Chapter XIV — 261 — The Utricularia Trap 



going discussion by U. monanthos (p. 256) or alternatively by U. 

 dichotoma (they are much alike). The structure of the entrance 

 mechanism has been described. Beyond this is the form of the trap, 

 with its appendages and glands. 



The appendages, when a full complement is present, consist of a 

 rostrum, upper (dorsal) wings and lower (ventral) wings {34 — i). The 

 rostrum projects forward from the overhang; the upper wings arise 

 one from each side of the trap above the door, and the lower wings 

 extend each from a point near the insertion of the stalk up to the 

 lower angles of the entrance. In the various species one pair or the 

 other of the wings may be either suppressed or greatly enlarged or 

 extended, with great differences in the character of their margins 

 {34> 35)- The rostrum is always present, but may be short or ex- 

 tended, to a maximum in U. tuhidata, and sometimes once branched 

 {U. volubilis) (34 — 6). It will suffice to refer the reader to the figures, 

 made with a minimum of detail, for some grasp of the great variety 

 within this restricted group of purely Australian plants. 



In U. volubilis, which grows anchored in rather deep water, there 

 are three forms of traps {34 — 6). Its runner stolons bear traps in 

 groups of three, and these have wings crenately margined, and the 

 rostrum is short. The shoots bear numerous hgulate leaves and 

 among these, exposed directly to the water, are two kinds of trap, 

 large, reaching a length of five mm. (this species has the largest trap) 

 with rather short cylindrical stalks, so that they stand near the surface 

 of the substrate; and smaller ones (2 mm. or less) on very long leafy 

 stalks, and these stand 4-5 cm. above the substrate. The distinction 

 between the water traps is not a sharp one for there are gradations of 

 size and form, but they are on the whole quite recognizable. The traps 

 in the substrate are similar to those of U. monanthos in that the wings, 

 of which there are two pairs, are not laciniate; the rostrum is short 

 and unbranched. The large water traps have a long, sometimes 

 branched rostrum, and the edge of the shallow overhang bears addi- 

 tional fimbriae more or less branched, while the wings are deeply 

 laciniate. The abundance of fimbriae seems to clutter up the front 

 end of the trap. In the long stalked kinds, the ventral wings are 

 much reduced in size and may or may not have a single thread-like 

 lobe. The dorsal wings are single slender processes, as is also the 

 rostrum, which may be once branched. This trap resembles much that 

 of U. tuhulata, which is a submersed floater. Similar behavior is seen 

 in U. Hookeri, also an anchored submersed plant in which the traps 

 are long stalked {ca. i cm.). It bears traps of various sizes, the largest 

 4 mm. long, to smaller ones 1.5 mm. long. In the large traps the 

 wings are slender and fimbriate, but prominent, and the rostrum single, 

 rather long and straight or curved downwards. In the small traps the 

 ventral wings are represented by low ridges, the slender dorsal wings, 

 and the single rostrum, all very long (34 — 7). 



In the little known floating species U. tuhulata, (j5 — 8) the traps 

 have a very long rostrum and filiform dorsal wings, without branches. 

 The ventral wings are absent. In U. Menziesii, different in habit, 

 being totally buried in wet quartz clay with only the leaf blades and 

 flowers showing, there is complete uniformity of trap structure (55 — 



