NOTES ON PONDWEEDS. 275 



its early summer-state onwards. This latter plant was cut down just 

 as it came into flower in July, when the drain in which it grew was 

 cleared of weeds ; I gathered the second growth in August, again 

 cutting it over to the base, and I found by September it had again 

 sprung up, producing shoots exactly like those gathered in Surrey 

 by Mr. Beeby. I submitted examples to him with the suggestion 

 that his doubtful plant was probably P. Jiuitans. After a careful 

 examination of the two sets of specimens my friend concurred with 

 this view, and determined to admit the species in his forthcoming 

 'Flora of Surrey;' a decision which subsequent observations have 

 amply justified. 



In this autumnal state the leaves are all narrowly linear, 

 elongate, and acutely pointed ; many of them are so closely folded 

 as to look like phyllodes, but they are really exceedingly delicate 

 grass-like leaves, with the lamina distinctly developed. Further 

 observations made on the growing plant in the present summer 

 show that these grass-like leaves are the normal later growth of 

 -P. fluitans, and regularly spring from the axils of the lower 

 stipules when the flowering season is past. Similar shoots, but 

 with much shorter leaves, are also produced in the axils of the 

 upper stipules, when branches are severed from the parent plant by 

 accident, or by natural decay of the lower part of the stem. The 

 severed portion of the branch floats on the surface, and in the 

 course of a few days a fascicle of these narrow leaves springs from 

 each joint as the older leaves decay ; after a little time rootlets are 

 formed at the base of the new growth, which then falls away from 

 the rotten branch, and ultimately sinks to the bottom to continue 

 the life of the species. 



These little fascicles of linear-leaves are analogous to the 



obtusifoli 



fl 



— ■** iuiixio. Alien- uevtuopmeiio in *- 



by the attacks of the larvae of Hydrot r „ r „ . . 



the beginning of August often entirely devour the floating leaves. 

 The largest plant in my pond, measuring 4 to 5 yds. across, is at 

 this time reduced to a mere skeleton by these lame, and the young 

 fascicles of " winter-buds " are rapidly starting into growth, so that 

 m a few weeks there will be thousands of young plants ready to 

 begin an independent existence. The distribution of the wmter- 

 buds of aquatic plants and animals in stagnant waters is greatly 

 assisted by the various species of thread-like Algre winch form tlie 

 ''green- scum" (flannel-weed of fenland speech) that grows so 

 f «ely in p0 nds and ditches. These Algae seem to begin their 

 growth on the very surface of the mud, and as they increase they 

 expand and till the water with a green cloud-like film, which as it 

 nses lifts up from the bottom vast numbers of mollusca and aquatic 

 animals, and also the seeds and winter-buds of aquatic plants, as 

 the thickly- tenanted mass reaches the surface its growth becomes 

 vesicular, and so buoyant as to be easily driven by the wind, as 

 the "rising of the scum" usually precedes stormy weather, its 



In 



distances 



ire thus conveyed for 



t2 



