16 



Wolffiella (Mud-midget, Bog-mat) 



Tiny plants floating just below the water surface in quiet water; 

 frond reduced, hollow, gradually narrowed from base to apex, 6-8 mm 

 long, asymmetrical, linear-attenuate, falcate, or sigmoid, many times 

 longer than wide; fronds occurring singly or cohering at the base and 

 radiating in a stellate manner; flowers rare, consisting of a single 

 pistillate and one staminate flower (with a single stamen) enclosed in a 

 sac-like spathe; fruit a utricle; vegetative reproduction common. 



1. Wolffiella gladiata (Hegelm.) Hegelm. Fig. 5, Map 9 



Known from two locations in acidic waters of eastern Massachu- 

 setts. This species has been included in many manuals under the name 

 W. floridana (J. D. Smith) Thompson but is now treated by Landolt 

 (1980) as W. gladiata. Range extends from Massachusetts west to 

 Wisconsin, Missouri, and Arkansas, south to Florida and Texas. 



Rare and endangered plant list: New England 



Spirodela (Great Duckweed, Duck-meat) 



Small flattened floating plants of standing and slow-moving 

 waters; fronds 5-11-nerved, with 6-18 roots; flowers consisting of 1 

 pistillate and 2 or 3 staminate flowers enclosed by a sac-like spathe; 

 fruit a utricle; vegetative reproducton extensive. 



1. Spirodela polyrhiza (L.) Schleid. Fig. 5, Map 10 



Common in standing and slow-moving water of ditches, ponds, 

 lakes, and rivers throughout New England. Range extends from Prince 

 Edward Island, New England, and southeastern Quebec west to 

 southern British Columbia, south to Florida, Texas, and Mexico. 



alkalinity: mean 43.5 mg/1; range 3.5-111.5 mg/1; (20) 

 pH: mean 7.1; range 5.7-7.9; (20) 



Lemna (Duckw^eed) 



Small flattened floating plants of standing and slow-moving 

 waters; fronds 1-5-nerved, with one root; flowers minute, consisting of 

 two staminate flowers (of a single stamen each) and one pistillate (of a 

 single pistil), enclosed in a sac-like spathe; fruit a utricle; vegetative 

 reproduction extensive. 



