192 ANNUAL REPORT 



One class is composed of plants which possess cavities into which 

 animals can enter, but which they can not leave again. (See 

 Figs. 1, 4, 5, 6, 8 and 9). No organs to catch and digest are vis- 

 ible, and the plants are thus separated from the second class, in 

 which movements take place as soon as an animal comes in con- 

 tact with certain parts of the plant, and which serve the pur- 

 pose of covering the prey with a digestive fluid. (See Figs. 10, 

 11, 12, 13.) In a third class we have neither cavities, nor 

 any movements performed, but the leaves and other parts of the 

 plant are covered with a glue to hold the animals for digestion. 

 (See Fig. 14.) 



In the first group of the first class we have the plants of the 

 genus JJtricularia or Bladder-wort (Figs. 1 and 2). The traps 

 (Fig. 2) are formed by little bladders, whose mouth is closed by a 

 valve, which allows an entrance, but not an exit of the prisoner. 

 Bladder-worts are plants without roots, which float under water, 

 high or low, according to the seasons. With approach of winter, 

 and the consequent lack of food, the leaves of these plants form 

 upon the end of the floating stem globular winter buds; the older 

 parts of the plant die, the bladders fill with water, and thus be- 

 coming heavy sink the j)lants to the bottom of the pool or pond. 

 Toward spring the buds grow, separate from the older stems, and 

 ascend to the upper layers of the water, where the animal life is 

 already in full activity. Here they soon expand and produce 

 branches, either uniformly covered with leaves, or only in part 

 with leaves and bladders. The ellipsoidal bladders (Fig. 2) are 

 fastened upon stems; their size varies in the different species 

 from two to five millimetres. They are always-pale green, translu- 

 cent, compressed from the sides, with a strongly arched back and 

 less strongly arched bottom. The opening or mouth, which leads to 

 the interior, is always surrounded with ijeculiar stiff and pointed 

 bristles; it is edged by lips, of which the lower one is consider- 

 ably thickened. From the upper lip starts a thin, transparent, 

 slanting valve, looking like a curtain; this valve is quite elastic, 

 and can be readily pushed inward from the outside, so that an 

 animal pressing against it has not the slightest difficulty in en- 

 tering the interior. But as soon as it has entered, and the pres- 

 sure against the valve has ceased, it is a prisoner for life, as the 

 valve, closed by its elasticity as by a spring, can not be opened 

 from the inside. Animals caught make many efforts to escape, 

 but in vain; they die in a short time, mostly within twenty-four 

 hours, though a few can endure their captivity as long as from 



