Reconquest 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 4o 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? to see how 
distinct is the water type.® 
127 
