Trees of New York State 21 



For the derivation of scientific names used in the text, the 

 reader is referred to the glossary' on page 407. 



Varietal names, where necessary, follow the same plan as 

 specific names, and take the same endings. They are written 

 thus: Be tula aiha, var. papyrifera. 



CLASS FICATION OF ARBORES: ENT PLANTS 



With the excejition of a few tree ferns which are classed 

 among the Pteridophytes and restricted to tropical habitats, 

 arborescent plants are confined to the Spermatophytes and are 

 represented by both Gymnosperms and Angiosperms. The 

 dendroid Gymnosperms which are of economic importance as tim- 

 l)er producers are restricted to the order Coriiferales although 

 Gingko and some of the Cycads become arborescent. Angio- 

 sperms include many monocotyledonous and dicotyledonous 

 species which become trees and grow under manifold conditions 

 and habitats. These are arranged, according to the usual scheme 

 of classification, successively in orders and families. A somewhat 

 arbitrary grouping of the orders into larger artificial divisions, 

 lor the sake of convenience, tends for greater clearness and ren- 

 ders the approach to the subject of Dendrology easier for the 

 novice. Arborescent Pteridophytes and Monocotyledons are 

 omitted as not being representative of temperate regions. The 

 arborescent plants of the north temperate zone may be grouped 

 roughly as follows : 



(1) Coniferae (one order). 



(2) Amentiferae (six orders). 



(3) Floriferae (twenty-two orders). 



Coniferae are characterized by (a) leaves which are usually 

 evergreen, (b) seeds borne naked in cones or terminally without 

 cone formation, (c) excurrent trunks, (d) wood without ducts 

 or pores. Represented by forty genera and some 350 species, 

 grouped under two families in the order Coniferales. 



Amentiferae are characterized by (a) flowers inconspicuous, 

 borne in aments, (b) fruit cupiliferous and generally a nut, (c) 

 generall}' deliquescent trunks, (d) wood with ducts or pores. 

 Represented by twenty -two genera grouped in six orders. 



Floriferae are characterized by (a) typical flowers which are 

 showy and not borne in aments, (b) fruit not cupiliferous and 



