INTRODUCTION. XV 



fore Cellular ; so that the inquiry of the student, instead of being 

 directed in the first instance to an obscure but highly curious micro- 

 scopical fact, is at once arrested by the two most obvious peculiarities 

 of the vegetable kingdom. 



Among vascular plants two great divisions have been formed ; the 

 names of which, Monocotyledons and Dicotyledons, are derived from 

 the former having usually but one lobe to the seed, and the latter 

 two, — a structure much more difficult to ascertain than the presence 

 or absence of spiral vessels, and more subject to exceptions. But no 

 botanist would proceed to dissect the seed of a plant for the purpose 

 of determining to which of these divisions it belonged, except in 

 some special cases. We know that the minute organisation of the 

 seed corresponds with a peculiar structure of the stem, leaves, and 

 flowers, the most highly developed, and most easily examined parts 

 of vegetation ; a botanist, therefore, prefers to examine the stem, 

 or the leaf of a plant, to see whether it is a Monocotyledon or a 

 Dicotyledon, and does not find it necessary to anatomise the seed. 



The presence or absence of albumen, the structure of the embryo, 

 the position of the seeds or ovula, the nature of the fruit, the modi- 

 fications of the flower, will, I presume, be hardly brought forward as 

 other difficult points for the student of the Natural System, because, 

 whether the one system or the other be employed, he must make 

 himself acquainted with such facts, for the purpose of determining- 

 genera. The common Toad-flax cannot be discovered by its cha- 

 racters in any book of botany, without the greater part of this kind 

 of inquiry being gone through. 



In the determination of genera, however, facility is entirely on 

 the side of the Natural System. Jussieu has well remarked, " that 

 whatever trouble is experienced in remembering, or applying the 

 characters of natural orders, is more than compensated for by the 

 facility of determining genera, the characters of which are simple in 

 proportion as those of orders are complicated. The reverse takes 

 place in arbitrary arrangements, where the distinctions of classes and 

 sections are extremely simple and easy to remember, while those of 

 genera are in proportion numerous and complicated." 



Let me not, however, be misunderstood in what I have been 

 saying of the s?/pposec? difficulties of the Natural System. Far be it 

 from me to state that there are no difficulties for the botanical student 

 to overcome ; on the contrary, there is no science which demands 

 more minute accuracy of observation, more patient research, or a 

 more constant exercise of the reasoning faculties, than that of Botany. 

 But no subject of human inquiry can be pursued loosely and usefully 

 at the same time; for we may rest assured, that that which can be 

 studied superficially is little deserving of being studied at all. 



