284 GLANDULAR HAIRa [Chap. XV. 



protoplasm; a still stronijer solution prevents the protoplasm from 

 aggregating into the ordinary full-sized globular masses, and these, 

 though they do not disintegrate, become granular and opaque. In 

 nearly the same manner, too, hot water and certain solutions (for 

 instance, of the salts of soda and potash) cause at first an im- 

 perfect kind ot aggregation in the cells of Drosera; the little 

 masses afterwards breaking up into granular or pulpy brown mat- 

 ter. All the foregoing experiments were made on flower-stems, but 

 a piece of a leaf was immersed for 30 m. in a strong solution of the 

 carbonate (one part to 109 of water), and little globular masses 

 of matter appeared in all the glands, which before contained only 

 limpid fluid. 



I made also several experiments on the action of the vapour of 

 the carbonate on the glands; but will give only a few cases. The 

 cut end of the footstalk of a young leaf was protected with sealing- 

 wax, and was then placed under a small bell-glass, with a large 

 pinch of the carbonate. After 10 m. the glands showed a con- 

 siderable degree of aggregation, and the protoplasm lining the cells 

 of the pedicels was a little separated from the walls. Another leaf 

 was left for 50 m. with the same result, excepting that the hairs 

 became throughout their whole length of a brownish colour. In 

 a third leaf, which was exposed for 1 hr. 50 m., there was much 

 aggregated matter in the glands; and some of the masses showed 

 signs of breaking up into brown granular matter. This leaf was 

 again placed in the vapour, so that it was exposed altogether for 5 

 hrs. 30 m. ; and now, though I examined a large number of glands, 

 aggregated masses were found in only two or three; in all the 

 others, the masses, which before had been globular, were con- 

 verted into brown, opaque, granular matter. We thus see that 

 exposure to the vapour for a considerable time produces the same 

 eflfects as long immersion in a strong solution. In both cases there 

 could hardly be a doubt that the salt had been absorbed chiefly or 

 exclusively by the glands. 



On another occasion bits of damp fibrin, drops of a weak in- 

 fusion of raw meat and water, were left for 24 hrs. on some leaves; 

 the hairs were then examined, but to my surprise differed in no re- 

 spect from others which had not been touched by these fluids, 

 ^lost of the cells, however, inelude<l hyaline, motionless little 

 spheres, which did not seem to consist of protoplasm, but, I suppose, 

 of some balsam or essential oil. 



Pelnrffonium zoiialc (var. edged with white). The leaves are 

 clothed with numerous multicellular hairs; some simply pointetl; 

 others bearing glandular heads, and differing much in length. The 

 glands on a piece of leaf were examined and found to contain only 

 a limpid fluid; most of the water was removed from beneath the 

 covering glass and a minute drop of one part of carbonate of 

 ammonia to 146 of water was added ; so that an extremely small 

 dose was given. After an interval of only 3 m. there were signs 

 of aggregation within the glands of the shorter hairs; and after 

 5 m. many small globules of a pale brown tint appeared in all of 

 them; similar globules, but larger, being found in the large glands 



