286 GLANDULAR HAIRS. [Chap. XV. 



of one part of mrlwnnte of ammonia to 218 of water, but the hairs 

 seenjed very little atreeteti by it, excepting that |)erhap8 the glands 

 were rendered rather more opaque. In the leaf itself, however, the 

 grains of chlorophyll near the cut surfaces had run together, or 

 become aggregated. Nor were the glands on another leaf, after 

 an immersion for 24 hrs. in an infusion of raw meat, in the least 

 affected; but the protoplasm lining the cells of the pedicels had 

 shrunk greatly from the walls. This latter effect may have been 

 due to exosmose, as the infusion was strong. We may therefore 

 conclude that the glands of this plant either have no power of ab- 

 sorption or that the protoplasm which they contain is not acted on 

 by a solution of carbonate of ammonia (and this seems scarcely 

 credible) or by an infusion of meat. 



Nicotiana tabacum. This plant is covered with innumerable 

 hairs of unequal lengths, which catch many minute insects. The 

 pedicels of the hairs are divided by transverse partitions, and the 

 secreting glands are formed of many cells, containing greenish mat- 

 ter with little globules of some substance. Leaves were left in an 

 infusion of raw meat and in water for 20 hrs., but presented no 

 difference. Some of tliese same leaves were then left for above 2 

 hrs. in a solution of carbonate of ammonia, but no effect was pro- 

 duced. I regret that other experiments were not tried with more 

 care, as M. Schloesing has shown * that tobacco plants supplied 

 with the vapour of carbonate of ammonia yield on analysis a 

 greater amount of nitrogen than other plants not thus treated; 

 and, from what we have seen, it is probable that some of the 

 vapour may be absorbed by the glandular hairs. 



Summary of the Observations on Glandular Hairs. 

 From the foregoing observations, few as they are, we see that 

 the glands of two species of Saxifraga, of a Primula and Pe- 

 largonium, have the power of rapid absorption; whereas the 

 glands of an Erica, Mirabilis, and Nicotiana, either have no 

 such power, or the contents of the cells are not affected by 

 the fluids employed, namely a solution of carbonate of am- 

 monia and an infusion of raw meat. As the glands of 

 the Mirabilis contain protoplasm, which did not become 

 aggregated from exposure to the fluids just named, though 

 the contents of the cells in the blade of the leaf were greatly 

 affected by carbonate of ammonia, we may infer that they 

 cannot absorb. We may further infer that the innumerable 

 insects caught by this plant are of no more service to iti than 

 are those which adhere to the deciduous and sticky scales 

 of the leaf-buds of the horse-chestnut. 



The most interesting case for us is that of the two species 



* Compte* rcndns.' June 15. paper In given in the ' Gardener's 

 1874. A good abstract of this Chronicle,' July 11, 1874. 



