NORTH AMERICAN ANGIOSPERMS - INTRODUCTION

"Angiosperm" translates to "covered seed," in contrast to naked seed for gymnosperms, and most angiosperms are referred to as 'flowering plants.'  They are a much more recent evolutionary development, dating back only 140 million years ago (relative to gymnosperms at 350 million years) but far outnumber the gymnosperms in terms of species richness, distribution, and complexity of plant forms and adaptations.  This makes angiosperms crucial to the course because of their diversity and ecological roles, as well as many having commercial value for lumber.

Angiosperms are separated broadly into "monocots"  and "dicots."  Monocots have a single cotyledon (storage tissue for the seeds) and are dominated by the grasses, palms, bamboos and yuccas.  Dicots (multiple cotyledons - beans have two that separate easily with your thumbnail) are dominated by herbs, vines, shrubs and TREES.  There are tree-form monocots like the palms in southern California and "tree ferns" in other parts of the world, but they don't have woody stems (secondary xylem and phloem) and therefore aren't trees. 

Angiosperms, in total, include about 405 families and about 250,000 species that range from the hottest, wettest tropics to the harshest deserts to the coldest arctic environments.  Fortunate for students in this class, 'broadleaved trees' are found in only about 47 of those families and only 17 families are significant to forestry in temperate and boreal parts of North America.  These 17 families contain several hundred tree species but the course list is limited to about 70 species of particular significance.

Families:

Angiosperm FAMILIES & GENERA

Angiosperm SPECIES LIST

Angiosperm EXAM STUDY GUIDE