TERM OK PERIOD OF PLANT LIFE. 17 



42. Monocarpic herbs. The Century-plant (Agave), the Talipot-palm, etc., are so called. 

 They vegetate, bearing leaves only, for many years, accumulating materials and strength 

 for one mighty effort in fructification, which being accomplished, they die. In some 

 ppecies the term of life depends on climate alone. The Castor-bean (Ricinus) is an annual 

 herb in the Northern States, a shrub in the Southern, and a tree of large size in its native 

 India. So Petunia, annual in our gardens, is perennial at home (in Brazil). 



43. Perennial plants are such as have an indefinite duration 

 of life, usually of many years. They may be either herbaceous 

 or woody. Herbaceous perennials, or perennial herbs (2), are 

 plants whose parts are annual above ground and perennial below. 

 In other words, their roots or subterranean stems live from year 

 to year, sending up annually, in Spring, flowering shoots which 

 perish after they have ripened their fruit in Autumn ; as the Lily, 

 Dandelion, Hop. 



44. Woody perennials usually vegetate several years, and at- 

 tain well-nigh their ordinary stature before flowering; thence- 

 forward they fructify annually, resting or sleeping in winter. 

 They are known as trees (b), shrubs (b), bushes, and under- 

 shrubs (b) distinctions founded on size alone. 



45. A shrub (b) 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 bush (Snowball, Andromeda). If 

 still smaller, it is an undershrub (b) (Whortleberry). 



46. A tree (b) 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. 



47. As to age, some trees live only a few years, rapidly attaining their growth and rap- 

 idly decaying, as the Peach ; others have a longevity exceeding the age of man ; and some 

 species outlive many generations. Age may be estimated by the number of wood-circles 

 or rings seen in a cross-section of the trunk (403), each ring being (very generally) au 

 annual growth. Instances of great longevity are on record. See Class Book of Botany, 

 99, 100. The monarch tree of the world is that California!! Cedar Sequoya gigantea. 

 One which had fallen measured 2G feet in diameter, and 363 in length ! The wood-cir- 

 cles of this specimen are unusually thick, yet count up to 1,330 years. Among those yet 

 standing (A. D. 1866), are many of even greater dimensions, as beautiful in form as they 

 are sublime in height the growth, probably, of more than 2,000 years. 



48. Trees are again distinguished as deciduous (b) and ever- 

 green (5) the former losing their foliage in Autumn, and re- 

 maining naked until the following Spring; the latter retaining 



