ENTOMOLOGICAL NEWS [Oct., 'l8 



days, each seed germinates a small leaf. Upon first issuing 

 forth this is nearly round in shape, about i mm. in diameter, 

 and resembles a tiny green ball. This leaf continues to grow 

 under water until about the third day, when it is usually 3 or 

 4 mm. in diameter. It then slowly rises to the surface of the 

 water and is soon floating buoyantly. A second leaf usually 

 makes its appearance on the first or second day after the young 

 plant has reached the surface. Several slender, threadlike 

 rootlets also make their appearance soon after the surface has 

 been reached, and extend downward in the water. About 

 every five or seven days thereafter a new leaf adds itself to 

 the formation of the rosette. On a i-i-day-old plant of average 

 size the leaves are about 10 mm. long, 8 mm. wide, and the 

 rootlets about 15 mm. in length. The growth is very rapid 

 and in a few months a plant attains a diameter of from 5 to 

 8 inches, and may have several runners, with young sprout 

 plants attached, fastened to it. 



Older and larger specimens may be found having from 16 

 to 20 leaves, some of the latter being from 7 to 10 inches in 

 length. The roots attain a length of y/ 2 feet, and open out 

 sufficiently to form a bulky mass below the surface of the 

 water. 



In new locations these plants grow in great numbers in the 

 quiet water near the shore, where they are protected from the 

 winds and currents. They multiply so rapidly that large 

 masses are soon formed. Strong winds, or heavy rains, 

 causing an elevation of the water, tend to set these floating 

 masses of plants in motion, and they drift about on the sur- 

 face of the w r ater with the action of the winds and currents, 

 until they are again swept into protected coves or lodge be- 

 tween the dead trees in the inundated area. Here the masses 

 continue to enlarge and each day finds a little more of the 

 surface of the water covered with a bright green carpet of 

 Pistia. When we consider that propagation occurs both by 

 seeds and runners, an idea may be formed of the rapidity with 

 which it multiplies. 



During the dry season there is a noticeable difference in the 



