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. distinguish ed 



A, a.nd C, the hovnwott (.Ceralothyllum); B, the water mUfoil for the bfPlltv 



(Myriophyllam). A is an old leaf, the upper half nonnaUy -, r ^^'^'^^y 



covered with algEe and silt; the lower half cleaned, save for a atld TTaPTflnpP nf 



closely adherent dwelling-tube of a midge larva in the fork at , . „^ a.'-^^^ ^i- 



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

 apical bud. 



