Roots. , 175 



digesting what is proper for the plant ; they have little sentinels 

 at the doors which reject improper and poisonous substances. 

 The life-power, in many instances, holds a close analogy with 

 the mind, and like it, what is offensive at first, may, by continual 

 repetition, become at last agreeable, and even sometimes neces- 

 sary ; we have a good example of this in the influence of tobacco, ' 

 opium, and many other articles on the human frame, which fur- 

 nishes instances of what is called Tolerance of the Vital Powers. 

 Dr. Mitchell, of this city, had some peaches sent to him which 

 were perfeclly salt; some brine had been accidentally thrown at 

 the base of the tree ; the salt bribed the sentinels, as it were, to 

 admit its particles, and it thus became universally disseminated 

 even in its fruit. Alcohol has found entrance into the drunk- 

 ard's veins, and when drawn from the arm has been ignited by 

 a torch. These, of course, are rare instances, yet answer to 

 illustrate the general principle. The root is that portion of the 

 embryo called its descending axis, which, when acted upon by 

 the same influences as the stem, goes downwards, while the othe* 

 ascends. Like an icicle, as a general rule, they increase in length, 

 by the addition of new matter to their extremities, which, of 

 course, is furnished from within, and not like the freezing par- 

 ticles, from without. 



With respect to duration, roots are either annual, biennial, or 

 perennial. As roots are reservoirs of nourishment for the plant, 

 which is expended in its growth, when it happens that the plant 

 consumes its supply as fast as it is elaborated, and ripens seed, 

 that most exhausting process to a plant, it has nothing after this 

 is done to afford it sustenance, and consequently dies the same 

 year it springs up ; such plants are termed annual. But there is 

 another kind which lays up a large store, and by not flowering, 

 or even spending much in the way of stems and branches, hav- 

 ing oftentimes but a mere bunch of leaves above, the surface of 

 the ground to assist the working up of the food, waits the second 

 year, when its growth is remarkably rapid and vigorous, shooting 

 forth a large stem, and bearing flowers and fruit, and having 

 consumed all its capital, perishes like its predecessor — these are 

 termed biennial. The third class or perennial, while one por- 

 tion is consuming, is busily employed in laying up a store for 

 the ensuing year, and thus continues to live a long while. 



The first class, or annual plants, have always branching, fibrous 



