356 



SCIENCE. 



(Vol. VII., No. 167 



secretion of pepsin. The process is almost pre- 

 cisely like that which occurs in the animal 

 stomach, — a secretion of acids and ferment pro- 

 duced by the contact of digestible substances. The 

 ferment or pepsin is not, however, a peculiarity 

 of such plants alone. The milky sap of many 

 others contains the same substance, and almost 

 generally throughout the vegetable kingdom a 

 ferment is produced in seeds during germination, 

 rendering the reserve material, upon which the 

 young plant is dependent, assimilable. 



Yet better known is another plant of the same 

 family (Droseraceae), the venus fly-trap (Dionaea), 

 that grows in the wet lands of North Carolina. 

 The leaves, about six centimetres in length, spring- 

 ing from the ground, have an elongated, winged 

 stalk, bearing an orbicular leaf at its extremity, 

 which is capable of sudden folding or closure. 

 Along the margin of each leaf are a number of 

 long, immovable, bristly hairs ; and near the mid- 

 dle of each side, on the upper surface, three 

 slender irritable hairs, which have the peculiar 

 power, when touched, of conveying the irritation 

 to the leaf-tissue, and causing immediate closure, 

 the marginal bristles crossing each other, and pre- 

 venting any possibility of escape. In addition 

 to these hairs, there are a large number of glandu- 

 lar bodies attached by a short stem, which not 

 only secrete the digestive fluids, but also serve as 

 absorptive organs for the digested material. An 

 insect or any digestible substance caught by this 

 singular contrivance remains enclosed a relatively 

 long time, while an inorganic or non-digestible 

 object is much sooner released. 



In a very different way the leaves of species of 

 the pitcher -plant (Nepenthes) serve to entrap in- 

 sects. Here the long leaf is prolonged into a ten- 

 dril, which bears at its apex a tubular or oblong 

 pitcher, sometimes a foot or more in length, closed 

 with a hinged lid. About its rim there are a 

 number of nectar-secreting glands, by which in- 

 sects, and especially ants, are attracted. Entering 

 easily into the upper part of the tube, they fall 

 from the smooth surface to the bottom. Here 

 there is a very large number of secreting glands, 

 which, singularly, only in consequence of the irri- 

 tation produced by the insects, pour out a con- 

 siderable quantity of digestive fluid. This secre- 

 tion shows, in the presence of albumen and flesh, 

 a strong acid reaction, which, together with the 

 associated pepsin, acts energetically upon animal 

 substances, digesting them in a short time. 



Again, species of our native Saraoenia have the 

 ascending hollow leaves so enclosed by a lid as to 

 prevent the entrance of rain-water, but, by the 

 nectar glands, attract and entrap insects, which 

 are digested by the abundant secretion at the 



bottom. In addition to these, the aquatic blad- 

 derworts, or Utricularia of Europe and North 

 America, although secreting no digestive fluid, 

 may properly be classed among the insectivorous 

 plants. The small bladders are so closed by a 

 valve as to admit the ingress of insects, crustaceans, 

 or newly hatched fish, but prevent their egress ; 

 and, from the large number that they are fre- 

 quently found to contain, it is very probable that 

 the ensuing decomposition is of direct advantage 

 to the plant in furnishing nutritive, absorbable 

 compounds. 



The question, finally, whether organic material 

 obtained and dissolved by the plant in the ways 

 briefly described is indispensable or serviceable as 

 nutrition, is important. Various carnivorous plants 

 have been cultivated, secluded for a long time 

 from all contact with organic material, without 

 apparent deterioration in their development, so 

 that it may at once be determined that such matter 

 is not indispensable. However, in experiments with 

 plants of Drosera rotundifolia, all kept under pre- 

 cisely the same circumstances, except that some 

 were deprived entirely of organic food-material, 

 while others received insects from time to time, it 

 was found that the latter throve much better, and 

 fructified much more abundantly. 



These views, that the substances are of direct 

 benefit to the plant, are, however, contested by Dr. 

 Behr in a late number of the Pharmaceutische nmd- 

 schau, who claims that it is not proved that the 

 dissolved material is taken up as nutritive material, 

 and so made use of. Its presence within the cells, 

 or in the tissue of the plants, may be explained by 

 simple capillarity, which is further evidenced by 

 the absorption of inorganic substances, such as 

 arsenious acid, by means of the secretions, as has 

 been recently shown by Jaeger. 



This opinion Dr. Behr supports by observations 

 on species of Nepenthes, where he found that the 

 pitchers, after the reception and solution of insects, 

 were in no wise strengthened, but became injured 

 and withered ; and in cases of Drosera sulfurea 

 and rosulata, where he likewise found that the 

 leaves which had captured an insect always 

 withered, and where many leaves were thus robbed 

 of their true function, the plant weakened and 

 died. He mentions the singular fact that the 

 larvae of certain insects (Xanthoptera semicocca) 

 are known to live in the exudations of Saracenia 

 variolaris without being affected by the digestive 

 fluids, — habits very similar to the known ones of 

 bot-flies in the animal stomach. 



It is very difficult indeed to understand how 

 such remarkable contrivances, in connection with 

 true digestive fluids, can exist, save on the theory 

 that, their function is a real one, and that they 



