MODE OF LIFE IN ANNUALS AND BIENNIALS. 27 



height of a man. And if they reach this size, it is not as a single main trunk, but 

 by a cluster of stems all starting from the ground. 



^6. Trees are woody plants rising by a trunk to a greater height than shrubs. 



67. Herbs are divided, according to their character and duration, into Annuals, 

 Biennials, and Perennials. 



68. Annuals grow from the seed, blossom, and die all in the same season. In 

 this chmate they generally spring from the seed in spring, and die in the autumn, 

 or sooner if they have done blossoming and have ripened their seed. Oats, Barley, 

 Mustard, and the common Morning- Glory (Fig. 4) are familiar annuals. Plants 

 of this kind have fibrous roots, i. e. composed of long and slender threads or fibres. 

 Either the whole root is a cluster of such fibres, as in Indian Corn (Fig. 48), Barley 

 (Fig. 56), and all such plants ; or when there is a main or tap root, 

 as in Mustard, the Morning-Glory, &c., this branches off into slen- 

 der fibres. It is these fibres, and the slender root-hairs which are 

 found on them, that mainly absorb moisture and other things from 

 the soil ; and the more numerous they are, the more the plant can 

 absorb by its roots. As fast as nourishment is received and pre- 

 pared by the roots and leaves, it is expended in new growth, par- 

 ticularly in new stems or branches and new leaves, and finally in 

 flowers, fruit, and seed. The latter require a great deal of nour- 

 ishment to bring them to perfection, and give nothing back to the 

 plant in return. So blossoming and fruiting weaken the plant very fibrous rom.. 

 much. Annual plants usually continue to bear flowers, often in great numbers, 

 upon every branch, until they exhaust themselves and die, but not until they have 

 ripened seeds, and stored up in them (as in the mealy part of the grain of Com, 

 &c.. Fig. 44, 45) food enough for a new generation to begin growth with. 



69. Biennials follow a somewhat different plan. These are herbs which do not 

 blossom at all the first season, but live over the winter, flower the second year, and 

 then die when they have ripened their seeds. The Turnip, Carrot, and Parsnip, 

 the Beet, the Radish (Fig. 57), and the Celandine, are familiar examples of bien- 

 nial plants. I 



70. The mode of life in biennials is to prepare and store up nourishment through 

 the first season, and to expend it the next season in flowering and fruiting. Accord- 

 ingly, biennials for the first year are nearly all root and leaves ; these being the 

 organs by which the plant works, and prepares the materials it hves on. Stem 



