PLATE 48 
Portion of under surface of a cauliflower leaf showing intumescences due to vapor 
of ammonia. Time, 96 hours. The plant was exposed for 15 minutes at 20° C. to 
the vapor from 0.5 c. c. of aqua ammonia (sp. gr. 0.90) in io}4 cubic feet of air space, 
after which the plants were returned to the hothouse. The exposure was made at 11 
a. m., and where no eruptions have appeared it may be assumed that the stomata were 
closed, particularly as the leaf was young. All of the outgrowths are on the lower 
face of the leaf, which is more abundantly provided with stomata than the upper 
surface, although there are also a great many on the latter. All of the smaller intu¬ 
mescences are still covered by a stoma-bearing epidermis. Exposed on August 28, 
1916. Photographed on September 1. 
