MONOCOTYLEDONS 



417 



COMMELINACEAE (SPIDERWORT FAMILY) 

 TRADESCANTIA (SPIDERWORT) 



Habitat and habit. The spiderworts are among the commonest 

 wild and cultivated plants of the spring and summer flora. They 

 usually inhabit gravelly, sandy, or alluvial soils in woods or along 

 railroads and river 

 banks. In Trades- 

 cantia virginiana 

 (Fig. 265) the stem 

 is both aerial and 

 subterranean. The 

 aerial stem bears 

 the long, parallel- 

 veined leaves and 

 blue flowers char- 

 acteristic of the 

 species. The un- 

 derground stem is 

 tuberous and gives 

 rise to one or more 

 lateral flowering 

 shoots by means 

 of lateral buds. It 

 also enables the 

 plant to live over 

 the late summer, 

 autumn, and 



Vascular 

 bwndle 



A, plant in flower; B, reproductive structures and stem 

 section (a, front view of flower; b, ground plan; c, dehis- 

 cent fruit ; d, section of stem) ; C, leaf and parallel venation 



FIG. 264. Habit and reproduction of the common 



spiderwort ( Tradescantia) 

 win- 

 ter, furnished with 

 buds and reserve 

 food for the early spring growth. Tradescantia is thus a semi- 

 xerophyte or semitropophyte, like many of the cultivated bulbous 

 monocotyledons. 



Reproduction. The blue or purple flowers are ephemeral, that 

 is, lasting for a day only, and have their parts arranged in threes 

 (Fig. 264, J5) like other typical monocotyledons, 



