782 



THE NAIAD FAMILY. 



the commonest species, often covering the water to a great extent. 

 Fl. summer, and more easily met with in that state than any other 

 species. 



3. Gibbous Duckweed. Lemna gibba, Linn. (Fig. 910.) 

 (Eng. Bot. t. 1233.) 



Fronds shaped like those of the lesser 

 D., bnt rather larger and much thicker, 

 flat above, spongy and almost hemi- 

 sperical underneath, with a single root 

 to each. Stamens 2. Ovary with 2 or 

 more ovules. 



With the station and range of the 

 lesser D. it is everywhere less common. 

 Hare in England and Ireland, and still 

 FL summer, very rarely. 



more 



Fig. 940 

 so in Scotland. 



4. Greater Duckweed. Lemna polyrrhiza, Linn. (Fig. 941.) 

 (Eng. Bot. t. 2458.) 



Fronds larger than in any other 

 species, attaining 3 or 4 lines diameter, 

 broadly ovate or orbicular, rather thick, 

 with a cluster of roots under each one. 

 Flowers of the gibbous D. 



As widely dispersed as the other 

 species, and rather more frequent than 

 the gibbous D., but much less so than 

 the two others. The flowers appear to 

 have been but once observed. 



Fig. 911. 



LXXVII. THE NAIAD FAMILY. NAIADES. 



Aquatic floating or submerged plants ; the leaves either sheath- 

 ing at the base or accompanied by sheathing stipules, alternate or 

 sometimes opposite. Flowers axillary, inconspicuous, solitary or 

 spiked, usually proceeding from a sheathing bract. Perianth none, 

 or consisting of 4 small, scale-like segments. Stamens 1, 2, or 4. 



