Trees of New York State 351 



CLASS II. ANGIOSPERMAE 



PLANTS WITH OVULES ENCLOSED IN AN OVARY 



Flowering plants in which the ovules are borne enclosed in an 

 ovary which remains closed in fruit or dehisces to set free the 

 seeds. This class includes the great bulk of the typical flowering 

 plants which number approximately 125,000 species and are widely 

 spread over the earth wherever plants grow. The essential feature 

 of the group which separates it from Gymnosperms is the presence 

 of the pistil in the flower in addition to stamens. Angiosperms 

 are of more recent origin than Gymnosperms and comprise both 

 herbaceous and woody types. 



Angiosperms are divided into two sub-classes which are char- 

 acterized, viz. : 



Dicotyledons have (a) lateral cotyledons (generally two) ; (b) vascular 

 bundles or tissue in a ring; (c) open venation; (d) 4- or 5-merous flowers. 



Monocotyledons have (a) a single terminal cotyledon; (b) vascular bundles 

 scattered in the stem; (c) closed venation; (d) 3-merous flowers. 



Dicotyledons includes among their numbers herbs, shrubs and trees, and 

 arborescent forms which are found in all regions from beyond the Arctic Circle 

 to the Equator. Arborescent monocotyledons are confined to warm climates 

 and are represented by Palms, Yuccas, etc., some of which grow in the 

 warmer parts of the United States. 



Subclass 1. DICOTYLEDONS 



The Dicotyledons number about 100,000 species and comprise 

 by far the greater part of the flowering plants. All of the arbo- 

 rescent plants of northern regions, with the exception of the 

 coniferous trees, are included in this group which is interspersed 

 with many herbaceous forms. Dicotyledons are more primitive 

 than Monocotyledons and are thought to have been derived from 

 ancestral forms of Gymnosperms during the lower Cretaceous. 



Series 1. APETALAE 



Dicotyledons in which the corolla is wanting ; calyx may or may 

 not be present. 



WILLOW FAMILY. SALICACEAE 

 Trees or shrubs wdth brittle twigs, alternate, simple leaves, 

 aments of dioecious flowers, soft light wood, and bitter bark. The 



