TERM OF PLANT LIFE. 21 



parts arc annual above ground and pcrorinial below. In other words, 

 their roots or subterranean stems live from year to year, sending up an- 

 nually in spring flowering shoots, which perish after they have ripened 

 their fruit in autumn ; as the lily, dandelion, hop. 



94. Woody; perennials usually vegetate several years, and attain 

 well nigh their ordinary stature before flowering; thenceforward they 

 fructify annually, resting or sleeping in winter. They are known as 

 trees, shrubs, bushes and undershrubs — distinctions founded on size alone. 



95. A shrub is a diminutive tree, limited to eighteen or twenty feet 

 in stature, and generally dividing into branches at or near the surface of 

 the ground (alder, quince). If the woody plant be limited to a still 

 lower growth, say about the human stature, it is called a busk, (snow-bali, 

 Andromeda.) If still smaller, it is an undershrub (whortleberry). 



96. A tree is understood to attain to a height many times greater 

 than the human stature, with a permanent woody stem, whose lower 

 part, the trunk, is unbranched. 



9*7. Longevity of trees. Some trees live only a few years, rapidly 

 attaining their growth and rapidly decaying, as the peach ; others have 

 a longevity exceeding the age of man, and some species outlive many 

 generations. 



98. The age of a tree may be estimated by the number of wood- 

 circles or rings seen in a cross section of the trunk (§ 667), each ring 

 beiag (very generally) an annual growth. 



99. Examples. The known ago of an elm, as stated by De Candolle, was 335 

 years; of a larch, 576; a chestnut, COO; an orange, 630; oaks, from 810 to 1500; 

 yews, 1214 to 2820. — 



100. Adanson estimated the age of the baobabs of Africa at 5000 years. Liv- 

 ingston reduces it to 1800. The yew trees of Britain, as described by Balfour, are 

 of wonderful longevity. One in Bradburn church-yard, Kent, is 3000 years old, 

 and the great yew at Hedsor, Bucks, twenty-seven feet in diameter, has vegetated 

 3200 years. 



101. Magnitude. At the first establishment of Dartmouth College, a pine tree 

 was felled upon the college plain which measured 210 feet in height In the Ohio 

 Valley the red maple attains a girth of 20 feet, the tulip-tree of 30, and tne syca- 

 more of more than 60- But the monarch tree of the world is the Sequoya gigantoa 

 — the California pine. One which had fallen measured 31 feet ia diameter, and 363 

 feet in length. Among those yet standing are some of still greater dimensions, as 

 beautiful in form as they are sublime in height, the growth (as estimated by the 

 wood-circles) of more than 3000 years. > 



' 102. Trees are again distinguished as decidous and evergreen — tho 

 former losing their foliage in autumn and remaining naked until the 

 following spring ; the latter retaining their leaves and verdure through- 

 out all seasons. The fir tribe (Coniferae) includes nearly all the ever- 

 greens of the North ; those of the South are far more numerous in kiiid, 

 e. g.> the magnolias, the live-oaks, holly, cherry, palmetto, &c. 



