Orchid Diseases 293 



Culture of PHALiENOpsis 



These plants require plenty of ventilation, but too 

 much of it should be avoided. Frequent syringing is 

 necessary and the temperature requirements from 70 

 to 75 degrees F. at night and about 90 to 95 degrees 

 during the daytime. 



Culture of Vanda 



These plants require shade after February. They 

 prefer a night temperature of 65 degrees F. and seem 

 to thrive best in baskets near the glass. 



Spot Disease of Orchids 



Cause, mechanical injury. 



Symptoms. This disease is manifested as minute 

 pale spots on the upper side of the leaf. The spots 

 vary considerably in size, arrangement, and num- 

 bers, and may occur on any parts of the foliage irre- 

 spective of age. The trouble may be easily over- 

 looked, due to the light color and the superficial na- 

 ture of the spots. With age, however, the spots 

 may go through the entire tissue of the leaf. The 

 cause of the trouble, as explained by Massee,* is of 

 non-parasitic origin. It is brought about by the 

 presence of minute drops of water on the surface of 

 the leaves during very low temperatures while the 

 roots are too copiously supplied with water. The 



*Mawee, &, Annals of Bot. 9:422-429, 1895. 



