224 BOTANY. 
tree-ferns. They are of slow growth and are long-lived; 
the stem elongates by a slowly unfolding terminal bud, 
which gives rise to a crown of widely spreading pinnate 
leaves, which are constantly renewed above as they die and 
fall away below. About seventy-five species are now 
known, all confined to tropical or sub-tropical climates. In 
geologic times (Triassic and Jurassic) they were very abun- 
dant. 
473. The Conifers (Order Conifer) are mostly trees of 
a considerable size, with branching, spreading, or spiry 
tops, as the pines, spruces, firs, etc. ete. They are gener- 
ally of rapid growth, and in many cases attain a great 
height and diameter. In the greater number of species the 
leaves are persistent, and the trees, consequently, evergreen. 
474, The order contains thirty-two genera and about 
three hundred species, which are distributed mainly in the 
cooler climates of the globe. Seventy or more species 
occur within the limits of the United States, and constitute 
in many places enormous forests hundreds of miles in ex- 
tent. 
~ 
The pines (Pinus) include the most important trees of the order. 
The White pine (P. strobus), formerly very abundant from the Great 
Lakes eastward, furnishes the greater part of the ‘‘ pine lumber” so 
largely used in the Northern States for building and other purposes. 
The Sugar-pine (P. lambertiana) of California resembles the White 
pine but is much larger, being often 60 to 90 metres (200 to 300 fect) 
in height, with a trunk 8 to 6 metres (10 to 20 feet) in diameter. The 
Southern pine (P. australis), abundant from the Carolinas to Texas, is 
a tree of moderate dimensions, whose hard wood is ‘‘ superior to that 
of any other North American pine,” and is known in the markets as 
Yellow or Georgia pine. Scotch pine (P. sylvestris) and Austrian 
pine (P. laricio), both natives of Europe, are extensively planted in 
this country. Besides the spruces, firs, larches, cedars, and many 
other well-known trees, the order contains the two species of great 
Redwoods. The most remarkable is called the Big ‘Tree (Sequoia 
