MacDouGaL: INDUCED AND OCCASIONAL PARASITISM 479 
The instances reported in this and previous papers are of this 
character. The instances cited were found by the examination 
of a small number of species. A comprehensive survey of the 
root habits of any region would doubtless reveal a large number of 
parasitic arrangements of various kinds as yet unknown to us. 
The recent discovery of the parasitism of Krameria by Dr. Cannon 
was made by the use of such methods, and has added a tenth to 
the list of families with parasitic members. 
DESERT BOTANICAL LABORATORY, 
Tucson, Ariz. 
