44 WHITE RUST. 



of Capsella bearing the rust, dried or fresh ; the same, 

 together with some young terminal portions of affected 

 branches, preserved in alcohol ; the swollen flowers of 

 radish or Capsella taken when not too young, but still 

 tender and brittle, preserved in alcohol ; freshly gath- 

 ered branches of rusted Capsella, or some which have 

 not been gathered more than twenty-four hours and 

 kept in a moist bell jar; chlor-iodide of zinc; potassic 

 hydrate ; and iodine. 



LABORATORY WORK. 

 GROSS ANATOMY. 



1. The vegetative body of the plant consists of delicate 

 transparent threads, ramifying through the tissues of 

 the host on which it grows, and can not be detected 

 without the aid of the compound microscope. 



2. The sort : in a fresh or dried specimen notice 



a. The white blister-like pustules on the surface of 

 the host, son ; shape and extent. 



b. The thin external membrane, at first entire, then 

 becoming ruptured in the middle. 



c. The white powdery spores, conidia, which drop 

 out upon jarring, if the specimen is dry. 



3. Mount a section from an alcoholic specimen of radish 

 flower containing Cystopus, stain with chlor-iodide of 

 zinc, and notice 



a. The numerous dots scattered through the tissue 

 of the radish, the oospores or resting spores. The 

 staining shows them as red dots lying in a blue or 

 yellow ground tissue. 



