GLOSSARY 



663 



Tuber, a relatively short, thickened 

 rhizome with numerous buds. 



Tunica, the peripheral layer or layers 

 of the apex of the shoot. 



Tylose, the intrusion of a protoplast 

 into a vessel. 



Umbel, a flower cluster in which the 

 pedicels arise at about the same level 

 on the peduncle. 



Umbellet, a secondary umbel. 



Undulate, with a wavy surface. 



Vacuolar membrane, the limiting 



membrane separating the cytoplasm 



from an enclosed vacuole. 

 Vacuole, a cavity in the cytoplasm 



containing cell sap. 

 Ventral, applied to the anterior or 



inner face of an organ. 



Vernation, the arrangement of leaves 

 in a bud. 



Versatile, (of anther) attached near 

 the middle and turning freely on its 

 support. 



Vessel, see Trachea. 



Vessel segment, one of the cells com- 

 prising a vessel. 



Whorl, an arrangement of leaves or 

 floral parts in a circle around the stem . 



Xylem, a complex vascular tissue which 

 may include tracheids, vessels, fibers, 

 parenchyma, and frequently ducts or 

 glands. 



Zygomorphic, (of flower) capable of di- 

 vision in only one plane of symmetry. 



Zygote, the product of the union of 

 two gametes; a fertilized egg. 



