206 ANNUAL REPORT 



milligram of carbonate of ammonia, and one 30,000 milligram of 

 phosphate of ammonia were sufficient to produce a motion. All 

 the experiments showed that fluid substances excited more than 

 solid ones, and that bending of the tentacles took place more or 

 less rapidly, in the same proportion, as the substance laid upon 

 them contained more or less nutriment for the plant. 



The communication of an excitement through the protoplasts, 

 in a community as that of a plant of Sundew can be compared 

 with the transmission of an excitement by the nerves towards the 

 brain, or with the transmission of a will to the muscles. The 

 transmission is a progressive movement in the smallest parts of 

 nerves, similar to that of sound, of light, of electricity; but it has- 

 never been possible to make such transmission visible. There- 

 fore it is so much more interesting to observe, with unaided eyes, 

 the material changes which occur in the excited protoplasm of 

 the Sundew, and in the protoi^last transmitting this excitement. 



In each cell we can see the protoplast, forming a thick layer 

 close to the wall, and in a contant flowing motion. It contains- 

 in its interior an uniformly colored purple fluid. If a small 

 piece of meat is laid upon such a cell, the content 'of that 

 cell is at once excited, and the uniformly colored purple fluid 

 is dissolved and transformed into dark, round, club-shaped 

 or worm-like pieces, into cloud-shaped balls, and into an almost 

 colorless fluid. This change spreads from the excited gland 

 downward, from cell to cell, through the tentacle, and so forth 

 in all direction and at the same time with these visible signs of 

 a transmission all those tentacles bend in which the purple- 

 colored fluid underwent a change as just described. If the 

 piece of meat is dissolved and digested, or if the tentacles regain, 

 their former position, we see the dark pieces or ball disappear- 

 ing into the body of the protoplast, and the uniform purple color,, 

 found privious to an excitement, is restored in their place. 



The species of Sundew in the iamilj Droseracew occur over the- 

 whole world. Others of this family belong to the genera Dionwa,. 

 Aldrovandia, Byblis, Roridula and Drosophyllum. Each of these 

 genera contains but one or two species, and each species is very 

 local. But all — like the Sundew — catch insects, and j)ossess the- 

 property of dissolving and digesting them. The most peculiar 

 species are, however, Dioncea and Aldrovandia, which form our 

 third group of carnivorous plants of this class. Their organs for 

 digesting and catching are the most peculiar ones in the vege- 

 table kingdom. 



