SYNOPSIS 



OF THE FAMILIES AND GENERA REPRESENTED IN THIS WORK WITH 



ANALYTICAL KEYS 



LEADING TO THE SPECIES. 



CLASS I. GYMNOSPERM^. 



The class of plants known as Gi/miiuspcniiw is of very ancient origin, being represented 

 among the fossils of the Silurian Age and most numerously among those of the Triassic. It is 

 now represented by not more than 'four hundred and fifty species, which have the following 

 characters in common : They are flowering plants in which the ovules or seeds are borne 

 naked upon an open scale (not inclosed in an ovary) and are trees and shrubs mainly with 

 resinous juice, chiefly parallel-veined leaves and stems, consisting of bark, wood and pith, 

 increasing in thickness by annual layers of the wood externally and of the bark internally. 

 It consists of three families, viz. : Comferce, Genetacecc and Cycaclaccw. the latter two being 

 confined chiefly to tropical and south temperate regions. 



PINE FAMILY. CONIFERS. 



A family of trees and few shrubs with resinous juice and cell-walls of wood marked with 



circular discs. It is of greatest economic value and world-wide distribution, but chiefly in 



north temperate regions. Among its representatives are trees, notably the Sequoias, which 



are considered to be of the greatest longevity of all living organisms. It consists of thirty-one 



genera of which thirteen are represented in the United States. 



Leaves narrow or scale-like, clustered or alternate, parallel-veined and generally persistent: 

 buds scaly. Flowers in catkins or solitary with an involucre of enlarged bud-scales, unisexual 

 and monajcious (dioecious in Jnniperus) destitute of calyx and corolla; anthers 2-celled ; 

 pistillate flowers bearing on the inner face of each scale 2 or more ovules and becoming in 

 Fruit a woody cone or rarely a. berry or drupe; seeds often winged, with coat of two layers; 

 embryo axial in copious albumen ; cotyledons 2 or several. 



KEY TO THE GENERA. 



a Scales of cones in the axils of persistent bracts, numerous, spirally arranged and each bearing 

 at its base above 2 seeds {Ahietinece) . 

 b Cones requiring 2 years to mature ; leaves needle-shaped in 2-5-leaved axillary fascicles 

 (solitary in one species) sheathed at base with membranous scales, persistent. 



Pinus. 

 V Cones maturing in one season ; leaves 



o In many-leaved fascicles on lateral spurs, deciduous Lai'ix. 



c^ Solitary, scattered, persistent and linear or 4-sided ; cones 



d Pendent and scales persistent on the axes ; branchlets rough with woody persistent 

 bases of the leaves 

 e Leaves sessile, 4-sided or flattened above and stomatiferous all sides or above only. 



Picea. 



e^ Leaves petiolate, flattened and stomatiferous below only Tsuga. 



d^ Erect on the branchlets and scales falling away from persistent axes at maturity ; 



leaves leaving flat or depressed leaf-scars Abies. 



a^ Scales of the cones without bracts 



b Numerous, spirally arranged and forming a woody cone; leaves linear (sometimes scale- 

 like ) alternate ( Taxodiw) and deciduous Taxodium. 



b- Few, decussate; leaves decussate or in 3-ranks and often of 2 forms {Cupressinew) ; 

 fruit a 

 c Woody cone ; leaves all scale-like ; cones 



[4181 



