Francis E. Lloyd — 220 — Carnivorous Plants 



to those of U. vulgaris, differing among themselves only as regards non- 

 essential, small details. A description of the trap is deferred till later. 



Freely floating forms. — U. vulgaris itself is the best known and 

 most widely distributed, and will serve well as the type of numerous 

 species, world wide in distribution. 



The plant consists of a cylindrical or laterally compressed axis 

 which may reach a length of 300 cm., probably more, supporting 

 two lateral rows of divided "leaves," and dying off behind as it grows 

 from the tip. The leaves are very crowded toward the growing cir- 

 cinate end. The whole plant is lax and lies in the still water in which 

 it grows entangled, one plant with another, forming often dense mats. 

 Toward the end of the growing season the more terminal internodes 

 become very short and the leaves densely packed to form a resting 

 bud (turion), which sinks or floats, according to circumstances, and 

 may be frozen in the ice. In spring the tips of the leaves or the 

 chief axis proliferate, giving rise directly to new plants with leaves of 

 simpler structure at first. 



A leaf arises from a single lateral outgrowth from the prostrate 

 stem, remaining single in U. oligosperma, or forking as it develops 

 (Pringsheim, Goebel) to form two lobes {21 — 8), at whose bases 

 may arise secondary outgrowths, one on each of which can develop into 

 additional lobes. The third and fourth lobes are not at all or only 

 weakly developed in some species {U. vulgaris) but are strongly de- 

 veloped in others, e.g. U. Thonningii. In others fifth and sixth small 

 lobes are formed laterally to the third and fourth, and are known as 

 auricles. In U. Thonningii (Angola) the auricle is a fan shaped pro- 

 duction, with many rays from its edge, all armed with stiff bristles, 

 occasionally bearing a trap. In U. stellaris (Asia, Africa) and flexuosa 

 (Singapore) the auricles are deeply subdivided, the divisions more 

 or less curved and crowded upon each other. Each leaf lobe is pin- 

 natifid, the pinnae being, however, alternate, the internodes so 

 placed as to produce a zigzag axis, appearing monopodial {20 — i). 

 The lateral divisions (pinnae) have the same disposition of parts. 

 The ends of the divisions are usually armed with stiff bristles, either 

 singly or in bundles, and these afford a taxonomic character. 



The traps are borne on the leaves in such position as to suggest 

 that each represents a leaf division (Goebel, Meierhofer). The 

 details of the structure of the trap will be given fully beyond. Here 

 is only to point out that the trap is always placed with its sagittal 

 section transverse to the plane of the leaf, the mouth facing the 

 apex of the shoot {20 — i). The interior surface of the trap is mor- 

 phologically the upper surface of the leaf division which it repre- 

 sents (hypopeltate, Goebel). In some species only one lobe of a 

 leaf produces traps, the other (upper) half being wholly photosynthetic 

 in function. 



In certain species leaves of a highly speciahzed kind occur on 

 the basal part of the flower stalk. In these the midrib is much in- 

 flated by the enlargement of intercellular spaces while the lateral 

 divisions are much reduced. These are disposed in a whorl ("false 

 whorl") and act as floats to support the inflorescence above the 

 water surface {U. radiata, U. inflata, U. stellaris) {20 — 12). The 



