WEEDS OF PONDS, RIVERS, DITCHES 327 



it as a pest. The typical form (Fig. 92) has delicate 

 submerged round stems ; the leaves are opposite ; those 

 under water are narrow and linear, others, which float 

 on the surface, being broader, generally spathulate, and 

 arranged in the form of a characteristic rosette. The 

 flowers are very small, 

 unisexual, the males with 

 a single stamen, the fe- 

 males with two whitish 

 bracts and a four-celled 

 ovary. 



C. autumnalis L. is a 

 species with dark green 

 submerged leaves only. 



Water Milfoil (Myrio- 

 phyllum alterniflorum DC.) 

 is a frequent pest in 

 lakes, ponds, and ditches, 

 especially in hilly dis- 

 tricts. It has a creeping 

 rootstock, and long, thin 

 floating submerged stems 

 which bearwhorlsof very 

 finely divided leaves. 



The sexual organs are 

 usually separated in dif- 



r i, 'ii FIG. 93. Water Milfoil (Myriophyllum 



ferent small, axillary 3 ver ticiiiat u mi.\ x|. ' 



white flowers. 



In speaking of the damage by water-weeds to boat- 

 ing and angling in the Scotch lakes, Sir Herbert 

 Maxwell says * he would prefer to contend with the 

 troublesome pest Elodea (see p. 332) than with Myrio- 

 phyllum. The latter is " rampant every year " after mid- 

 summer; Elodea only once in six or seven seasons. 



1 Scotsman, Oct. 7, 1897. 



