 when the roots of the parasite are 

 attached to the roots of those 

 plants they are coarse or fine, as 

 the case may be 



The parasitic habit is more preva- 

 lent among the flowering plants 

 than a person not especially inter- 

 ested in the subject may at first 

 suppose. Among the families 

 lichest in parasites is the Scrophu- 

 lariaceae in which there are said to 

 be 450 species which are at least 

 partly dependent on other plant? 

 for their food supply. To these 

 must be added Orthocarpus purpur- 

 ascens, and presumably others of 

 the genus, which is a hemiparasite, 

 and, as is shown in this note, is at 

 tached to a rather large number 

 of hosts, both perennials and an 

 nuals 



