354 GLANDULAR HAIRS. CHAP. XV. 



The aggregating process spreads from the glands 

 down the pedicels of the hairs ; and we may assume 

 that any matter which is absorbed ultimately reaches 

 the tissues of the plant. On the other hand, the process 

 travels up the hairs whenever a surface is cut and ex- 

 posed to a solution of the carbonate of ammonia. 



The glands on the flower -stalks and leaves of 

 Primula sinensis quickly absorb a solution of the 

 carbonate of ammonia, and the protoplasm which they 

 contain becomes aggregated. The process was seen 

 in some cases to travel from the glands into the upper 

 cells of the pedicels. Exposure for 10 in. to the 

 vapour of this salt likewise induced aggregation. 

 When leaves were left from 6 hrs. to 7 hrs. in a strong 

 solution, or were long exposed to the vapour, the little- 

 masses of protoplasm became disintegrated, brown, and 

 granular, and were apparently killed. An infusion of 

 raw meat produced no eifect on the glands. 



The limpid contents of the glands of Pelargonium 

 zonale became cloudy and granular in from 3 in. to 5 m. 

 when they were immersed in a weak solution of the car- 

 bonate of ammonia ; and in the course of 1 hr. gran ules 

 appeared in the upper cells of the pedicels. As the 

 aggregated masses slowly changed their forms, and as 

 they suffered disintegration when left for a consider- 

 able time in a strong solution, there can be little doubt 

 that they consisted of protoplasm. It is doubtful 

 whether an infusion of raw meat produced any effect. 



The glandular hairs of ordinary plants have gene- 

 rally been considered by physiologists to serve only 

 as secreting or excreting organs, but we now know that 

 they have the power, at least in some cases, of absorbing 

 both a solution and the vapour of ammonia. As rain- 

 water contains a small percentage of ammonia, and the 

 atmosphere a minute quantity of the carbonate, this 



