WHAT IS A PLANT ? 83 



cases furnish good examples of digestion by plants. 



There are two more recent discoveries to which we must briefly 

 refer. Mr. Francis Darwin has found, by a series of ingenious 

 experiments, that the protoplasmic filaments protruded from the 

 glandular hairs on the leaf of the Commo7i Teasel '^ are able to 

 absorb nutrient matter from the bodies of insects drowned in the 

 water which lies in the cup formed by the opposite leaves 

 at their base. In young plants, these filaments absorb Ammonia 

 from the rain and dew, a not less interesting discovery made by 

 experiments on Dipsaais pilosus, a Teasel not possessing 

 connate leaves, and therefore unable to entrap insects, as the 

 Dipsacus sylvestris, or Common Teasel, can do. 



The other experiments to which we must direct attention were 

 made by Reiss and Will, of Erlangen,t on Drosera, and by Dr. S. 

 H. Vines, of Cambridge, % on Nepenthes. These observers found 

 in the glands of both these plants a digestive " ferment " soluble 

 in glycerifie, and exert ijig its action only in the presetice of an acid, 

 i.e., a ferment precisely resembling those of the pancreatic and 

 peptic glands of animals, namely " pancreatin " and " pepsin " ; 

 moreover, just as, according to Heidenhain, the animal glands do 

 not directly secrete these ferments, but a ?ieutral body called 

 Zymogen, and only when this is decomposed by acids, are the 

 respective ferments set free in an active state, so Dr. Vines finds 

 in Nepenthes a neutral body resembling Zymogen, the decom- 

 posing of which by acids sets free the digestive ferment. 

 The characteristic odour of pepsin can be detected in the 

 secretion of Drosera, and Prof Boulger tells us that the glands 

 of Nepenthes pitchers, after having absorbed nitrogenous matter, 

 become bright red, a process strikingly akin to the blushing 

 of the walls of the stomach after the action of the peptic glands. 



All these researches show the solution of proteiu; or nutrient 

 matter, by plants, to be a process resembling in minute detail a 

 similar process in the animal economy. 



Thus we see that Cuvier's primary test will not hold good as 

 he states it ; but just as the presence of Cellulose or Chlorophyll 



* " Quarterly Journal of Microscopical Science," 1877, p, 245. 

 + Bot. Zeitung, Oct., 1875, No. 44. 

 X Journ. Lin. Soc. Botany, Vol, XV,, p. 472. 



