MACLOSKIE: LEMNACE^E. 291 



inson, of the Gray Herbarium, for identification by Professor C. H. Thomp- 

 son, Missouri Botanic Garden. (See also Thompson in Report of Missouri 

 Bot. Gard. 1897.) It occurs also in British Guiana. 



2. LEMNA Linn. Duckweed. 



Frond disk-shaped, with a central nerve, and sometimes also with 2-4 

 lateral nerves ; with one rootlet usually ending in a blunt rootcap. Fruit 

 ovoid, ribbed. 



Species 7, in temp, and trop. regions. (Fig. in Brit. & Br. i, 366.) 

 Hatcher info'rms us that "Duckweed is abundant in the waters" of S. 

 Patagonia. 



1. L. GIBBA Linn. 



Frond unsymmetrical, minute, thickish or gibbous underneath, -3-5- 

 nerved. Ovules 2-6, anatropous ; seeds deeply and unequally ribbed. 

 Cosmopolitan ; in quiet waters of Chili ; probably also in Patagon. 



2. L. MINOR Linn. 



Frond thickish, obovate or orbicular, sometimes purplish, with 3-5 

 lateral nerves. Ovule i, orthotropous ; seed i2-i5-ribbed. 

 Distribution as the preceding ; in pools near Rio Chubut. 



3- L. VALDIVIANA Phil. 



Frond oblong-elliptical, thin, short-stalked, nerveless. Seed 2O-ribbed. 

 (N. and S. Amer., Chili) ; Argentina. 



3. WOLFFIELLA Hegelmaier. 



(C. H. Thompson in Missouri Bot. Gard., 9th Annual Report, 1897.) 

 Wolffia and Wolffiella agree in being rootless, nerveless, leafless, with 

 a terminal reproductive pouch, from which arise sessile branches which 

 soon become separate fronds. The fronds of Wolffia proper are sub- 

 globular ; those of Wolffiella are elongated, very thin and punctate, with 

 brown pigment-cells. Flowers and fruit of Wolffiella are unknown. 

 Species 4, warm parts of Amer. 



W. GLADIATA Hglm. 



Frond about 6 times as long as broad, widest at the deeply excavated 

 reproductive pouch. (Fig. in Eng. & Prantl, ii, 3, p. 154, K.} 

 (Mexico ; Argentina) ; probably in N. Patagon. 



