49 



EXPLANATION OF TERMS. 



Wendungszellen. In Characeae : disc- 

 shaped group of hyaline cells or single 

 cell at base of oosphere. 



Wrapper. Same as volva. 



Xylem. Region of a vascular bundle or of 

 an axis with secondary thickening which 

 contains tracheae. Comp. phloem. 



Zoidiophilous. Pollinated by the agency 

 of animals. See entomophilous. Comp. 

 anemophilous, hydrophilous. 



Zoogamete. Same as planogamete. 



Zoogloea. Colony of Schizomycetes im- 

 mersed in a gelatinous substance formed 

 by the walls of their cells. 



Zoogonidium. Motile gonidium. 



Zoosporangium. Sporangium producing 

 zoospores or zoogametes. 



Zoospore. A motile spore. Applied fre- 

 quently to a planogamete. 



Zygomorphous. Flowers divisible into 

 similar halves in only one plane are termed 

 by Braun zygomorphous. Sachs extends 

 the term to cases where bisection into 

 similar halves is possible in two planes 

 at right angles to one another, the halves 

 of one section being different from the 

 halves of the other. Same as monosym- 

 metrieal. Comp. actinomorphous. 



Zygospore. Spore formed by conjugation 

 of two similar gametes. 



Zygote. General term for the product of 

 the coalescence of two gametes. 



Zygozoospore. A motile zygospore. 



