Hope — The ‘ Sadd 1 of the Upper Nile. 515 
Another case of obstruction by aquatic vegetation in 
America is found in Florida, U. S., North America, where — 
originally introduced from tropical South America for its 
beauty as a flowering plant— the so-called Water Hyacinth has 
become naturalized, and has increased to such an enormous 
extent in the St. John’s River as to cause serious apprehen- 
sion that navigation may be altogether closed. A Report to 
the U. S. Department of Agriculture, Division of Botany, by 
Mr. H. J. Webber, published as Bulletin No. 18 of the De- 
partment (Washington, 1897), gives full information con- 
cerning the vegetation which causes the obstruction, and the 
nature of the damage, of various sorts, caused by it. The 
Water Hyacinth, Eichhornia speciosa , Kunth (syn. E. crassipes 
(Mart.), Solms — Piaropus crassipes (Mart.), Britton), is the 
main factor in the block. It belongs to the Pontaderiacea 
Order. The leaves form a rosette one to two feet high, which 
remains above water as the plant floats ; the basal portions of 
the leaf-stalks of young plants are strongly swollen, but as 
the plant becomes older the swellings gradually disappear, 
and the petiole lengthens. The swellings on the petioles of 
the young leaves act as air-reservoirs, and thus ensure the 
stability of the young in water. Old plants become thoroughly 
entangled, and are in no danger of being overturned. The 
long petioles are full of air. The roots form a dense, bushy 
mass, reaching in many cases a length of over two feet. The 
plant bears spikes of light-blue or violet flowers, and blooms 
freely, and this has led to its being widely cultivated in 
America and Europe. Plants, now coming into flower (July 
1902), may be seen in the tank in the Victoria Regia house 
in the Royal Gardens, Kew. 
The water hyacinth is mostly limited in its growth to 
sluggish fresh-water streams, bayous, lakes, ponds, & c. In 
Florida the plants are generally found lining the shores of 
lakes and rivers in immense numbers. In certain lakes the 
entire shores are lined with a solid mass for fifty to several 
hundred feet wide, and small tributary creeks of the St. John’s 
River are entirely covered. The main channel of the river 
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