EVOLUTION 



8l 



of Wolffia possess still simpler bodies, somewhat globose, 

 with neither roots, veins, nor other organs, except flowers; 

 even flowers are unknown in some species (e.g., Wolffia 

 populifera, Fig. 44). Wolffia punctata measures only 

 0.5-0.8 mm. long. The plants are fittingly described in 

 the manuals as "minute, alga-like grains," floating on or 



FIG. 44. Lemnaceae. a, b, c, Lcmna trisulca; d, Wolffia punctata; 

 e, f, Wolffia papulifera. (Redrawn from Britton and Brown, slightly 

 modified.) 



just beneath the surface of still water. Some botanists 

 consider the plant body as morphologically a frond, others 

 as a leafless stem. Since the first plant-body from the seed 

 is only a matured cotyledon, or seed-leaf , Goebel considers 

 that it cannot be interpreted as other than a free-living 

 leaf. These tiny, simple plants are considered to have 



