An Illustrated Flora of the Northern United States, Canada and the British Possessions/Gymnospermae
|An Illustrated Flora of the Northern United States,
Canada and the British Possessions
by Nathaniel Lord Britton & Addison Brown
|Class 2. Angiospermae
Class 1. Gymnospérmae.
Ovules (macrosporanges) naked, not enclosed in an ovary, this represented by a scale or apparently wanting. Pollen-grains (microspores) dividing at maturity into two or more cells, one of which gives rise to the pollen-tube (male prothallium), which directly fertilizes an archegone of the nutritive endosperm (female prothallium) in the ovule.
The Gymnosperms are an ancient group, first known in Silurian time. They became most numerous in the Triassic age. They are now represented by not more than 500 species of trees and shrubs.
There are three orders, Coniferales, Cycadales and Gnetales, the first of which is represented in our area by the Pine and Yew Families.
|1. Pinaceae||Pine Family|
|2. Taxaceae||Yew Family|