Minnesota Plant Life. 



199 



smaller and higher on the stem than the pistillate. The fruit 

 has but a single cavity. The seeds are furnished with con- 

 siderable albumen and within this the embryo stands nearly 

 straight. These plants are sometimes mistaken for sedges, but 

 are easily recognized by their globular flower-heads of two sorts 

 on the same general branch. Sometimes the heads are pro- 

 vided with stalks ; in other varieties they are sessile. 



The second order in the ascending series includes seven fam- 

 ilies, of which five are represented in the Minnesota flora. 



FIG. 77. lyakeside vegetation. Just off shore is a growth of the floating pondweed, then of 

 arrowheads, while further out are reeds and rushes. After photograph by Williams. 



Pondweeds. These are for the most part submerged plants 

 growing in ponds, lakes and slow streams throughout the state. 

 About twenty Minnesota species are known to exist in such 

 localities. They all root at the bottom of the water. Their 

 stems are slender, often branching, and when taken out of the 

 water are limp, owing to their poor development of woody tis- 

 sue. The flowers are commonly collected in spikes which in 

 spring are barely thrust above the water in order that the wind 

 may carry the pollen from the stamens to the stigmas. These 

 spikes are the little objects upon which lake-flies like to perch 



