GLOSSARY 263 



Variety. A subdivision of a species. 



Vein. A fibro-vasciilar bundle of a leaf, petal, or other thin anrl flat 



organ. 

 Venation. The manner in which veins are distributed. 

 Venter. The swollen basal portion of an archegonium containing the egg. 

 Vernation. The manner of unfolding in buds. 

 Vessel. A tube or duct made of separate sections but continuous from 



the absorption of the cross partitions. The walls have various 



thickening deposits, often spiral or ring-formed. 

 Volva (a wrapper). An envelope inclosing a young toadstool and ruj>- 



tured by the growth of the latter, portions sometimes remaining as 



scales on the top of the cap and sometimes as a cup at the base of 



the stalk. 



Xeroph3i;e (dry plant). A plant which can live with a scanty supply of 



water. 

 Xylem (wood). The wood or inner part of a fibro-vascular bundle, the 



portion within the bundle cambium. 



Zone. In ecology a band of any given plant formation, usually bounded 



by other bands representing other formations, as about a pond, a 



salt spring, etc. 

 Zoospore (animal spore). A ciliated and therefore motile asexual spore. 

 Zygomorphism (yoke form). The arrangement of parts in corresponding 



light and left halves ; bilateral symmetry. 

 Zygospore (yoke spore). A sexually formed spore resulting from the 



fusion of similar gametes (isogamy) ; also called a zygote. 



