262 THE OPEN BOOK OF NATURE 
Trilobites : An extinct order of crustaceans. 
Tripinnate : Three times pinnate. 
Tuber : An underground fleshy development of the stem, as in 
the potato. 
Tyrannosaurus ;: An extinct reptile. 
Unicellular : One-celled. 
Vasculum : A collecting-box for plants. 
Viscid : Sticky, tenacious, clammy. 
Viviparous : Producing young alive. 
Volcanic : Igneous rocks which have cooled at or near the surface 
of the earth. 
Whorl : Leaves, flowers, or organs arranged in a circle round an 
axis. 
