296 Diseases of Greenhouse Crops 



phillipinense. Infection takes place by means of 

 a wound. 



The Organism. Bacillus cypripedii is a medium 

 sized slender rod-shaped organism, rounded at both 

 ends, occurring in chains of 2-3, and motile by 

 means of ilagella. On agar it forms a smooth, light 

 grayish white colony with a pearly luster, and a 

 dirty cream-colored growth on potato plugs. It pro- 

 duces a film on bouillon, coagulates milk, and rap- 

 idly dissolves gelatin. It is not known whether the 

 causal organism is the same or closely related to the 

 one described by Peglion * under the name of Bac- 

 terium oncidii Peg, as causing a disease on orchids. 

 Very little is known of the methods of control. 

 Since infection takes place through a wound, care 

 should be taken to prevent careless washing with a 

 rough sponge. Diseased material should be de- 

 stroyed by fire. 



Rust of Orchids 



Caused by Hemileia oncidii Griff and Maubl. 



Symptoms. The disease is characterized by mi- 

 nute yellowish spots, the surfaces of which become 

 covered with an orange-colored powder which is 

 made up of the spores of the causal organism. The 

 spots enlarge, the center turns brownish, while 

 the advancing margin remains an orange rust color. 

 The disease was first described by Griffon and Mau- 



* Peglion, v., Centralbl. fiir Bakt. 5:33, 1899. 



