CHAPTER V 



A SYSTEMATIC ENUMERATION OF THE CONIFERS 

 CULTIVATED IN NORTH AMERICA 



THE group of plants known as conifers, popularly often 

 called evergreens, belongs, together with the Cycads and 

 Gnetacese, to the division of Gymnosperms which is 

 chiefly distinguished from the other phenogamous plants or 

 Spermatophytes by the ovules not being inclosed in an ovary. 

 The conifers are now usually divided into three families of 

 which the first, Ginkgoaceae, the Ginkgo family, is closely re- 

 lated to the Cycads in its mode of fertilization, which is by 

 motile sperm-cells, while in the Taxaceae and Pinaceae, fertiliza- 

 tion is effected by means of passive sperm-cells developing long 

 pollen-tubes as in the other phenogamous plants. The Taxa- 

 ceae differ from the Pinaceae chiefly in the fertile flower, which 

 consists of few or only one carpel with one or two ovules 

 developing into a drupe-like seed usually exceeding the carpels, 

 while in the latter family the flower consists of usually nu- 

 merous carpels and develops into a cone-like fruit with mostly 

 winged seeds inclosed between the carpels. 



All the conifers are woody plants, sometimes attaining great 

 dimensions. They inhabit chiefly the colder and temperate 

 regions of the globe where they usually form the predominant 

 components of the forests. Among them are the most important 

 timber trees of the northern countries, and as ornamental trees 

 they are particularly valuable in colder sections as they are the 

 only evergreens attaining to a large size and are indispensable 

 for the creation of evergreen woods and shelter-plantations. 



The scope of this work does not permit the bringing out of 



