154 



Aquatic Organisms 



water. Increase is by budding and outgrowth of new 

 lobes from pre-existing thalli. Flowering and seed 

 production are of rare occurrence. 



The water lily 

 family includes 

 the more con- 

 spicuous of the 

 broad- leaved 

 aquatics, which 

 pre-empt the 

 rich bottom mud 

 with stout root 

 stocks, and 

 heavily shade 

 the water with 

 large shield- 

 shaped leaves, 

 either floating 

 upon the sur- 

 face, as in the 

 water shield and 

 water lilies or 

 lifted somewhat 

 above it, as in the 

 spatterdock and 

 the lotus. They 

 are long-lived 

 perennials, re- 

 quiring a rich 

 muck soil to root 

 in. These are 

 FIG. 64. Leaf-whorls. distinguished 



A, and C, the hornwort (CeralophyUum) ; B, the water milfoil foT the beauty 



(Myriophyllum). .4 is an old leaf, the upper half normally 1 r ~ 



covered with algae and silt; the lower half cleaned, save for a and iragranCC OI 



closely adherent dwelling-tube of a midge larva in the fork at , . 



the right. C, is a young partly expanded leaf whorl from the tiieiT 

 apical bud. 



