CEPHALOTUS: UTRICULARIA 277 



native species are rare. The genus is distributed cliiefly 

 in the north temperate zones. Pinguicula has a rather poor 

 root system. Its leaves, arranged in a rosette lying flat on 

 the soil, are broadly elliptical with margins upturned, and 

 glisten with a sticky secretion from numerous glandular 

 papillae, some of which are stalked, others almost sessile. 

 The flower stalks, each bearing a single fine violet flower, 

 spring from the middle of the rosette. 



Insects are caught in the viscid secretion ; whether they 

 are attracted by it is not known. The glands are then 

 stimulated to increased secretion and the margins of the 

 leaves roll in markedly. The secretion of the stimulated 

 leaves is acid in reaction, and contains a peptic enzyme. 

 Digestion goes on vigorously. 



Much more remarkable are the conditions in the 

 remaining genera. The many species of Utricularia are 

 chiefly tropical, and in the tropics they show the greatest 

 diversity of habitat, occurring as water, land, and epiphytic 

 plants. The few species that occur in the temperate zones 

 are all aquatics. Such are our native Utricularia vulgaris, 

 U. intermedia, and U. minor, the first and the last being not 

 uncommon plants of moorland pools. The flowering axis 

 rises above the water but appears rarely in this country ; 

 the rest of the plant is submerged. Roots are absent through- 

 out the genus. The vegetative body seems to consist of a 

 number of shoots bearing numerous much-divided leaves. 

 Many of the ultimate segments of these are replaced by the 

 bladders. The bladder is a small (about a tenth of an inch 

 long) oval or pear-shaped structure, attached at one side 

 by a short stalk to the leaf. In Utricularia intermedia and 

 others the bladders are borne on special shoots, while other 

 shoots bear only much-divided leaves. At the pointed end 

 of the bladder is an opening to the interior. This is closed 

 by a valve-like lid, joined to the margin above and partly 

 down the sides, with its free lower edge resting firmly 

 on the thickened rim of the opening. From the outer 

 surface of this valve arise a few long, branched hairs ; 

 on the surface of the bladder beside and above the 



