354 GLANDULAR HAIRS. Cuar. 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 m. 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 effect on the glands. 
The limpid contents of the glands of Pelargonium 
zonale became cloudy and granular in from 3 m. to 5m. 
when they were immersed in a weak solution of the car- 
bonate of ammonia; and in the course of 1 hr. granules 
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 
