INTRODUCTION. 



by a reticulated structure of all their parts, admits of portions 

 of its leaves being broken off, without impeding the remain- 

 der of the leaf in the performance of its functions; while 

 the tulip, belonging to a division characterised by a parallel 

 fibrous structure of all the parts, does not admit of part of 

 the leaves, and particularly of their extremities, being cut off, 

 without impeding their functions, and consequently injuring 

 the present. health of the plant, and influencing its vigour 

 for the following year. But any one who is so far a vegeta- 

 ble anatomist and physiologist as to know the distinctive 

 structures of these two divisions (Monocotyledoneae and Di- 

 cotyledon eae), if he should see only a part of the leaf of a 

 tulip or of a ranunculus, would be able to ascertain the divi- 

 sion to which it belonged, and, by consequence, the essential 

 principles of the culture and management of the plant, as far 

 as respects the most important organs of plants, leaves being 

 analogous to the lungs of animals. 



Such is the difference between knowing a plant as a gar- 

 dener or an amateur, and knowing it as a physiologist* 

 There must evidently be a superior degree of pleasure in 

 combining both descriptions of knowledge, and as evidently 

 an advantage in point of utility : for though the mere culti- 

 vator might be aware of the effect of cutting or mutilating 

 the leaves of the tulip and ranunculus from experience in 

 the management of these two plants, yet not knowing it from 

 principle, the knowledge could only be of use to him in this 

 particular case, instead of being of use as applied to two of 

 the three grand divisions of the vegetable kingdom. 



There is a positive source of pleasure in knowing the 

 species of plants individually. ' Every plant of which we 

 acquire a knowledge by sight, so as to be able to recog- 

 nise it again when it comes in our way, is not only a dis- 

 tinct source of pleasure at first, but the pleasure is repeated 

 and increased when we see it for the second and third 

 times, or after some time, or in other circumstances re- 

 latively to ourselves or to the plant. In this way, with no 

 other knowledge cf plants than that of being able to name 

 them when we see them, and, consequently, to commu- 

 nicate our ideas respecting them to others, they may prove 

 sources of the most interesting associations. But even 

 this pleasure, derived from what may be termed the trivial 

 knowledge of plants, may be greatly enhanced by extending 

 our views to circumstances connected with them not strictly 

 botanical. Thus we may view them with regard to their geo- 

 logical relation in any particular country, their geographical 

 distribution relatively to the world, their migration from one 



