256 GLOSSARY 



Thal'lus. A mass of cellular tissue, usually in the form of a flat stratum or 



expansion, instead of stem and leaves. 

 Tri'chome. A hair on the surface of a leaf or stem, or any modification of 



a hair. 

 Tu'ber. A fleshy underground stem, or branch, with buds. 



Um'bel. An inflorescence in which the pedicels all spring from the same 

 point, like the ribs of art umbrella. 



Veins. The system of branching vascular woody tissue seen in leaves. 



Xy'lem. That portion of a fibro-vascular bundle developed into wood cells. 



Zo'o-spore. A spore provided with one or more slender cilia, by the vibra- 

 tion of which it swims in the water. 



