157 
The hypothesis is for the present quite satisfactory that the 
cotton rust in this one locality was virulently epidemic this past 
spring (in April (?), May and June), on account of unusually 
favorable weather conditions which must have prevailed at the 
time. After the cool winter, the teleutospores on the enigmatical 
alternate grass host, germinating in the favorable rains and dews 
of April and May, would scatter by means of the prevalent winds 
an abundance of infection over to the cotton. * The restricted 
nature of the epidemic argues either that the infection of the 
grass host carrying the alternate stage must have been itself quite 
restricted or else that the weather conditions in the one locality 
only, in the vicinity of Mission, must have been especially favor- 
able for the spread of the disease. 
It seems quite likely that the rust occurs sporadically every 
season, in perhaps many localities. Records show that it has 
11. Cycas circinalis, presented to the Garden on April 1, by Mr. 
Harold I. Pratt. Photo June 27, 1917. (Neg. 2211.) 
