5a. Leaves broadly ovate-cordate ; 'spathe white 



Water Arum, Calla palustris. 

 5b. Leaves more or less sagittate; spathe green 



Arrow Arum, Feltandra yirginica. 



LEMNACEAE, the Duckweed Family 



Minute leafless plants floating on quiet water; flowers exceed- 

 ingly small and seldom seen. 



la. Plant thick, ovoid, less than 2 mm. long; roots none. Two species 

 are reported from Michigan Wolffia spp. 



Ib. Plant flattened, with short roots 2. 



2a. Roots several from each rounded plant 



Duckweed, Spirodela polyrhiza. 

 2b. Root single from each rounded plant Duckweed, Lemna spp. 



Three species are reported from Michigan, of which the com- 

 monest is Lemna minor. 



ERIOCAULACEAE, the Pipewort Family 



Bog or marsh herbs, with small flowers in heads terminating 

 long slender scapes. 



One species in Michigan; leaves linear and basal; flower-stalk 

 5 15 cm. high; flower-heads whitish or lead-color 



Pipewort, Eriocaulon articulatum, 



XYRIDACEAE, the Yellow-eyed Grass Family 



Small herbs with basal leaves and erect flower-stalks bearing a 

 head of perfect yellow flowers, in summer. 



la. Base of plant bulbous-thickened (36 dm. high) 



Yellow-eyed Grass, Xyris flexuosa. 

 Ib. Base of plant not bulbous-thickened (1 3 dm. high) 



Yellow-eyed Grass, Xyris moiitaua. 



COMMELINACEAE, the Spiderwort Family 



Leafy-stemmed herbs; flowers with 3 sepals, 3 petals, and 6 

 stamens, lasting but a single day; petals blue. 



la. Stamens 6; petals all equal (Spiderwort) 2. 

 Ib. Perfect stamens 3, sterile stamens 3; two of the petals larger 

 than the third (3 6 dm. high; summer) 



Day-flower, Commelina Yirginica. 

 2a. Sepals villous (310 dm. high; late spring) 



Spiderwort, Tradescantia virginiana. 



2b. Sepals glabrous, or with a tuft of hairs at the apex (4 10 dm. 

 high; late spring) Spiderwort, Tradescantia reflexa. 



