554 ChandlerUtricularia emarginata , Benj, 
segments and the other half remain unchanged at the base. Various 
transitions are noticeable, all showing that the rhizoids are metamorphosed 
water-shoots (Figs. 17-20). 
As fresh water-shoots are produced on the main stem, every well- 
developed flower-stalk is covered at its base by a cluster of water-shoots 
and rhizoids, possibly for the purpose of giving support and stability to 
a stem itself so much thicker and stronger than one of the frail water-shoots. 
The usual number of shoots at the base of a well-developed flower-stalk 
seems to be between twenty and thirty (Figs. 10, 11). 
Bladders. The position of the first bladder has been observed. In its 
subsequent development it does not differ from that of U. vulgaris. The 
development of this organ is perhaps best watched in the region of the rolled- 
up apex of a water-shoot, where it appears in various stages. It arises as 
a roundish knob on a short stalk. Later, a slit is produced which gradually 
becomes larger until the whole becomes hollow. The bladders of U. emar¬ 
ginata only differ from those of U. vulgaris in the shape of the quadrifid 
processes (Fig. 22). 
Morphology. The internal structure of the water-shoot is simple. 
A transverse section of the main stem (Fig. 21) or of one of the leaves shows 
a structure very similar to that of the floating leaf of Salvinia natans , and 
needs but little comment. The vascular system is weakly developed, and 
consists mainly of spiral vessels in the centre of the strand. These spiral 
vessels were very readily seen on treatment of the shoot with caustic potash, 
especially in the examination of the rhizoid segments, into which subsidiary 
vascular strands run (Fig. 16). 
The internal structure of the flower-stalk (Fig. 14) is more complicated 
than that of the water-shoot. It differs mainly in the reduction of the 
aerenchyma, a feature which might be expected from its aerial nature. 
Though larger in its diameter (1-1*5 mm.) a transverse section of U. emar- 
ginata does not differ much in its essential features from that of the peduncal 
of U. brachiata recently described. 1 
The epidermis is composed of regularly shaped cells slightly concave 
and thickened on their outside walls. Inside the epidermis is a small amount 
of aerenchyma. A ring of large cells forms the endodermis. In the ground- 
tissue the cells are small immediately behind the endodermis, but increase 
in size towards the centre, the cells of the pith being as large, if not larger 
than those of the endodermis. As in U. brachiata , five or six groups of 
vascular tissue are irregularly distributed, sometimes bordering on the pith 
and even in some cases occurring just behind the endodermis. 
1 New Phytologist, April, 1908. U. brachiata , R. H. Compton. 
