1990 



A TEXTBOOK OF THEORETICAL BOTANY 



the name of Wood Lilies owing to their preference for shady positions. 

 T. declinatiim and T. acuminatum both produce white flowers in April on 

 stalks about 9 in. high, which arise singly from the rhizome. The genus 

 Paris contains twenty species, of which P. quadrifolia (Fig. 1920) (Herb 

 Paris) is found wild in Britain. The rhizome gives rise to aerial stems with 

 a whorl of four or more net-veined leaves and solitary tetramerous flowers 

 which are protogynous and are pollinated by flies. 



The Pontederiaceae are a small group of herbaceous water plants 

 which either grow erect in the mud or are free floating. The only important 

 genus is Eichhornia, species of which are cultivated in hot-houses in this 

 country. E. speciosa (Fig. 1921) has swollen petioles which act as floats 

 and support the plant on the surface of the water. The showy violet or 

 white spikes have earned the plants the name of Water Hyacinths. They 

 constitute very troublesome water weeds because of their rapid vegetative 

 propagation and the ease with which they can be blown about on the 



Fio. 1 92 1. — Eichlwrnia speciosa. Water Hyacinth. I-loatiiiK plants. Brazil. 



