PLATE 4 
Pith cavity of a stem of Ricinus communis showing proliferations of deep origin due 
to the injection of a mixture of strong ammonia and water (aqua ammonia, sp. gr. 0.90, 
1 part, and distilled water 10 parts). The surface of the pith, as at X , X, is dead. 
The proliferations are from the inner face of the xylem at the bottom of the intemode 
and the needle wound was about 5 cm. above this point. Injected on June 2. Photo¬ 
graphed on July 13, 1916. Time, 41 days. X14. 
(188) 
