Rcconquest of the Water 



One can see also how other peculiarities, which are 

 common to most water plants, have turned out to be 

 useful instead of detrimental. 



There is a general softness and flaccidity about them. 

 Lignin (woody matter) and cork is but little developed. 

 The main stem of the reedgrass, Phragmites, cannot stand 

 erect, but lies lengthwise in the water, giving off its up- 

 right foliage and flowering shoots with their wonderfully 

 contrived leaves and feathery sprays of flowers. " Prone 

 on the flood, extended long and large," such a stem, per- 

 haps 40 to 50 feet long, is of great advantage, for, 

 as we shall see later, this method of growth has been 

 essential to the formation of alluvial meadows (see p. 133). 



The evidence upon the effect of water-life is un- 

 usually complete and satisfactory owing to the researches 

 of Costantin and especially Henslow.* It is not only 

 that there is a vast body of aquatics which agree in 

 the possession of certain characters, but there are such 

 plants as Polygonum amphibium and Ranunculus aqua- 

 tilis which both live on land and thrive in the water. 

 These amphibious species take on sponginess, lose their 

 hairs and most of their woodiness, and alter the char- 

 acter of their leaves promptly when transferred from 

 land to water. 



Wholly drowned leaves, such as those of many forms 

 of pondweed (Potamogeton), and water crow's-foot, 

 water milfoil, and the like, are generally slimy, often finely 

 divided, long drawn out and much branched. The 

 slimy character (due probably to the more mucilaginous 

 character of the cellulose) prevents friction with the 

 water, and in other respects the leaf simply yields itself 

 to the current, and is, so to speak, " combed out " by it. 



* Costantin, Henslow. The adverse criticism of Freidenfeldt is not clearly 

 expressed, for one has only to compare the types given by Bonnier 2 to see how 

 distinct is the water type. 3 



127 



