204 ANNUAL REPORT 



This rolling inwards or backwards of the margin is slow, and 

 consequently not easily perceived. But we have other plants^ 

 which act more rapidly, forming the second group of the carni- 

 vorous plants under consideration. 



Best known are the species of Sundew or Drosera (Fig. 10),. 

 which grow upon a similar soil as the Pinguicula, and frequently 

 side by side. About forty species of Sundew are known; all are 

 recognizable by the soft, reddish and club-shaped tentacles of 

 their leaves, usually glistening with a drop of moisture. These 

 tentacles start from the upper surface of the leaf, the lower one 

 being smooth, usually resting upon the surface of the soil. All the 

 leaves of this little plant surround the base of the flower-stem, 

 and this similarity of growth with other insectivorous plants,, 

 such as Pinguicula,, Sarracenia, Heliamplioni, Gephalotus^ Bioncea. 

 etc., is very peculiar. A leaf of the Sundew looks like an oval 

 cushion with pins stuck into it. The tentacles are of unequal 

 length, those standing erect in the middle are shortest, largest 

 those near the margin (Fig. 10). About two hundred tentacles- 

 are found upon each leaf, and their knob-like ends are glands. 

 Each gland secretes a clear and sticky fluid, which glistens in 

 the sun like a drop of dew, giving the popular name "Sundew"" 

 to the plants. Vibrations by wind or rain do not produce any 

 change of position in these tentacles; if we purposely put pieces 

 of soil, grains of sand, glass, coal, gum, sugar, starch, tea, or 

 other substances free of nitrogenous matter upon the leaf, more 

 fluid is secreted, which also becomes acid, but no secretion of 

 pepsine takes place, nor any change in the direction of the ten- 

 tacles. But as soon as a small insect, mistaking the glistening 

 pearl for a drop of honey or water, settles upon the leaf and 

 thus touches the glands, or if we purposely drop upon it bits of 

 meat, or the white of an egg, a liberal secretion of acid and 

 pepsine takes place at once. The insect, glued to the plant, is 

 soon covered with the secretion, and dies by suffocation as soon 

 as its stigmata are closed with it. We see that both Finguicula 

 and Brosera act exactly alike, but the latter plant is distinguished 

 by the movements which the tentacles perform. These are 

 best seen near the margin of the leaf. Soon after an insect has- 

 touched some of the tentacles they become excited. The first 

 tentacle coming in contact with the insect bends inwards, mak- 

 ing a movement like the hands of a clock; it moves in two ta 

 three minutes through ^n arc of 45°, in ten minutes of 90°. 

 About ten minutes later the neighboring tentacles move like- 



