1883-84.] Edinburgh Naturalists' Field Club. 161 



Insects are induced to visit the honey secretion of the lid and 

 mouth of the pitcher, and are thus led on to the conducting surface. 

 This affords no foothold, and they glide down till they reach the 

 detentive surface. When once amongst the hairs of this part of the 

 pitcher, there is no possibility of returning, their struggles only 

 serving to wedge them deeper and more hrmly. The secretion 

 " wets " an insect much more rapidly than water : but it apparently 

 has no digestive properties, appearing rather to hasten decomposition. 

 The broad whig of the pitcher is also said to be baited with honey, 

 so as to lure insects to their destruction by presenting a pathway 

 from the ground. 



Utricularia. 



The British species of this genus are all aquatic, but some exotic 

 species are terrestrial. The aquatic plants are entirely destitute of 

 roots, and the submerged stem and branches are clothed with leaves, 

 which are dissected up into slender filiform segments ; and on these 

 segments numerous little bladders or ampullaB are developed. The 

 leaves are tipped Avith short straight bristles. The plants float near 

 the surface of the water, above which they send their flowers sup- 

 ported on slender stalks. 



In U. vulgaris the bladders are supported on short footstalks, and 

 are about xV of an inch in length. They are generally filled with 

 water, but sometimes they contain air-lnibbles. At the apex is a 

 small orifice, around which are a numl:)er of hair-like prolongations 

 called antennae. On the inside of this orifice is a small hemispherical 

 valve, which shuts against the rim or collar of the orifice. The 

 valve is elastic, and can lie pushed back Ity a small insect, which 

 thus easily finds admission to the inside of the bladder. When once 

 in, there is no chance of its getting out, for the valve springs l^ack 

 against the collar and completely closes the entrance. All over the 

 interior of the bladder small processes called " quadrifids " are placed. 

 These consist of very short stalks, which spring from angular cells at 

 the junctions of the angles of the larger cells ; and at their apices four 

 arm-like processes are developed, each of Avhich consists of a single 

 cell. In U. vulgaris two of these arms are long and two short, but 

 in U. montana they are all nearly of the same length. The bladders 

 were supposed by some to act as floats ; l)ut as they seldom contain 

 air, it is probable that the plants are floated up l^y the air contained 

 in the intercellular spaces. The real use of the bladder is to capture 

 small insects, which they do in great numbers. As already men- 

 tioned, they enter the bladder by pushing back the valve ; and the 

 free edge of this is so thin, and shuts so closely against the collar, 

 that a Daphnia which Darwin mentions as having inserted one of its 

 antenna3 into the slit was held fast for a whole day. The insects 

 captured are all small water-insects, such as Cyclops, &c. \ and, as in 



