264 Minnesota Plant Life. 



found growing luxuriantly in great beds almost to the exclu- 

 sion of other vegetation. 



Floating-hearts, The floating-heart is an odd little water 

 plant with a rootstock that creeps in the mud at the bottom 

 of ponds. There are two sorts of leaves. Those which are 

 submerged are grass-like and clustered around the base of the 

 stems, which are thread-like and sometimes ten feet in length. 

 At the surface of the water there is borne a single broadly heart- 

 shaped floating leaf, a little umbel of yellow flowers, and a clus- 

 ter of curious tubers. No other plant in the Minnesota flora is 

 anything like the floating-heart in appearance. The grouping 

 of a bunch of tubers, an umbel of yellow flowers, and a single, 

 broad heart-shaped floating leaf at the end of a slender stem aris- 

 ing from the bottom of a pond will serve at once to designate it. 



Dogbanes. Three species of dogbanes exist in the state. 

 One of them is known as Indian hemp. All of them have 

 a milky juice, so that they are often mistaken for milkweeds. 

 They may be recognized, however, by their flowers, which are 

 somewhat bell-shaped and do not ha\-e the five singular, horn- 

 like appendages of the petals distinctive of most milkweed- 

 flowers, and connected with the remarkable pollination-con- 

 trivance of that family of plants. One of the dogbanes — more 

 abundant in the northern part of the state — has a spread- 

 ing, generally forked stem, with opposite broad leaves, and, 

 in loose terminal cymes, white flowers which mature slender 

 cylindrical pods. In these are enclosed a large number of seeds 

 with tufted flying-hairs at their ends. The Indian hemp sends 

 up erect branches, but not broadly forked at the summit like 

 those of the spreading dogbanes. The flowers are produced 

 in rather thick clusters at the apex, or arise from the axils of 

 the leaves, v^till another variety of dogbane, with clasping 

 leaves, occurs in the southern part of the state. 



Milkweeds. Tlie milkweeds form a family of plants with pods 

 and seeds like those of the dogbanes, but with most extraordi- 

 nary flowers, gathered in most instances in umbels, and fitted for 

 ])o]lination by insects. These are captured by the flowers, as if 

 in a trap, after which ])ollen masses shaped like the old-fashioned 

 saddle-bags are attached to their legs. In Minnesota there are a 

 dozen species of r-trdinavN- milkweeds and fi\'c green nnlkweeds. 



